next up previous
Next: IRAM Astronomy Postdoctoral Position Up: IRAM Newsletter 72 (February 2009) Previous: Matt Carter in memoriam


Scientific Results in Press

Self-Regulated Fueling of Galaxy Centers: Evidence for Star Formation Feedback in IC 342's Nucleus

Eva Schinnerer$(^{1})$, Torsten Böker$(^{2})$, David S. Meier$(^{4,5})$ and Daniela Calzetti$(^{6})$
$(^{1})$Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany, $(^{2})$European Space Agency, Department RSSD, Keplerlaan 1, 2200 AG Noordwijk, Netherlands, $(^{3})$David S. Meier is a Jansky Fellow of the NRAO, $(^{4})$National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA, $(^{5})$Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA

Using new, high-resolution interferometric observations of the CO and HCN molecules, we directly compare the molecular and ionized components of the interstellar medium in the center of the nearby spiral galaxy IC 342, on spatial scales of $\sim 10$ pc. The morphology of the tracers suggests that the molecular gas flow caused by a large-scale stellar bar has been strongly affected by the mechanical feedback from recent star formation activity within the central 100 pc in the nucleus of the galaxy. Possibly, stellar winds and/or supernova shocks originating in the nuclear star cluster have compressed, and likely pushed outward, the infalling molecular gas, thus significantly reducing the gas supply to the central 10 pc. Although our analysis currently lacks kinematic confirmation due to the face-on orientation of IC 342, the described scenario is supported by the generally observed repetitive nature of star formation in the nuclear star clusters of late-type spiral galaxies.

Appeared in ApJ 684, L21

HI and CO in the circumstellar environment of the oxygen-rich AGB star RX Lep

Y. Libert$(^{1})$, T. Le Bertre$(^{1})$, E. Gérard$(^{2})$ and J.M. Winters$(^{3})$
$(^{1})$LERMA, UMR 8112, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France, $(^{2})$GEPI, UMR 8111, Observatoire de Paris, 5 Place J. Janssen, 92195 Meudon Cedex, France, $(^{3})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France

Context. Circumstellar shells around AGB stars are built over long periods of time that may reach several million years. They may therefore be extended over large sizes ($\sim 1$ pc, possibly more), and different complementary tracers are needed to describe their global properties.
Aims. We set up a program to explore the properties of matter in the external parts of circumstellar shells around AGB stars and to relate them to those of the central sources (inner shells and stellar atmospheres).
Methods. In the present work, we combined 21-cm HI and CO rotational line data obtained on an oxygen-rich semi-regular variable, RXLep, to describe the global properties of its circumstellar environment.
Results. With the SEST, we detected the CO$(2-1)$ rotational line from RXLep. The line profile is parabolic and implies an expansion velocity of $\sim
4.2$ kms$^{-1}$ and a mass-loss rate $\sim 1.7 \times 10^{-7}
\mbox{M$_\odot$}$ yr$^{-1}$ ($d = 137$ pc). The HI line at 21 cm was detected with the Nançay Radiotelescope on the star position and at several offset positions. The linear shell size is relatively small, $\sim$ 0.1 pc, but we detect a trail extending southward to $\sim$ 0.5 pc. The line profiles are approximately Gaussian with an FWHM $\sim 3.8$ km$^{-1}$ and interpreted with a model developed for the detached shell around the carbon-rich AGB star YCVn. Our HI spectra are well-reproduced by assuming a constant outflow ( $\rm\dot{M} =
1.65 \times 10^{-7} \mbox{M$_\odot$}$ yr$^{-1}$) of $\sim 4 \times 10^{4}$ years duration, which has been slowed down by the external medium. The spatial offset of the HI source is consistent with the northward direction of the proper motion measured by Hipparcos, lending support to the presence of a trail resulting from the motion of the source through the ISM, as already suggested for Mira, RSCnc, and other sources detected in HI. The source was also observed in SiO (3 mm) and OH (18 cm), but not detected.
Conclusions. A detached shell, similar to the one around YCVn, was discovered in HI around RXLep. We also found evidence of an extension in the direction opposite to the star proper motion. The properties of the external parts of circumstellar shells around AGB stars should be dominated by the interaction between stellar outflows and external matter for oxygen-rich, as well as for carbon-rich, sources, and the 21-cm HI line provides a very useful tracer of these regions.

Appeared in A&A 491, 789

Coordinated multi-wavelength observations of Sgr A*

Eckart A.$(^{1,9})$, Schödel R.$(^{2})$, Baganoff F.K.$(^{3})$, Morris M.$(^{4})$, Bertram T.$(^{1})$, Dovciak M.$(^{5})$, Downes D.$(^{6})$, Duschl W.J.$(^{7,8})$, Karas V.$(^{5})$, König S.$(^{1,9})$, Krichbaum T.$(^{9})$, Krips M.$(^{10})$, Kunneriath D.$(^{1,9})$, Lu R.-S.$(^{9,1})$, Markoff S.$(^{11})$, Mauerhan J.$(^{4})$, Meyer L.$(^{4})$, Moultaka J.$(^{12})$, Muzic K.$(^{1,9})$, Najarro F.$(^{13})$, Schuster K.F.$(^{6})$, Sjouwerman L.$(^{14})$, Straubmeier C.$(^{1})$, Thum C.$(^{6})$, Vogel S.$(^{15})$, Wiesemeyer H.$(^{16})$, Witzel G.$(^{1})$, Zamaninasab M.$(^{1,9})$, Zensus A.$(^{9})$
$(^{1})$University of Cologne, Zülpicher Str. 77, D-50937 Cologne, Germany, $(^{2})$Instituto de Astrofísica de Andalucía, Camino Bajo de Huétor 50, 18008 Granada, Spain, $(^{3})$Center for Space Research, MIT, Cambridge, MA 02139-4307, USA, $(^{4})$Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA, $(^{5})$Astronomical Institute, Academy of Sciences, Bocdní II, CZ-14131 Prague, Czech Republic, $(^{6})$IRAM, Domaine Universitaire, 38406 St. Martin d'Hères, France, $(^{7})$Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15 24118 Kiel, Germany , $(^{8})$Steward Observatory, The University of Arizona, 933 N. Cherry Ave. Tucson, AZ 85721, USA, $(^{9})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{10})$Harvard-Smithsonian Center for Astrophysics, SMA project, 60 Garden Street, MS 78 Cambridge, MA 02138, USA, $(^{11})$Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, the Netherlands, $(^{12})$Observatoire Midi-Pyrénées, 14, Avenue Edouard Belin, 31400 Toulouse, France, $(^{13})$Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, CSIC, Serrano 121, 28006 Madrid, Spain, $(^{14})$NRAO, PO Box 0, Socorro, NM 87801, USA, $(^{15})$Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA, $(^{16})$IRAM, Avenida Divina Pastora, 7, Núcleo Central, E-18012 Granada, Spain

We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the $\sim 4\times 10^6\mbox{M$_\odot$}$ super-massive black hole (SMBH) at the Galactic Center. The goal of these coordinated multi-wavelength observations is to investigate the variable emission from Sgr A* in order to obtain a better understanding of the underlying physical processes in the accretion flow/outflow. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope (July 2005, May 2007) and the ACIS-I instrument aboard the Chandra X-ray Observatory (July 2005). We report on a polarized NIR flare synchronous to a $8\times 10^{33}$ erg/s X-ray flare in July 2005, and a further flare in May 2007 that shows the highest sub-flare to flare contrast observed until now. The observations can be interpreted in the framework of a model involving a temporary disk with a short jet. In the disk component flux density variations can be explained due to hot spots on relativistic orbits around the central SMBH. The variations of the sub-structures of the May 2007 flare are interpreted as a variation of the hot spot structure due to differential rotation within the disk.

Appeared in: J. of Physics: Conf. Series, V 131, Proc. of ``The Universe Under the Microscope - Astrophysics at High Angular Resolution'', p. 012002 (2008).

Large excess of heavy nitrogen in both hydrogen cyanide and cyanogen from comet 17P/Holmes

D. Bockelée-Morvan$(^{1})$, N. Biver$(^{1})$, E. Jehin$(^{2})$, A.L. Cochran$(^{3})$, H. Wiesemeyer$(^{4})$, J. Manfroid$(^{2})$, D. Hutsemékers$(^{2})$, C. Arpigny$(^{2})$, J. Boissier$(^{5})$, W. Cochran$(^{3})$, P. Colom$(^{1})$, J. Crovisier$(^{1})$, N. Milutinovic$(^{6})$, R. Moreno$(^{1})$, J.X. Prochaska$(^{7})$, I. Ramirez$(^{3})$, R. Schulz$(^{8})$, and J.-M. Zucconi$(^{9})$
$(^{1})$LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92190, Meudon, France, $(^{2})$Institut d'Astrophysique et de Géophysique, Sart-Tilman, B-4000, Liège, Belgium, $(^{3})$Department of Astronomy and McDonald Observatory, University of Texas at Austin, C-1400, Austin, USA, $(^{4})$IRAM, Avenida Divina Pastora, 7, Núcleo Central, E-18012 Granada, Spain, $(^{5})$IRAM, 300 rue de la Piscine, Domaine Universitaire, F-38406, Saint Martin d'Hères, France, $(^{6})$Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria BC V8P 5C2, Canada, $(^{7})$Department of Astronomy and Astrophysics, and UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064, USA, $(^{8})$ESA/RSSD, ESTEC, P.O. Box 299, NL-2200 AG Noordwijk, The Netherlands, $(^{9})$Observatoire de Besançon, F-25010 Besançon Cedex, France

From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of October 24, 2007, we derive $^{14}$N/$^{15}$N=139$\pm$26 in HCN, and $^{14}$N/$^{15}$N=165$\pm$40 in CN, establishing that HCN has the same non-terrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres. The $^{15}$N excess relative to the Earth atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of Solar System formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort-cloud and Kuiper-belt comets. The $^{12}$C/$^{13}$C ratios in HCN and CN are measured to be consistent with the terrestrial value.

Appeared in ApJ 679, L49

Radio observations of Jupiter-family comets

J. Crovisier$(^{1})$, N. Biver$(^{1})$, D. Bockelée-Morvan$(^{1})$, and P. Colom$(^{1})$
$(^{1})$LESIA, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon, France

Radio observations from decimetric to submillimetric wavelengths are now a basic tool for the investigation of comets. Spectroscopic observations allow us i) to monitor the gas production rate of the comets, by directly observing the water molecule, or by observing secondary products (e.g., the OH radical) or minor species (e.g., HCN); ii) to investigate the chemical composition of comets; iii) to probe the physical conditions of cometary atmospheres: kinetic temperature and expansion velocity. Continuum observations probe large-size dust particles and (for the largest objects) cometary nuclei.

Comets are classified from their orbital characteristics into two separate classes: i) nearly-isotropic, mainly long-period comets and ii) ecliptic, short-period comets, the so-called Jupiter-family comets. These two classes apparently come from two different reservoirs, respectively the Oort cloud and the trans-Neptunian scattered disc. Due to their different history and -- possibly -- their different origin, they may have different chemical and physical properties that are worth being investigated.

The present article reviews the contribution of radio observations to our knowledge of the Jupiter-family comets (JFCs). The difficulty of such a study is the commonly low gas and dust productions of these comets. Long-period, nearly-isotropic comets from the Oort cloud are better known from Earth-based observations. On the other hand, Jupiter-family comets are more easily accessed by space missions. However, unique opportunities to observe Jupiter-family comets are offered when these objects come by chance close to the Earth (like 73P/Schwassmann-Wachmann 3 in 2006), or when they exhibit unexpected outbursts (as did 17P/Holmes in 2007).

About a dozen JFCs were successfully observed by radio techniques up to now. Four to ten molecules were detected in five of them. No obvious evidence for different properties between JFCs and other families of comets is found, as far as radio observations are concerned.

Accepted for publication in Planetary & Space Science

Mapping the carbon monoxide coma of comet 29P/Schwassmann-Wachmann 1

M. Gunnarsson$(^{1,2})$, D. Bockelée-Morvan$(^{1})$, N. Biver$(^{1})$, J. Crovisier$(^{1})$, and H. Rickman$(^{2})$
$(^{1})$LESIA, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon, France, $(^{2})$Astronomiska Observatoriet, Box 515, S-75120 Uppsala, Sweden

CO is assumed to be the main driver behind the activity of comet 29P/Schwassmann-Wachmann 1, which resides in a near circular orbit at 6 AU from the Sun. Several properties of the outgassing of CO can be deduced from its millimetre-wave emission. Earlier studies have indicated CO production from the nucleus as well as an extended source. We have sought to further investigate the nature of the CO production in comet 29P/Schwassmann-Wachmann 1, through the use of newly available instrumentation. We used the HERA receiver array on the 30-m IRAM telescope to map the 230 GHz CO($J$=2-1) line in the comet with an unprecedented sensitivity and spatial coverage, and a high spectral resolution (20 kHz, i.e., 25 m s$^{-1}$). A 36-point map, 60 by $60\hbox{$^{\prime\prime}$}$, was obtained in June 2003, and a 25-point map, 96 by $96\hbox{$^{\prime\prime}$}$, in January 2004.

The CO emission line has a characteristic asymmetric profile. Our analysis is based on a coma model, where the outgassing pattern is derived from the shape of this line at the central position of the map. When comparing to the observations, both maps show a line intensity at offset positions which is 2-3 times stronger than the model prediction. Different explanations to this are evaluated, and it is found that for the global coma character, an extremely low gas temperature in the inner coma reproduces the observed radial profile. A cold inner coma depletes the population of the CO $J = 2$ rotational level in the region closest to the nucleus, making spectra observed at offset positions relatively stronger. From the global appearance of the maps, the coma was found to be largely axisymmetric, and the presence of a strong extended source of CO, as indicated from earlier observations using the SEST telescope, was not seen. When examining the maps in more detail, a possible exception to this was seen in an area $30\hbox{$^{\prime\prime}$}$ south of the comet, where an excess in emission is present in both maps. Model fits to the spectra based on the cold inner coma that we find, with an initial kinetic temperature $T_{kin}$ = 4 K, give a measure of $Q_{CO}$, the CO production rate. $Q_{CO}$ was found to be $(3.9\pm0.2) \times 10^{28}$ mol s$^{-1}$ in June 2003, and $(3.7\pm0.2) \times 10^{28}$ mol s$^{-1}$ in January 2004. These values are a factor 1.5 higher than that derived using only the information available from non-mapped data, and this adjustment applies also to previously published production rates.

Appeared in A&A 484, 537

Figure 10: Spectra of the HCO$^+$ absorption toward PKS 1830$-$211 obtained either with the Plateau de Bure Interferometer, or the IRAM 30m telescope, at different epochs between 1995 and 2007. The intensity is normalized with respect to the total (NE+SW) continuum flux. The calibration uncertainties on the PdBI are below 1% Note the strong temporal variations of the -147 kms$^{-1}$ absorption component, which arises in front of the NE image of the quasar, and of the blue wing of the main component, which arises in front of the SW quasar image.

Drastic changes in the molecular absorption at redshift $z=0.89$ toward the quasar PKS 1830$-$211

Muller S. $(^{1})$ - Guélin M. $(^{2,3})$
$(^{1})$Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), P.O. Box 23-141, Taipei, 106, Taiwan, $(^{2})$Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la Piscine, F-38406 St Martin d'Hères, France, $(^{3})$Ecole Normale Supérieure/LERMA, 24 rue Lohmond, F-75005 Paris, France

A 12 year-long monitoring of the absorption caused by a $z=0.89$ spiral galaxy on the line of sight to the radio-loud gravitationally lensed quasar PKS 1830$-$211 reveals spectacular changes in the HCO$^+$ and HCN $(2-1)$ line profiles. The depth of the absorption toward the quasar NE image increased by a factor of $\sim 3$ in 1998-1999 and subsequently decreased by a factor $\geq 6$ between 2003 and 2006 (Fig 10). These changes were echoed by similar variations in the absorption line wings toward the SW image. Most likely, these variations result from a motion of the quasar images with respect to the foreground galaxy, which could be due to a new ejected source component: VLBA observations have shown that the separation between the NE and SW images changed in 1997 by as much as 0.2 mas within a few months. Assuming that motions of similar amplitude occurred in 1999 and 2003, we argue that the clouds responsible for the NE absorption and the broad wings of the SW absorption should be sparse and have characteristic sizes of $0.5-1$ pc.

Appeared in A&A 491, 739

Figure 11: Spectra of IRC +10216, observed with the IRAM 30-m telescope, showing lines from the B1389 series assigned here to C$_5$N$^-$. The marginal weak line U83278 is worth noting, because it is within 0.1 MHz of the J=1-0 line of CCH$^-$.

Detection of C$_5$N$^-$ and vibrationally excited C$_6$H in IRC +10216

J. Cernicharo$(^{1})$, M. Guélin$(^{2})$, M. Agúndez$(^{1})$, M. C. McCarthy$(^{3,4})$ and P. Thaddeus$(^{3,4})$
$(^{1})$DAMIR, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain, $(^{2})$Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Hères, France, $(^{3})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A., $(^{4})$School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, U.S.A.

We report the detection in the envelope of the C-rich star IRC+10216 of four series of lines with harmonically related frequencies: B1389, B1390, B1394 and B1401 (Fig 11). The four series must arise from linear molecules with mass and size close to those of C$_6$H and C$_5$N (Fig. 12). Three of the series have half-integer rotational quantum numbers; we assign them to the $^2\Delta$ and $^2\Sigma^-$ vibronic states of C$_6$H in its lowest ($\nu_{11}$) bending mode. The fourth series, B1389, has integer J with no evidence of fine or hyperfine structure; it has a rotational constant of 1388.860(2) MHz and a centrifugal distortion constant of 33(1) Hz; it is almost certainly C$_5$N$^-$.
C$_5$N$^-$, which has not been observed so far in the laboratory, is the 5th anion detected in interstellar space. Its abundance is found to be fairly high relative to that of its neutral counterpart (between 1/8 and 1/2.)

Appeared in ApJ 688, L83

Figure 12: Model abundances of the neutral radicals C$_n$H, C$_n$N and their anions in the outer envelope of IRC+10216. The abundance of C$_5$N$^-$ is predicted to be high at large radii relative to that of its neutral counterpart, in agreement with the observations.

A Molecular Einstein Ring at $z = 4.12$: Imaging the Dynamics of a Quasar Host Galaxy Through a Cosmic Lens

Dominik A. Riechers $(^{1,2,3})$, Fabian Walter$(^{1})$, Brendon J. Brewer$(^{4})$, Christopher L. Carilli$(^{5})$, Geraint F. Lewis$(^{4})$, Frank Bertoldi$(^{6})$, and Pierre Cox$(^{7})$
$(^{1})$MPIA, Königstuhl 17, Heidelberg, D-69117, Germany, $(^{2})$Astronomy Department, California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125, $(^{3})$Hubble Fellow, $(^{4})$Institute of Astronomy, School of Physics, A28, University of Sydney, NSW 2006, Australia, $(^{5})$NRAO, P.O. Box O, Socorro, NM 87801, $(^{6})$Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, Bonn, D-53121, Germany, $(^{7})$IRAM, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France

We present high-resolution ($0{\farcs3}$) Very Large Array imaging of the molecular gas in the host galaxy of the high-redshift quasar PSS J2322+1944 ($z = 4.12$). These observations confirm that the molecular gas (CO) in the host galaxy of this quasar is lensed into a full Einstein ring and reveal the internal gas dynamics in this system. The ring has a diameter of $\sim 1{\farcs}5$ and thus is sampled over $\sim 20$ resolution elements by our observations. Through a model-based lens inversion, we recover the velocity gradient of the molecular reservoir in the quasar host galaxy of PSS J2322+1944. The Einstein ring lens configuration enables us to zoom in on the emission and to resolve scales down to $\lower.5ex\hbox{$\; \buildrel < \over \sim \;$}1$ kpc. From the model-reconstructed source, we find that the molecular gas is distributed on a scale of 5 kpc and has a total mass of $M(H_2) = 1.7 \times 10^{10} \mbox{M$_\odot$}$. A basic estimate of the dynamical mass gives $M_{dyn} = 4.4\times 10^{10} \sin^{-2}i \mbox{M$_\odot$}$ , that is, only $\sim 2.5$ times the molecular gas mass and $\sim 30$ times the black hole mass (assuming that the dynamical structure is highly inclined). The lens configuration also allows us to tie the optical emission to the molecular gas emission, which suggests that the active galactic nucleus does reside within, but not close to the center of, the molecular reservoir. Together with the (at least partially) disturbed structure of the CO, this suggests that the system is interacting. Such interaction, possibly caused by a major ``wet'' merger, may be responsible for both feeding the quasar and fueling the massive starburst of $680\mbox{M$_\odot$}$ yr$^{-1}$ in this system, in agreement with recently suggested scenarios of quasar activity and galaxy assembly in the early universe.

Appeared in ApJ 686, 851

Thermal emission from warm dust in the most distant quasars

Ran Wang$(^{1,2})$, Chris L. Carilli$(^{2})$, Jeff Wagg$(^{2})$, Frank Bertoldi$(^{3})$, Fabian Walter$(^{4})$, Karl M. Menten$(^{5})$, Alain Omont$(^{6})$, Pierre Cox$(^{7})$, Michael A. Strauss$(^{8})$, Xiaohui Fan$(^{9})$, Linhua Jiang$(^{9})$ and Donald P. Schneider$(^{10})$
$(^{1})$Department of Astronomy, Peking University, Beijing 100871, China, $(^{2})$National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, $(^{3})$Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71,53121 Bonn, Germany, $(^{4})$Max Planck Institute for Astronomy, Königsstuhl 17, 69117 Heidelberg,Germany, $(^{5})$MPIfR, Auf dem Hügel 71, 53121 Bonn,Germany, $(^{6})$Institut d'Astrophysique de Paris, CNRS, and Universite Pierre et MarieCurie, Paris, France, $(^{7})$IRAM, F-38406 St.Martin d'Hères, France, $(^{8})$Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, $(^{9})$Steward Observatory, University of Arizona, Tucson, AZ 85721, $(^{10})$Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802.

We report new continuum observations of 14 $z\sim 6$ quasars at 250 GHz and 14 quasars at 1.4 GHz.We summarize all recent millimeter and radio observations of the sample of the 33 quasars known with $5.71\leq z \leq 6.43$ and present a study of the rest-frame far-infrared (FIR) properties of this sample. These quasars were observed with the Max Planck Millimeter Bolometer Array (MAMBO) at 250 GHz with mJy sensitivity, and 30% of them were detected.We also recover the average 250 GHz flux density of the MAMBO undetected sources at $4 \sigma$ by stacking the on-source measurements. The derived mean radio-to-UV spectral energy distributions (SEDs) of the full sample and the 250 GHz nondetections show no significant differences from lower redshift optical quasars. Obvious FIR excesses are seen in the individual SEDs of the strong 250 GHz detections, with FIR-to-radio emission ratios consistent with those of typical star-forming galaxies. Most 250 GHz- detected sources follow the $L_{FIR}-L_{bol}$ relationship derived from a sample of local IR-luminous quasars ( $L_{IR} > 10^{12} \mbox{L$_\odot$}$), while the average $L_{FIR}/L_{bol}$ ratio of the nondetections is consistent with that of the optically selected PG quasars. The MAMBO detections also tend to have weaker Ly$\alpha$ emission than the nondetected sources.We discuss possible FIR dust-heating sources and critically assess the possibility of active star formation in the host galaxies of the $z\sim 6$ quasars. The average star formation rate of the MAMBO nondetections is likely to be less than a few hundred $\mbox{M$_\odot$}$yr$^{-1}$, but in the strong detections, the host galaxy star formation is probably at a rate of $\lower.5ex\hbox{$\; \buildrel > \over \sim \;$}10^3 \mbox{M$_\odot$}$yr$^{-1}$, which dominates the FIR dust heating.

Appeared in ApJ 687, 848

Interferometric CO observations of submillimeter-faint, radio-selected starburst galaxies at $z\sim 2$

S. C. Chapman$(^{1,2})$, R. Neri$(^{3})$, F. Bertoldi,$(^{4})$, Ian Smail,$(^{5})$, T. R. Greve,$(^{6})$, D. Trethewey,$(^{1})$, A. W. Blain,$(^{7})$, P. Cox,$(^{3})$, R. Genzel,$(^{8})$, R. J. Ivison,$(^{9,10})$, A. Kovacs,$(^{4})$, A. Omont,$(^{11})$ and A. M. Swinbank$(^{5})$
$(^{1})$Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK, $(^{2})$University of Victoria, Victoria, BC, V8W 3P6, Canada, $(^{3})$IRAM, St. Martin d'Hères, France, $(^{4})$MPIfR, Bonn, Germany, $(^{5})$Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE, UK, $(^{6})$Astronomy Department, MPIA, Königsstuhl 17, D-69117 Heidelberg, Germany, $(^{7})$California Institute of Technology, Pasadena, CA 91125, $(^{8})$MPE, Garching, Germany, $(^{9})$UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, $(^{10})$Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, $(^{11})$Institut d'Astrophysique de Paris, CNRS, Université de Paris, Paris, France

High-redshift, dust-obscured galaxies, selected to be luminous in the radio but relatively faint at $850\mu$m, appear to represent a different population from the ultraluminous submillimeter-bright population. They may be star-forming galaxies with hotter dust temperatures, or they may have lower far-infrared luminosities and larger contributions from obscured active galactic nuclei (AGNs). Here we present observations of three $z\sim 2$ examples of this population, which we term ``submillimeter-faint radio galaxies'' (SFRGs; RG J163655, RG J131236, and RG J123711) in CO$(3-2)$ using the IRAM Plateau de Bure Interferometer to study their gas and dynamical properties.We estimate the molecular gas mass in each of the three SFRGs ( $8.3\times 10^9$, $<5.6\times 10^9$, and $15.4 \times
10^9\mbox{M$_\odot$}$, respectively) and, in the case of RG J163655, a dynamical mass by measurement of the width of the CO$(3-2)$ line ( $8\times
10^{10} csc^2i \mbox{M$_\odot$}$). While these gas masses are substantial, on average they are 4 times lower than submillimeter-selected galaxies (SMGs). Radio-inferred star formation rates ($\langle$SFR $_{radio}\rangle = 970\mbox{M$_\odot$}$ yr$^{-1}$) suggest much higher star formation efficiencies than are found forSMGs and shorter gas depletion timescales ($\sim 11$ Myr), much shorter than the time required to form their current stellar masses ($\sim 160$ Myr; $\sim
10^{11} \mbox{M$_\odot$}$ ). By contrast, star formation rates (SFRs) may be overestimated by factors of a few, bringing the efficiencies in line with those typically measured for other ultraluminous star-forming galaxies and suggesting that SFRGs are more like ultraviolet-selected (UV-selected) star-forming galaxies with enhanced radio emission. A tentative detection of RG J163655 at $350 \mu$m suggests hotter dust temperatures, and thus gas-to-dust mass fractions, similar to the SMGs.

Appeared in ApJ 689, 889

A sensitive search for [N II]$_{205\mu m}$ emission in a $z=6.4$ quasar host galaxy

Fabian Walter$(^{1})$, Axel Weiss$(^{2})$, Dominik A. Riechers$(^{3,7})$, Christopher L. Carilli$(^{4})$, Frank Bertoldi$(^{5})$, Pierre Cox$(^{6})$, and Karl M. Menten$(^{2})$
$(^{1})$MPIA, Königstuhl 17, Heidelberg, D-69117, Germany, $(^{2})$MPIfR, Auf dem Hügel 69, Bonn, D-53121, Germany, $(^{3})$Astronomy Department, California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125, USA, $(^{4})$NRAO, P.O. Box O, Socorro, NM 87801, USA, $(^{5})$Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, Bonn, D-53121, Germany, $(^{6})$IRAM, 300 Rue de la Piscine, Domaine Universitaire, F-38406 Saint Martin d'Hères, France

We present a sensitive search for the ${^3P_1} \rightarrow {^3P_0}$ ground-state fine structure line at $205\mu$m of ionized nitrogen ([N II]$_{205\mu m}$) in one of the highest-redshift quasars (J1148+5251 at $z = 6.42$) using the IRAM 30 m telescope. The line is not detected at a ($3\sigma$) depth of 0.47 Jy km s$^{-1}$, corresponding to a [N II]$_{205\mu m}$ luminosity limit of $L_{[N II]} < 4.0\times10^8
\mbox{L$_\odot$}$ and a $L_{[N ii]}/L_{FIR}$ ratio of $< 2\times 10^{-5}$. In parallel, we have observed the CO ($J = 6-5$) line in J1148+5251, which is detected at a flux level consistent with earlier interferometric observations. Using our earlier measurements of the [C II] $158\mu$m line strength, we derive an upper limit for the [N II]$_{205\mu m}$/[C II] line luminosity ratio of $\sim 1/10$ in J1148+5251. Our upper limit for the [C II]/[N II]$_{205\mu m}$ ratio is similar to the value found for our Galaxy and M82 (the only extragalactic system where the [N II]$_{205\mu m}$ line has been detected to date). Given the nondetection of the [N II]$_{205\mu m}$ line we can only speculate whether or not high-z detections are within reach of currently operating observatories. However, [N II]$_{205\mu m}$ and other fine-structure lines will play a critical role in characterizing the interstellarmedium at the highest redshifts ($z > 7$) using the Atacama Large Millimeter/submillimeter Array, for which the highly excited rotational transitions of CO will be shifted outside the accessible (sub-)millimeter bands.

Appeared in ApJ 691, L1

The CO line SED and atomic carbon in IRAS F10214+4724

Y. Ao$(^{1,2})$, A. Weiss$(^{2})$, D. Downes$(^{3})$, F. Walter$(^{4})$, C. Henkel$(^{2})$, and K. M. Menten$(^{2})$
$(^{1})$Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China, $(^{2})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{3})$IRAM, Domaine Universitaire, 38406 St-Martin-d'Hères, France, $(^{4})$MPIA, Königstuhl 17, 69117 Heidelberg, Germany

Using the IRAM 30 m telescope and the Plateau de Bure interferometer we have detected the C I( ${^3P_2} \rightarrow {^3P_1}$) and the CO $3-2$, $4-3$, $6-5$, $7-6$ transitions as well as the dust continuum at 3 and 1.2 mm towards the distant luminous infrared galaxy IRAS F10214+4724 at $z = 2.286$. The C I( ${^3P_2} \rightarrow {^3P_1}$) line is detected for the first time towards this source and IRAS F10214+4724 now belongs to a sample of only 3 extragalactic sources at any redshift where both of the carbon fine structure lines have been detected. The source is spatially resolved by our C I( ${^3P_2} \rightarrow {^3P_1}$) observation and we detect a velocity gradient along the east-west direction. The CI line ratio allows us to derive a carbon excitation temperature of $42^{+12}_{-9}$ K. The carbon excitation in conjunction with the CO ladder and the dust continuum constrain the gas density to $n(H_2) = 10^{3.6-4.0}$ cm$^{-3}$ and the kinetic temperature to $T_{kin} = 45-80$ K, similar to the excitation conditions found in nearby starburst galaxies. The rest-frame $360\mu$m dust continuum morphology is more compact than the line emitting region, which supports previous findings that the far infrared luminosity arises from regions closer to the active galactic nucleus at the center of this system.

Appeared in A&A 491, 747

GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

Racusin J.L.$(^{1})$, and 92 international co-authors
$(^{1})$Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802, USA

Long-duration $\gamma-$ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and $\gamma-$ray emission of GRB080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet.

Appeared in Nature 455, 183

Flares from a candidate Galactic magnetar suggest a missing link to dim isolated neutron stars

Castro-Tirado A.J.$(^{1})$ and 41 international co-authors
$(^{1})$Instituto de Astrofísica de Andalucía del Consejo Superior de Investigaciones Científicas (IAA-CSIC), PO Box 03004, E-18080 Granada, Spain

Magnetars are young neutron stars with very strong magnetic fields of the order of $10^{14}-10^{15}$G. They are detected in our Galaxy either as soft $\gamma$-ray repeaters or anomalous X-ray pulsars. Soft $\gamma$-ray repeaters are a rare type of $\gamma$-ray transient sources that are occasionally detected as bursters in the high-energy sky. No optical counterpart to the $\gamma$-ray flares or the quiescent source has yet been identified. Here we report multi-wavelength observations of a puzzling source, SWIFT J195509+261406. We detected more than 40 flaring episodes in the optical band over a time span of three days, and a faint infrared flare 11 days later, after which the source returned to quiescence. Our radio observations confirm a Galactic nature and establish a lower distance limit of $\sim 3.7$kpc. We suggest that SWIFT J195509+261406 could be an isolated magnetar whose bursting activity has been detected at optical wavelengths, and for which the long-term X-ray emission is short-lived. In this case, a new manifestation of magnetar activity has been recorded and we can consider SWIFT J195509+261406 to be a link between the `persistent' soft $\gamma$-ray repeaters/anomalous X-ray pulsars and dim isolated neutron stars.

Appeared in Nature 455, 506

A photometric redshift of $z = 1.8^{+0.4}_{-0.3}$ for the AGILE GRB 080514B

Rossi, A.$(^{1})$ and 30 international co-authors
$(^{1})$Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany

The AGILE gamma-ray burst GRB 080514B is the first detected to have emission above 30 MeV and an optical afterglow. However, no spectroscopic redshift for this burst is known. We report on our ground-based optical/NIR and millimeter follow-up observations of this event at several observatories, including the multi-channel imager GROND on La Silla, supplemented by Swift UVOT and Swift XRT data. The spectral energy distribution (SED) of the optical/NIR afterglow is found to decline sharply bluewards to the UV bands, which can be utilized in estimating the redshift. Fitting the SED from the Swift UVOT uvw2 band to the H band, we estimate a photometric redshift of $z = 1.8^{+0.4}_{-0.3}$, which is consistent with the reported pseudo-redshift based on gamma-ray data. We find that the afterglow properties of GRB 080514B do not differ from those exhibited by the global sample of long bursts. Compared with the long burst sample, we conclude that this burst was special because of its high-energy emission properties, even though both its afterglow and host galaxy are not remarkable in any way. Obviously, high-energy emission in the gamma-ray band does not automatically correlate with the occurrence of special features in the corresponding afterglow light.

Appeared in A&A 491, L29

Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71
III. Rapid and correlated flux density variability from radio to sub-mm bands

L. Fuhrmann$(^{1,2,3})$, T. P. Krichbaum$(^{1})$, A. Witzel$(^{1})$, A. Kraus$(^{1})$, S. Britzen$(^{1})$, S. Bernhart$(^{1})$, C. M. V. Impellizzeri$(^{1})$, I. Agudo$(^{1,4})$, J. Klare$(^{1})$, B. W. Sohn$(^{1,5})$, E. Angelakis$(^{1})$, U. Bach$(^{1,3})$, K. É. Gabányi$(^{1,6,7})$, E. Körding$(^{8})$, A. Pagels$(^{1})$, J. A. Zensus$(^{1})$, S. J. Wagner$(^{9})$, L. Ostorero$(^{10,11})$, H. Ungerechts$(^{12})$, M. Grewing$(^{13})$, M. Tornikoski$(^{14})$, A. J. Apponi$(^{15})$, B. Vila-Vilaró$(^{16})$, L. M. Ziurys$(^{15})$, and R. G. Strom$(^{17})$
$(^{1})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{2})$Dipartimento di Fisica, Università di Perugia, via A. Pascoli, 06123 Perugia, Italy, $(^{3})$INAF - Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (TO), Italy, $(^{4})$Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain, $(^{5})$Korea Astronomy & Space Science Institute, 61-1 Hwaam-dong, 305-348 Daejeon, Korea, $(^{6})$Hungarian Academy of Sciences Research Group for Physical Geodesy and Geodynamics, Budapest, Hungary, $(^{7})$FÖMI Satellite Geodetic Observatory, Budapest, Hungary, $(^{8})$School of Physics & Astronomy, University of Southampton, Southampton, Hampshire SO17 1BJ, UK, $(^{9})$Landessternwarte Heidelberg-Königstuhl, Königstuhl, 69117 Heidelberg, Germany, $(^{10})$Dipartimento di Fisica Generale ``Amedeo Avogadro'', Università degli Studi di Torino, via P. Giuria 1, 10125 Torino, Italy, $(^{11})$Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy, $(^{12})$IRAM, Avenida Divina Pastora 7, Local 20, 18012 Granada, Spain, $(^{13})$IRAM, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406 Saint-Martin d'Hères, France, $(^{14})$Metsähovi Radio Observatory, Helsinki University of Technology, Metsähovintie 114, 02540 Kylmälä, Finland, $(^{15})$Arizona Radio Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA, $(^{16})$University of Arizona, Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA, $(^{17})$ASTRON, Postbus 2, 7990 AA Dwingeloo; and Astronomical Institute, University of Amsterdam, The Netherlands

Aims. The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC) catastrophe during the states of extreme apparent brightness temperatures.
Methods. The observing campaign involved simultaneous ground-based monitoring at radio to IR/optical wavelengths and was centered around a 500-ks pointing with the INTEGRAL satellite (November 10-17, 2003). Here, we present the combined analysis and results of the radio observations, covering the cm- to sub-mm bands. This facilitates a detailed study of the variability characteristics of an inter- to intra-day variable IDV source from cm- to the short mm-bands. We further aim to constrain the variability brightness temperatures (TB) and Doppler factors ($\delta$) comparing the radio-bands with the hard X-ray emission, as seen by INTEGRAL at 3-200 keV.
Results. 0716+714 was in an exceptionally high state and different (slower) phase of short-term variability, when compared to the past, most likely due to a pronounced outburst shortly before the campaign. The flux density variability in the cm- to mm-bands is dominated by a $\sim 4$ day time scale amplitude increase of up to $\sim 35$%, systematically more pronounced towards shorter wavelengths. The cross-correlation analysis reveals systematic time-lags with the higher frequencies varying earlier, similar to canonical variability on longer time-scales. The increase of the variability amplitudes with frequency contradicts expectations from standard interstellar scintillation (ISS) and suggests a source-intrinsic origin for the observed inter-day variability. We find an inverted synchrotron spectrum peaking near 90 GHz, with the peak flux increasing during the first 4 days. The lower limits to TB derived from the inter-day variations exceed the 1012 K IC-limit by up to 3-4 orders of magnitude. Assuming relativistic boosting, our different estimates of $\delta$ yield robust and self-consistent lower limits of $\delta \geq 5-33$ - in good agreement with $\delta_{VLBI}$ obtained from VLBI studies and the IC-Doppler factors $\delta_{IC} > 14- 16$ obtained from the INTEGRAL data.
Conclusions. The non-detection of S5 0716+714 with INTEGRAL in this campaign excludes an excessively high X-ray flux associated with a simultaneous IC catastrophe. Since a strong contribution from ISS can be excluded, we conclude that relativistic Doppler boosting naturally explains the apparent violation of the theoretical limits. All derived Doppler factors are internally consistent, agree with the results from different observations and can be explained within the framework of standard synchrotron-self-Compton (SSC) jet models of AGN.

Appeared in A&A 490, 1019

Cavities in inner disks: the GM Aurigae case

A. Dutrey$(^{1})$, S. Guilloteau$(^{1})$, V. Piétu$(^{2})$, E. Chapillon$(^{1,2})$, F.Gueth$(^{2})$, T. Henning$(^{3})$, R. Launhardt$(^{3})$, Y. Pavlyuchenkov$(^{3})$, K. Schreyer$(^{4})$, and D. Semenov$(^{3})$
$(^{1})$LAB, UMR 5804, Observatoire de Bordeaux, 2 rue de l'Observatoire, 33270 Floirac, France, $(^{2})$IRAM, 300 rue de la Piscine, 38400 Saint Martin d'Hères, France, $(^{3})$Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany, $(^{4})$Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2-3, 07745 Jena, Germany

Context. Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU.
Aims. We attempt to find evidence of this inner hole in the gas distribution, using spectroscopy with high angular resolution.
Methods. Using the IRAM array, we obtained high angular resolution ( $\sim 1{\farcs}5$) observations with a high S/N per channel of the ${^{13}}$CO $J = 2-1$ and C$^{18}$O $J = 2-1$ and of the ${^{13}}$CO $J = 1-0$ lines. A standard parametric disk model is used to fit the line data in the Fourier-plane and to derive the CO disk properties. Our measurement is based on a detailed analysis of the spectroscopic profile from the CO disk rotating in Keplerian velocity. The millimeter continuum, tracing the dust, is also analyzed.
Results. We detect an inner cavity of radius $19 \pm 4$ AU at the $4.5\sigma$ level. The hole manifests itself by a lack of emission beyond the (projected) Keplerian speed at the inner radius. We also constrain the temperature gradient in the disk.
Conclusions. Our data reveal the existence of an inner hole in GM Aur gas disk. Its origin remains unclear, but can be linked to planet formation or to a low mass stellar companion orbiting close to the central star ($\sim 5-15$ AU). The frequent finding of inner cavities suggests that either binarity is the most common scenario of star formation in Taurus or that giant planet formation starts early.

Appeared in A&A 490, L15

Chemistry in disks II. Poor molecular content of the AB Aurigae disk

K. Schreyer$(^{1})$, S. Guilloteau$(^{2,3})$, D. Semenov$(^{4})$, A. Bacmann$(^{2,3})$, E. Chapillon$(^{5})$, A. Dutrey$(^{2,3})$, F. Gueth$(^{5})$, T. Henning$(^{4})$, F. Hersant$(^{2,3})$, R. Launhardt$(^{4})$, J. Pety$(^{5})$, and V. Piétu$(^{5})$
$(^{1})$Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2-3, 07745 Jena, Germany, $(^{2})$Université Bordeaux 1, Laboratoire d'Astrophysique de Bordeaux (LAB), France, $(^{3})$CNRS/INSU - UMR 5804, BP 89, 33270 Floirac, France, $(^{4})$MPIA, Königstuhl 17, 69117 Heidelberg, Germany, $(^{5})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

Aims. We study the molecular content and chemistry of a circumstellar disk surrounding the Herbig Ae star AB Aur at (sub-)millimeter wavelengths. Our aim is to reconstruct the chemical history and composition of the AB Aur disk and to compare it with disks around low-mass, cooler T Tauri stars.
Methods. We observe the AB Aur disk with the IRAM Plateau de Bure Interferometer in the C- and D-configurations in rotational lines of CS, HCN, C$_2$H, CH$_3$OH, HCO$^+$, and CO isotopes. Using an iterative minimization technique, observed columns densities and abundances are derived. These values are further compared with results of an advanced chemical model that is based on a steady-state flared disk structure with a vertical temperature gradient, and gas-grain chemical network with surface reactions.
Results. We firmly detect HCO$^+$ in the $1-0$ transition, tentatively detect HCN, and do not detect CS, C$_2$H, and CH$_3$OH. The observed HCO$^+$ and ${^{13}}$CO column densities as well as the upper limits to the column densities of HCN, CS, C$_2$H, and CH$_3$OH are in good agreement with modeling results and those from previous studies.
Conclusions. The AB Aur disk possesses more CO, but is less abundant in other molecular species compared to the DM Tau disk. This is primarily caused by intense UV irradiation from the central Herbig A0 star, which results in a hotter disk where CO freeze out does not occur and thus surface formation of complex CO-bearing molecules might be inhibited.

Appeared in A&A 491, 821

Simultaneous NIR/sub-mm observation of flare emission from Sagittarius A*

A. Eckart$(^{1,2})$, R. Schödel$(^{3})$, M. García-Marín$(^{1})$, G. Witzel$(^{1})$, A. Weiss$(^{2})$, F. K. Baganoff$(^{4})$, M. R. Morris$(^{5})$, T. Bertram$(^{1})$, M. Dovciak$(^{})$6, W. J. Duschl$(^{7,8})$, V. Karas$(^{6})$, S. König$(^{1})$, T. P. Krichbaum$(^{2})$, M. Krips$(^{9,14})$, D. Kunneriath$(^{1,2})$, R.-S. Lu$(^{2,1})$, S. Markoff$(^{10})$, J. Mauerhan$(^{5})$, L.Meyer$(^{5})$, J. Moultaka$(^{11})$, K.Muzic$(^{1})$, F. Najarro$(^{12})$, J.-U. Pott$(^{5,13})$, K. F. Schuster$(^{14})$, L. O. Sjouwerman$(^{15})$, C. Straubmeier$(^{1})$, C. Thum$(^{14})$, S. N. Vogel$(^{16})$, H. Wiesemeyer$(^{17})$, M. Zamaninasab$(^{1,2})$, and J. A. Zensus$(^{2})$
$(^{1})$I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany, $(^{2})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{3})$Instituto de Astrofísica de Andalucía, Camino Bajo de Huétor 50, 18008 Granada, Spain, $(^{4})$Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA, $(^{5})$Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA, $(^{6})$Astronomical Institute, Academy of Sciences, Bocní II, 14131 Prague, Czech Republic, $(^{7})$Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany, $(^{8})$Steward Observatory, The University of Arizona, 933 N. Cherry Ave. Tucson, AZ 85721, USA, $(^{9})$Harvard-Smithsonian Center for Astrophysics, SMA project, 60 Garden Street, MS 78 Cambridge, MA 02138, USA, $(^{10})$Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, The Netherlands, $(^{11})$LATT, Université de Toulouse, CNRS, 14 avenue Édouard Belin, 31400 Toulouse, France, $(^{12})$DAMIR, Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid, Spain, $(^{13})$W.M. Keck Observatory (WMKO), CARA, 65-1120 Mamalahoa Hwy., Kamuela, HI-96743, USA, $(^{14})$IRAM, Domaine Universitaire, 38406 Saint-Martin d'Hères, France, $(^{15})$National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA, $(^{16})$Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA, $(^{17})$IRAM, Avenida Divina Pastora, 7, Núcleo Central, 18012 Granada, Spain

Context. We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission of the Sgr A* counterpart associated with the super-massive ( $4 \times 10^6 \mbox{M$_\odot$}$ ) black hole at the Galactic center.
Aims. We study and model the physical processes giving rise to the variable emission of Sgr A*.
Methods. Our non-relativistic modeling is based on simultaneous observations that have been carried out on 03 June, 2008. We used the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and the LABOCA bolometer at the Atacama Pathfinder Experiment (APEX). We emphasize the importance of a multi-wavelength simultaneous fitting as a tool for imposing adequate constraints on the flare modeling.
Results. The observations reveal strong flare activity in the 0.87 mm (345 GHz) sub-mm domain and in the $3.8 \mu{\rm m}/2.2 \mu
{\rm m}$ NIR. Inspection and modeling of the light curves show that the sub-mm follows the NIR emission with a delay of $1.5 \pm 0.5$ h. We explain the flare emission delay by an adiabatic expansion of the source components. The derived physical quantities that describe the flare emission give a source component expansion speed of $v_{exp}
\sim 0.005$c, source sizes around one Schwarzschild radius with flux densities of a few Janskys, and spectral indices of $\alpha = 0.8$ to 1.8, corresponding to particle spectral indices $\sim 2.6$ to 4.6. At the start of the flare the spectra of these components peak at frequencies of a few THz.
Conclusions. These parameters suggest that the adiabatically expanding source components either have a bulk motion greater than $v_{exp}$ or the expanding material contributes to a corona or disk, confined to the immediate surroundings of Sgr A*.

Appeared in A&A 492, 337

First detection of glycolaldehyde outside the galactic center

M. T. Beltrán$(^{1})$, C. Codella$(^{2})$, S. Viti$(^{3})$, R. Neri$(^{4})$ and R. Cesaroni$(^{5})$
$(^{1})$Universitat de Barcelona, Departament d'Astronomia i Meteorologia, Unitat Associada a CSIC, Martí i Franquès 1, 08028 Barcelona, Catalunya, Spain, $(^{2})$INAF, Istituto di Radioastronomia, Sezione di Firenze, Largo E. Fermi 5, I-50125 Firenze, Italy, $(^{3})$Department of Physics and Astronomy, University College London, Gower Street, London WC1E6BT, UK, $(^{4})$IRAM, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France, $(^{5})$INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life.We report on the detection of glycolaldehyde (CH$_2$OHCHO) toward the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, and 2.9 mm. The CH$_2$OHCHO emission comes from the hottest ($\geq 300$ K) and densest ( $\geq 2 \times 10^8$ cm$^{-3}$) region closest ($\leq 10^4$ AU) to the (proto)stars. The comparison of data with gas-grain chemical models of hot cores suggests for G31.41+0.31 an age of a few $10^5$ yr. We also show that only small amounts of CO need to be processed on grains in order for existing hot core gas-grain chemical models to reproduce the observed column densities of glycolaldehyde, making surface reactions the most feasible route to its formation.

Appeared in ApJ 690, L93

Limits on chemical complexity in diffuse clouds: search for CH$_3$ and HC$_5$N absorption

H. S. Liszt$(^{1})$, J. Pety$(^{2,3})$, and R. Lucas$(^{2})$
$(^{1})$NRAO, 520 Edgemont Road, Charlottesville, VA, 22903-2475, USA. $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{3})$Obs. de Paris, 61 Av. de l'Observatoire, 75014 Paris, France

Context. An unexpectedly complex polyatomic chemistry exists in diffuse clouds, allowing detection of species such as C$_2$H, C$_3$H$_2$, H$_2$CO, and NH$_3$, which have relative abundances that are strikingly similar to those inferred toward the dark cloud TMC-1.
Aims. We probe the limits of complexity of diffuse cloud polyatomic chemistry.
Methods. We used the IRAM Plateau de Bure Interferometer to search for galactic absorption from low-lying $J = 2-1$ rotational transitions of A- and E- CH$_3$OH near 96.740 GHz and used the VLA to search for the $J = 8-7$ transition of HC$_5$N at 21.3 GHz.
Results. Neither CH$_3$OH nor HC$_5$N were detected at column densities well below those of all polyatomics known in diffuse clouds and somewhat below the levels expected from comparison with TMC-1. The HCN/HC$_5$N ratio is at least 3 - 10 times higher in diffuse gas than toward TMC-1.

Appeared in A&A 486, 493

Imaging galactic diffuse gas: bright, turbulent CO surrounding the line of sight to NRAO150

J. Pety$(^{1,2})$, R. Lucas$(^{1})$, and H. S. Liszt$(^{3})$
$(^{1})$IRAM, 300 Rue de la Piscine, 38406 Saint Martin d'Hères, France $(^{2})$Obs. de Paris, 61 Av. de l'Observatoire, 75014 Paris, France, $(^{3})$NRAO, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA

Aims. To understand the environment and extended structure of the host galactic gas whose molecular absorption line chemistry, we previously observed along the microscopic line of sight to the blazar/radiocontinuum source NRAO150 (aka B0355+508).
Methods. We used the IRAM 30 m Telescope and Plateau de Bure Interferometer to make two series of images of the host gas: i) $22{\farcs}5$ resolution single-dish maps of ${^{12}}$CO $J = 1-0$ and $2-1$ emission over a $220\hbox{$^{\prime\prime}$}$ by $220\hbox{$^{\prime\prime}$}$ field; ii) a hybrid (interferometer+ single dish) aperture synthesis mosaic of ${^{12}}$CO $J = 1-0$ emission at $5{\farcs}8$ resolution over a $90\hbox{$^{\prime\prime}$}$-diameter region.
Results. At $22{\farcs}5$ resolution, the CO $J = 1-0$ emission toward NRAO150 is 30 - 100% brighter at some velocities than seen previously with $1^\prime$ resolution, and there are some modest systematic velocity gradients over the $220\hbox{$^{\prime\prime}$}$ field. Of the five CO components seen in the absorption spectra, the weakest ones are absent in emission toward NRAO150 but appear more strongly at the edges of the region mapped in emission. The overall spatial variations in the strongly emitting gas have Poisson statistics with rms fluctuations about equal to the mean emission level in the line wings and much of the line cores. The $J = 2-1/J = 1-0$ line ratios calculated pixel-by-pixel cluster around 0.7. At $6\hbox{$^{\prime\prime}$}$ resolution, disparity between the absorption and emission profiles of the stronger components has been largely ameliorated. The ${^{12}}$CO $J = 1-0$ emission exhibits i) remarkably bright peaks, $T_{mb} = 12-13$ K, even as $4\hbox{$^{\prime\prime}$}$ from NRAO150; ii) smaller relative levels of spatial fluctuation in the line cores, but a very broad range of possible intensities at every velocity; and iii) striking kinematics whereby the monotonic velocity shifts and supersonically broadened lines in $22{\farcs}5$ spectra are decomposed into much stronger velocity gradients and abrupt velocity reversals of intense but narrow, probably subsonic, line cores.
Conclusions. CO components that are observed in absorption at a moderate optical depth (0.5) and are undetected in emission at $1^\prime$ resolution toward NRAO 150 remain undetected at $6\hbox{$^{\prime\prime}$}$ resolution. This implies that they are not a previously-hidden large-scale molecular component revealed in absorption, but they do highlight the robustness of the chemistry into regions where the density and column density are too low to produce much rotational excitation, even in CO. Bright CO lines around NRAO150 most probably reflect the variation of a chemical process, i.e. the C$^+ - $CO conversion. However, the ultimate cause of the variations of this chemical process in such a limited field of view remains uncertain.

Appeared in A&A 489, 217

Disks around CQ Tauri and MWC758: dense PDR or gas dispersal?

E. Chapillon$(^{1,2,3})$, S. Guilloteau$(^{1,2})$, A. Dutrey$(^{1,2})$, and V. Piétu$(^{3})$
$(^{1})$Université Bordeaux 1, Laboratoire d'Astrophysique de Bordeaux (LAB), UMR 5804, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France, $(^{2})$CNRS/INSU - UMR 5804, BP 89, 33270 Floirac, France, $(^{3})$IRAM, 300 rue de la Piscine, 38400 Saint Martin d'Hères, France

Context. The overall properties of disks surrounding intermediate PMS stars (HAe) are not yet well constrained by current observations. The disk inclination, which significantly affects spectral energy distribution modeling, is often unknown.
Aims. We attempted to resolve the disks around CQ Tau and MWC 758 to provide accurate constraints on the disk parameters, in particular the temperature and surface density distribution.
Methods. We report arcsecond resolution observations of dust and CO line emissions with the IRAM array. We also searched for the HCO$^+$ $J = 1-0$ transition. The disk properties are derived using a standard disk model. We use the Meudon PDR code to study the chemistry.
Results. The two disks share some common properties. The mean CO abundance is low despite disk temperatures above the CO condensation temperature. Furthermore, the CO surface density and dust opacity have different radial dependence. The CQ Tau disk appears warmer and perhaps less dense than that of MWC 758. Modeling the chemistry, we find that photodissociation of CO is a viable mechanism to explain its low abundance. The photospheric flux is not sufficient for this: a strong UV excess is required. In CQ Tau, the high temperature is consistent with the expectation for a PDR. The PDR model has difficulty explaining the mild temperatures obtained in MWC 758, for which a low gas-to-dust ratio is preferred. A yet, unexplored alternative could be that, despite currently high gas temperatures CO remains trapped in grains, as the models suggest that large grains can be cold enough to prevent thermal desorption of CO. The low inclination of the CQ Tau disk, $\sim 30^\circ$, challenges previous interpretations given for UX Ori - like luminosity variations of this star.
Conclusions. We conclude that CO cannot be used as a simple tracer of gas-to-dust ratio, the CO abundance being affected by photodissociation and grain growth.

Appeared in A&A 488, 565

Search for cold gas along radio lobes in the cooling core galaxies MS0735.6+7421 and M87

P. Salomé$(^{1})$ and F. Combes$(^{2})$
$(^{1})$IRAM, Domaine Universitaire, 300 rue de la piscine, 38400 St Martin d'Hères, France, $(^{2})$LERMA, Observatoire de Paris, 61 av. de l'Observatoire, 75014 Paris, France

We report CO observations towards MS0735.6+7421 a distant cooling core galaxy, and towards M87, the nearest cooling core in the center of the Virgo cluster. Both galaxies contain radio cavities that are thought to be responsible for the heating that can regulate or stop the cooling of the surrounding gas. In this feedback process, there could still be some gas cooling along filaments, along the borders of the radio cavities. Molecular gas is known to exist in clusters with cooling cores, in long and thin filaments that can be formed behind the rising bubbles inflated by the central AGN. CO emission was searched for at several locations along the radio lobes of those two galaxies, but only upper limits were found. These correspond to cold gas mass limits of a few $10^9 \mbox{M$_\odot$}$ for each pointing in MS0735.6+7421, and a few $10^6 \mbox{M$_\odot$}$ in M87. This non detection means that either the cooling is strongly reduced by the AGN feedback or that the gas is cooling in very localized places like thin filaments, possibly diluted in the large beam for MS0735.6+7421. For M87, the AGN heating appears to have stopped the cooling completely.

Appeared in A&A 489, 101

Observations of the Goldreich-Kylafis effect in star-forming regions with XPOL at the IRAM 30 m telescope

J. Forbrich$(^{1,2})$, H. Wiesemeyer$(^{3})$, C. Thum$(^{4})$, A. Belloche$(^{1})$, and K. M. Menten$(^{1})$
$(^{1})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{2})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 72, Cambridge, MA 02138, USA, $(^{3})$IRAM, Avenida Divina Pastora 7, Local 20, 18012 Granada, Spain, $(^{4})$IRAM, Rue de la Piscine, 38406 Saint Martin d'Hères, France

Context. The Goldreich-Kylafis (GK) effect causes certain molecular line emission to be weakly linearly polarized, e.g., in the presence of a magnetic field. Compared to polarized dust emission, the GK effect potentially yields additional information along the line of sight through its dependence on velocity in the line profile.
Aims. Our goal was to detect polarized molecular line emission toward the DR21(OH), W3OH/H$_2$O, G34.3+0.2, and UYSO 1 dense molecular cloud cores in transitions of rare CO isotopologues and CS. The feasibility of such observations had to be established by studying the influence of polarized sidelobes, e.g., in the presence of extended emission in the surroundings of compact sources.
Methods. The observations were carried out with the IRAM 30 m telescope employing the correlation polarimeter XPOL and using two orthogonally polarized receivers. We produced beam maps to investigate instrumental polarization.
Results. While a polarized signal is found in nearly all transitions toward all sources, its degree of polarization in only one case surpasses the polarization that can be expected from instrumental effects. It is shown that any emission in the polarized sidelobes of the system can produce instrumental polarization, even if the source is unpolarized. Tentative evidence of astronomically polarized line emission with $p_L \lower.5ex\hbox{$\; \buildrel < \over \sim \;$}1.5$% was found in the CS$(2-1)$ line toward G34.3+0.2.

Appeared in A&A 492, 757

A new activity phase of the blazar 3C 454.3. Multifrequency observations by the WEBT and XMM-Newton in 2007-2008

Raiteri C. M.$(^{1})$, Villata M.$(^{1})$, Larionov V.M.$(^{2,3})$, Gurwell M.A.$(^{4})$, Chen W.P.$(^{5})$, Kurtanidze O.M.$(^{6})$, Aller M.F.$(^{7})$, Böttcher M.$(^{8})$, Calcidese P.$(^{9})$, Hroch F.$(^{10})$, Lähteenmäki A.$(^{11})$, Lee C.-U.$(^{12})$, Nilsson K.$(^{13})$, Ohlert J.$(^{14})$, Papadakis I.E.$(^{15,16})$, Agudo I.$(^{17})$, Aller H.D.$(^{7})$, Angelakis E.$(^{18})$, Arkharov A.A.$(^{2})$, Bach U.$(^{18})$, Bachev R.$(^{19,})$ Berdyugin A.$(^{13})$, Buemi C.S.$(^{20})$, Carosati D.$(^{21})$, Charlot P.$(^{22,23})$, Chatzopoulos E.$(^{16})$, Forné E.$(^{24})$, Frasca A.$(^{20})$, Fuhrmann L.$(^{18})$, Gómez J.L.$(^{17})$, Gupta A.C.$(^{25})$; Hagen-Thorn V.A.$(^{2})$, Hsiao W.-S.$(^{5})$, Jordan B.$(^{26})$, Jorstad S.G.$(^{27})$, Konstantinova T.S.$(^{2})$, Kopatskaya E.N.$(^{2})$, Krichbaum T.P.$(^{18})$, Lanteri L.$(^{1})$, Larionova L.V.$(^{2})$, Latev G.$(^{28})$, Le Campion J.-F.$(^{22,23})$, Leto P.$(^{29})$, Lin H.-C.$(^{5})$, Marchili N.$(^{18})$, Marilli E.$(^{20})$, Marscher A.P.$(^{27})$, McBreen B.$(^{30})$, Mihov B.$(^{19})$, Nesci R.$(^{31})$, Nicastro F.$(^{32})$, Nikolashvili M.G.$(^{33})$, Novak R.$(^{34})$, Ovcharov E.$(^{28})$, Pian E.$(^{35})$, Principe D.$(^{8})$, Pursimo T.$(^{36})$, Ragozzine B.$(^{8})$, Ros J.A.$(^{24})$, Sadun A.C.$(^{37})$, Sagar R.$(^{25})$, Semkov E.$(^{19})$, Smart R.L.$(^{1})$, Smith N.$(^{38})$, Strigachev A.$(^{19})$, Takalo L.O.$(^{13})$, Tavani M.$(^{39})$, Tornikoski M.$(^{11})$, Trigilio C.$(^{20})$, Uckert K.$(^{8})$, Umana G.$(^{20})$, Valcheva A.$(^{19})$, Vercellone S.$(^{40})$, Volvach A.$(^{41})$ and Wiesemeyer H.$(^{42})$
$(^{1})$INAF - Osservatorio Astronomico di Torino, Italy, $(^{2})$Astron. Inst., St.-Petersburg State Univ., Russia, $(^{3})$Pulkovo Observatory, St. Petersburg, Russia, $(^{4})$Harvard-Smithsonian Center for Astroph., Cambridge, MA, USA, $(^{5})$Institute of Astronomy, National Central University, Taiwan, $(^{6})$Abastumani Astrophysical Observatory, Georgia, $(^{7})$Department of Astronomy, University of Michigan, MI, USA, $(^{8})$Department of Physics and Astronomy, Ohio Univ., OH, USA, $(^{9})$Osservatorio Astronomico della Regione Autonoma Valle d'Aosta, Italy, $(^{10})$Inst. of Theor. Phys. and Astroph., Masaryk Univ., Czech Republic, $(^{11})$Metsähovi Radio Obs., Helsinki Univ. of Technology, Finland, $(^{12})$Korea Astronomy and Space Science Institute, South Korea, $(^{13})$Tuorla Observatory, Univ. of Turku, Piikkiö, Finland, $(^{14})$Michael Adrian Observatory, Trebur, Germany, $(^{15})$IESL, FORTH, Heraklion, Crete, Greece, $(^{16})$Physics Department, University of Crete, Greece, $(^{17})$Instituto de Astrofíisica de Andalucía (CSIC), Granada, Spain, $(^{18})$MPIfR, Bonn, Germany, $(^{19})$Inst. of Astronomy, Bulgarian Academy of Sciences, Sofia, Bulgaria, $(^{20})$INAF - Osservatorio Astrofisico di Catania, Italy, $(^{21})$Armenzano Astronomical Observatory, Italy, $(^{22})$Université de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, Floirac, France, $(^{23})$CNRS, Laboratoire d'Astrophysique de Bordeaux, UMR 5804, Floirac, France, $(^{24})$Agrupació Astronòmica de Sabadell, Spain, $(^{25})$ARIES, Manora Peak, Nainital, India, $(^{26})$School of Cosmic Physics, Dublin Institute For Advanced Studies, Ireland, $(^{27})$Institute for Astrophysical Research, Boston University, MA, USA, $(^{28})$Sofia University, Bulgaria, $(^{29})$INAF - Istituto di Radioastronomia, Sezione di Noto, Italy, $(^{30})$School of Physics, University College Dublin, Ireland, $(^{31})$Dept. of Phys. ``La Sapienza'' Univ, Roma, Italy, $(^{32})$INAF - Osservatorio Astronomico di Roma, Italy, $(^{33})$Abastumani Astrophysical Observatory, Georgia, $(^{34})$N. Copernicus Observatory and Planetarium in Brno, Czech Republic, $(^{35})$INAF - Osservatorio Astronomico di Trieste, Italy, $(^{36})$Nordic Optical Telescope, Santa Cruz de La Palma, Spain, $(^{37})$Dept. of Phys., Univ. of Colorado Denver, Denver, CO USA, $(^{38})$Cork Institute of Technology, Cork, Ireland, $(^{39})$INAF, IASF-Roma, Italy, $(^{40})$INAF, IASF-Milano, Italy, $(^{41})$Radio Astronomy Lab. of Crimean Astrophysical Observatory, Ukraine, $(^{42})$IRAM Granada, Spain

Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from the radio to the optical bands since 2004 to study its emission variability properties.
Methods. We present and analyse the multifrequency results of the 2007-2008 observing season, including XMM-Newton observations and near-IR spectroscopic monitoring, and compare the recent emission behaviour with the past one. The historical mm light curve is presented here for the first time.
Results. In the optical band we observed a multi-peak outburst in July-August 2007, and other faster events in November 2007-February 2008. During these outburst phases, several episodes of intranight variability were detected. A mm outburst was observed starting from mid-2007, whose rising phase was contemporaneous to the optical brightening. A slower flux increase also affected the higher radio frequencies, the flux enhancement disappearing below 8 GHz. The analysis of the optical-radio correlation and time delays, as well as the behaviour of the mm light curve, confirm our previous predictions, suggesting that changes in the jet orientation likely occurred in the last few years. The historical multiwavelength behaviour indicates that a significant variation in the viewing angle may have happened around year 2000. Colour analysis confirms a general redder-when-brighter trend, which reaches a ``saturation'' at $R \sim 14$ and possibly turns into a bluer-when-brighter trend in bright states. This behaviour is due to the interplay of different emission components, the synchrotron one possibly being characterised by an intrinsically variable spectrum. All the near-IR spectra show a prominent H$\alpha$ emission line ( $EW_{obs} = 50-120$ Å), whose flux appears nearly constant, indicating that the broad line region is not affected by the jet emission. We show the broad-band SEDs corresponding to the epochs of the XMM-Newton pointings and compare them to those obtained at other epochs, when the source was in different brightness states. A double power-law fit to the EPIC spectra including extra absorption suggests that the soft-X-ray spectrum is concave, and that the curvature becomes more pronounced as the flux decreases. This connects fairly well with the UV excess, which becomes more prominent with decreasing flux. The most obvious interpretation implies that, as the beamed synchrotron radiation from the jet dims, we can see both the head and the tail of the big blue bump. The X-ray flux correlates with the optical flux, suggesting that in the inverse-Compton process either the seed photons are synchrotron photons at IR-optical frequencies or the relativistic electrons are those that produce the optical synchrotron emission. The X-ray radiation would thus be produced in the jet region from where the IR-optical emission comes.

Appeared in A&A 491, 755

CN Zeeman measurements in star formation regions

Falgarone E.$(^{1})$, Troland T.H.$(^{2})$, Crutcher R.M.$(^{3})$, Paubert G.$(^{4})$
$(^{1})$LERMA/LRA, CNRS UMR 8112, École Normale Supérieure and Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France, $(^{2})$University of Kentucky, Department of Physics and Astronomy, Lexington, KY 40506, USA, $(^{3})$University of Illinois, Department of Astronomy, Urbana, IL 61801, USA, $(^{4})$IRAM, 7 avenida Divina Pastora, Granada, Spain

Aims. Magnetic fields play a primordial role in the star formation process. The Zeeman effect on the CN radical lines is one of the few methods of measuring magnetic fields in the dense gas of star formation regions.
Methods. We report new observations of the Zeeman effect on seven hyperfine CN $N = 1-0$ lines in the direction of 14 regions of star formation.
Results. We have improved the sensitivity of previous detections, and obtained five new detections. Good upper limits are also achieved. The probability distribution of the line-of-sight field intensity, including non-detections, provides a median value of the total field $B_{tot} = 0.56$ mG while the average density of the medium sampled is $n(H_2) = 4.5 \times 10^5$cm$^{-3}$. We show that the CN line probably samples regions similar to those traced by CS and that the magnetic field observed mostly pervades the dense cores. The dense cores are found to be critical to slightly supercritical with a mean mass-to-flux ratio $M/\Phi \sim 1$ to 4 with respect to critical. Their turbulent and magnetic energies are in approximate equipartition.

Appeared in A&A 487, 247

Monitoring Venus' mesospheric winds in support of Venus Express: IRAM 30-m and APEX observations

Lellouch E.$(^{1})$, Paubert G.$(^{2})$, Moreno R.$(^{1})$, Moullet A.$(^{1})$
$(^{1})$LESIA, Observatoire de Paris, 92195 Meudon Cedex, France, $(^{2})$IRAM, Granada, Spain

We report on direct wind measurements in Venus' mesosphere ($90 -
115$ km), performed in support of Venus Express, and based on CO millimeter observations. Most observations, sampling the CO$(2-1)$ and CO$(1-0)$ lines, were acquired with the IRAM 30-m telescope, over four distinct periods: (i) Summer 2006; (ii) May June 2007, in association with the coordinated ground-based campaign; (iii) August 2007 inferior conjunction and (iv) September 2007. In the latter period, additional measurements (CO$(3-2)$) were obtained with the APEX 12-m telescope. Overall, the measurements indicate a large body of temporal variability of the Venus mesospheric field, but general features emerge: (i) winds strongly increase with altitude within the mesosphere, by a factor of $2-3$ over a decade in pressure; (ii) many, but not all, of our observations can be viewed as the superposition of zonal retrograde and subsolar-to-antisolar (SSAS) flows of comparable speeds, typically $30-50$ m/s near 0.1 mbar ($\sim 93$km) and $90-120$ m/s near 0.01 mbar ($\sim 102$km) (iii) the wind field was very stable over three consecutive observing days in May June 2007, but much more variable on a similar time base in August 2007 (iv) at a $\sim
2000$ km resolution, the nightside wind field appears very complex, with evidence that the SSAS flow does not reach high latitudes, and possible evidence for additional meridional winds. Our Summer 2006 observations, which sample Venus' dayside, seem to suggest that a prograde zonal flow is superimposed to the SSAS circulation for this period. This surprising result, which implies a pre-midnight convergence of the wind field, requires confirmation, and fruitful comparisons may be obtained from the analysis of motions in the O$_2$ emission images, as observed by Venus Express.

Appeared in: Planetary and Space Science 56, 1355

Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007s

V.M. Larionov$(^{1,2})$, S.G. Jorstad$(^{1,21})$, A.P. Marscher$(^{21})$, C.M. Raiteri$(^{3})$, M. Villata$(^{3})$, I. Agudo$(^{4})$, M.F. Aller$(^{5})$, A.A. Arkharov$(^{2})$, I. M. Asfandiyarov$(^{20})$, U. Bach$(^{6})$, R. Bachev$(^{7})$, A. Berdyugin$(^{28})$, M. Böttcher$(^{8})$, C. S. Buemi$(^{16})$, P. Calcidese$(^{9})$, D. Carosati$(^{10})$, P. Charlot$(^{11})$, W.-P. Chen$(^{12})$, A. Di Paola$(^{13})$, M. Dolci$(^{14})$, S. Dogru$(^{15})$, V. T. Doroshenko$(^{34,40,41})$, Yu. S. Efimov$(^{34})$, A. Erdem$(^{15})$, A. Frasca$(^{16})$, L. Fuhrmann$(^{6})$, P. Giommi$(^{36})$, L. Glowienka$(^{17})$, A. C. Gupta$(^{18,44})$, M. A. Gurwell$(^{19})$, V. A. Hagen-Thorn$(^{1})$, W.-S.Hsiao$(^{12})$, M. A. Ibrahimov$(^{20})$, B. Jordan$(^{40})$, M. Kamada$(^{22})$, T. S. Konstantinova$(^{1})$, E. N. Kopatskaya$(^{1})$, Y. Y. Kovalev$(^{6,23})$, Y. A. Kovalev$(^{23})$, O. M. Kurtanidze$(^{24})$, A. Lähteenmäki$(^{25})$, L. Lanteri$(^{3})$, L. V. Larionova$(^{1})$, P. Leto$(^{37})$, P. Le Campion$(^{11})$, C.-U. Lee$(^{26})$, E. Lindfors$(^{28})$, E. Marilli$(^{16})$, I. McHardy$(^{27})$, M. G. Mingaliev$(^{42})$, S. V. Nazarov$(^{34})$, E. Nieppola$(^{25})$, K. Nilsson$(^{28})$, J. Ohlert$(^{29})$, M. Pasanen$(^{28})$, D. Porter$(^{30})$, T. Pursimo$(^{31})$, J. A. Ros$(^{32})$, K. Sadakane$(^{22})$, A. C. Sadun$(^{33})$, S. G. Sergeev$(^{34,41})$, N. Smith$(^{39})$, A. Strigachev$(^{7})$, N. Sumitomo$(^{22})$, L. O. Takalo$(^{28})$, K. Tanaka$(^{22})$, C. Trigilio$(^{16})$, G. Umana$(^{16})$, H. Ungerechts$(^{43})$, A. Volvach$(^{35})$, and W. Yuan$(^{18})$
$(^{1})$Astron. Inst., St.-Petersburg State Univ., Russia, $(^{2})$Pulkovo Observatory, St.-Petersburg, Russia, $(^{3})$INAF, Osservatorio Astronomico di Torino, Italy, $(^{4})$Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain, $(^{5})$Department of Astronomy, University of Michigan, MI, USA, $(^{6})$MPIfR, Bonn, Germany, $(^{7})$Inst. of Astron., Bulgarian Acad. of Sciences, Sofia, Bulgaria, $(^{8})$Department of Physics and Astronomy, Ohio Univ., OH, USA, $(^{9})$Oss. Astronomico della Regione Autonoma Valle d'Aosta, Italy, $(^{10})$Armenzano Astronomical Observatory, Italy, $(^{11})$Lab. d'Astrophys., Univ. Bordeaux 1, CNRS, Floirac, France, $(^{12})$Institute of Astronomy, National Central University, Taiwan, $(^{13})$INAF, Osservatorio Astronomico di Roma, Italy, $(^{14})$INAF, Osservatorio Astronomico di Collurania Teramo, Italy, $(^{15})$COMU Observatory, Turkey, $(^{16})$INAF, Osservatorio Astrofisico di Catania, Italy, $(^{17})$Department of Phys. and Astron. Univ. of Aarhus, Denmark, $(^{18})$YNAO, Chinese Academy of Sciences, Kunming, PR China, $(^{19})$Harvard-Smithsonian Center for Astroph., Cambridge, MA, USA, $(^{20})$Ulugh Beg Astron. Inst., Tashkent, Uzbekistan, $(^{21})$Inst. for Astrophys. Research, Boston Univ., MA, USA, $(^{22})$Astronomical Institute, Osaka Kyoiku University, Japan, $(^{23})$Astro Space Centre of Lebedev Physical Inst., Moscow, Russia, $(^{24})$Abastumani Astrophysical Observatory, Georgia, $(^{25})$Metsähovi Radio Obs., Helsinki Univ. of Technology, Finland, $(^{26})$Korea Astronomy and Space Science Institute, South Korea, $(^{27})$University of Southampton, UK, $(^{28})$Tuorla Observatory, Univ. of Turku, Piikkiö, Finland, $(^{29})$Michael Adrian Observatory, Trebur, Germany, $(^{30})$Cardiff University, Wales, UK, $(^{31})$Nordic Optical Telescope, Santa Cruz de La Palma, Spain, $(^{32})$Agrupació Astronòmica de Sabadell, Spain, $(^{33})$Dept. of Phys., Univ. of Colorado, Denver, USA, $(^{34})$Crimean Astrophysical Observatory, Ukraine, $(^{35})$Radio Astron. Lab. of Crimean Astroph. Observatory, Ukraine, $(^{36})$ASI Science Data Centre, Frascati, Italy, $(^{37})$INAF, Istituto di Radioastronomia, Sezione di Noto, Italy, $(^{38})$School of Cosmic Physics, Dublin Inst. for Adv. Studies, Ireland, $(^{39})$Cork Institute of Technology, Cork, Ireland, $(^{40})$Moscow Univ., Crimean Lab. of Sternberg Astron. Inst., Ukraine, $(^{41})$Isaac Newton Institute of Chile, Crimean Branch, Ukraine, $(^{42})$Special Astrophysical Observatory, N. Arkhyz, Russia, $(^{43})$IRAM Granada, Spain, $(^{44})$ARIES, Manora Peak, Nainital, India

Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability of flux at all wavebands. Its variations in flux and polarization are quite complex and therefore require intensive monitoring observations at multiple wavebands to characterise and interpret the observed changes.
Aims. In this paper, we present radio-to-optical data taken by the WEBT, supplemented by our VLBA and RXTE observations, of 3C 279. Our goal is to use this extensive database to draw inferences regarding the physics of the relativistic jet. Methods. We assemble multifrequency light curves with data from 30 ground-based observatories and the space-based instruments SWIFT (UVOT) and RXTE, along with linear polarization vs. time in the optical R band. In addition, we present a sequence of 22 images (with polarization vectors) at 43 GHz at resolution 0.15 milliarcsec, obtained with the VLBA. We analyse the light curves and polarization, as well as the spectral energy distributions at different epochs, corresponding to different brightness states.
Results. We find that the IR-optical-UV continuum spectrum of the variable component corresponds to a power law with a constant slope of $-1.6$, while in the $2.4-10$ keV X-ray band it varies in slope from $-1.1$ to $-1.6$. The steepest X-ray spectrum occurs at a flux minimum. During a decline in flux from maximum in late 2006, the optical and 43 GHz core polarization vectors rotate by $\sim 300^\circ$.
Conclusions. The continuum spectrum agrees with steady injection of relativistic electrons with a power-law energy distribution of slope $-3.2$ that is steepened to $-4.2$ at high energies by radiative losses. The X-ray emission at flux minimum comes most likely from a new component that starts in an upstream section of the jet where inverse Compton scattering of seed photons from outside the jet is important. The rotation of the polarization vector implies that the jet contains a helical magnetic field that extends $\sim 20$ pc past the 43 GHz core.

Appeared in A&A 492, 389

Instrument performance of GISMO, a 2 millimeter TES bolometer camera used at the IRAM 30 m Telescope

Staguhn Johannes G.$(^{1,2})$, Benford Dominic J.$(^{1})$, Allen Christine A.$(^{1})$, Maher Stephen F.$(^{1,3})$, Sharp Elmer H.$(^{1,4})$, Ames Troy J.$(^{1})$, Arendt Richard G.$(^{1,5})$, Chuss David T.$(^{1})$, Dwek Eli$(^{1,2})$, Fixsen Dale J.$(^{1})$, Miller Tim M.$(^{1,6})$, Moseley S. Harvey$(^{1})$, Navarro Santiago$(^{7})$, Sievers Albrecht$(^{7})$ and Wollack Edward J.$(^{1})$
$(^{1})$NASA Goddard Space Flight Ctr., USA, $(^{2})$Univ. of Maryland, College Park, USA, $(^{3})$Science Systems & Applications, USA, $(^{4})$Global Science & Technology, USA, $(^{5})$Univ. of Maryland Baltimore County, USA, $(^{6})$MEI Technologies, USA, $(^{7})$IRAM Granada, Spain

We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for infrared through millimeter wavelengths. Our latest array architecture is based on our Backshort Under Grid (BUG) design, which is specifically targeted at producing kilopixel-size arrays for future ground-based, suborbital and space-based X-ray and far-infrared through millimeter cameras and spectrometers. In November of 2007, we demonstrated a monolithic $8\times16$ BUG bolometer array with 2 mm-pitch detectors for astronomical observations using our 2 mm wavelength camera GISMO (the Goddard IRAM Superconducting 2 Millimeter Observer) at the IRAM 30m telescope in Spain. The 2 mm spectral range provides a unique terrestrial window enabling ground-based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We present preliminary results from our observing run with the first fielded BUG bolometer array and discuss the performance of the instrument.

Appeared in: Mm and Sub-mm Detectors and Instrumentation for Astronomy IV. Eds Duncan, Holland, Withington, Jonas, Proc. of the SPIE Vol. 7020, 702004

Extrasolar planet detection by binary stellar eclipse timing: evidence for a third body around CM Draconis

H. J. Deeg$(^{1})$, B. Ocaña$(^{1,2})$, V. P. Kozhevnikov$(^{3})$, D. Charbonneau$(^{4})$, F. T. O'Donovan$(^{5})$, and L. R. Doyle$(^{6})$
$(^{1})$Instituto de Astrofísica de Canarias, C. Via Lactea S/N, 38205 La Laguna, Tenerife, Spain, $(^{2})$IRAM, Av. Divina Pastora 7, Núcleo Central, 18012 Granada, Spain, $(^{3})$Astronomical Observatory, Ural State University, Lenin ave. 51, Ekaterinburg, 620083, Russia, $(^{4})$Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA, $(^{5})$California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA, $(^{6})$SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA

Aims. Our objective is to elucidate the physical process that causes the observed observed-minus-calculated (O-C) behavior in the M4.5/M4.5 binary CM Dra and to test for any evidence of a third body around the CM Dra system.
Methods. New eclipse minimum timings of CM Dra were obtained between the years 2000 and 2007. The O-C times of the system are fitted against several functions, representing different physical origins of the timing variations.
Results. Using our observational data in conjunction with published timings going back to 1977, a clear non-linearity in O-C times is apparent. An analysis using model-selection statistics gives about equal weight to a parabolic and to a sinusoidal fitting function. Attraction from a third body, either at large distance in a quasi-constant constellation across the years of observations or from a body on a shorter orbit generating periodicities in O-C times is the most likely source of the observed O-C times. The white dwarf GJ 630.1B, a proper motion companion of CM Dra, can however be rejected as the responsible third body. Also, no further evidence of the shortperiodic planet candidate described by Deeg et al. (2000, A&A, 358, L5) is found, whereas other mechanisms, such as period changes from stellar winds or Applegate's mechanism can be rejected.
Conclusions. A third body, being either a few-Jupiter-mass object with a period of $18.5 \pm 4.5$ years or an object in the mass range of $1.5 M_{jup}$ to $0.1 \mbox{M$_\odot$}$ with periods of hundreds to thousands of years is the most likely origin of the observed minimum timing behavior.

Appeared in A&A 480, 563

The brightness temperature of Mercury at mm-wavelengths

A. Greve$(^{1})$, C. Thum$(^{1})$, R. Moreno$(^{1,2})$ and N. Yan$(^{3})$
$(^{1})$IRAM, 300 rue de la Piscine, 38406 St. Martin d`Hères, France, $(^{2})$LESIA (LAM -bat. 18), 5 Place Jules Janssen, 92195 Meudon Cedex, France, $(^{3})$Service d'Aeronomie CNRS/IPSL, 91371 Verrieres-le-Buisson, France

We present observations of Mercury made with the IRAM 30-m telescope at 3,2 and 1.3mm wavelength (90,150 and 230 GHz) during the years 1985 - 2005; we derive from these data the disk-averaged brightness temperatures. The observations at 3mm combined with those by Epstein $\&$ Andrew allow a separation of the data into 40$\degr$ wide longitude intervals and by this an investigation of the disk-averaged brightness temperature with Mercury's longitude. From the new mm-wavelength data, and data taken from the literature, we derive the disk-averaged brightness temperature as a function of wavelength. On Mercury's night side a significant decrease in brightness temperature occurs towards shorter wavelengths.
We use the three surface models (A,B,C) discussed by Mitchell & de Pater and calculate for the cool and hot surface region the corrresponding diurnal variation of the disk-averaged brightness temperature at 90GHz. For the same models we calculate the variation of the disk-averaged brightness temperature with wavelength between 1.3mm and 37mm, on Mercury's midnight side and noon side. Although the scatter in the observations is large, there seems to be a marginally better agreement with model B and A.

A&A, in print

Surface adjustment of the IRAM 30 m radio telescope

D. Morris$(^{1,2})$, M. Bremer$(^{1})$, G. Butin$(^{1})$, M. Carter$(^{1})$, A. Greve$(^{1})$, J.W. Lamb$(^{1,3})$, B. Lazareff$(^{1})$, J. Lopez-Perez$(^{1,4})$, F. Mattiocco$(^{1})$, J. Peñalver$(^{1})$ and C. Thum$(^{1})$
$(^{1})$IRAM, St Martin d'Hères, France, $(^{2})$Raman Research Institute, Bangalore, India, $(^{3})$California Institute of Technology, OVRO, Big Pine, USA, $(^{4})$OAN, Centro Astronomico de Yebes, Guadalajara, Spain

The techniques used to set and stabilise the surface of the IRAM 30 m radio telescope to a final root mean square accuracy of about 50 $\mu$m are described. This involved both phase retrieval and phase coherent holography using a variety of radiation sources at several frequencies. A finite-element model was utilised in improving the temperature control system for the telescope structure. The factors influencing the ultimate surface accuracy are discussed.

Appeared in: IET Microwaves, Antennas & Propagation, Feb. 2009, Vol.3, Issue 1, 99

A kiloparsec-scale hyper-starburst in a quasar host less than 1 gigayear after the Big Bang

F.Walter$(^{1})$, D.Riechers$(^{1})$, P.Cox$(^{2})$, R.Neri$(^{2})$, C.Carilli$(^{3})$, F.Bertoldi$(^{4})$, A.Weiss$(^{5})$ and R.Maiolino$(^{6})$
$(^{1})$Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany, $(^{2})$IRAM, 300 rue de la Piscine, F-38406 St-Martin-d'Hères, France, $(^{3})$NRAO, PO Box O, Socorro, New Mexico 87801, USA, $(^{4})$Argelander Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany, $(^{5})$MPIfR, Auf dem Hügel 69, D-53121 Bonn, Germany, $(^{6})$L'Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone, Roma, Italy

The host galaxy of the quasar SDSS J114816.64+525150.3 (at redshift $z = 6.42$, when the Universe was less than a billion years old) has an infrared luminosity of $2.2\times10^{13}$ times that of the Sun, presumably significantly powered by a massive burst of star formation. In local examples of extremely luminous galaxies, such as Arp 220, the burst of star formation is concentrated in a relatively small central region of $<100$ pc radius. It is not known on which scales stars are forming in active galaxies in the early Universe, at a time when they are probably undergoing their initial burst of star formation. We do know that at some early time, structures comparable to the spheroidal bulge of the Milky Way must have formed. Here we report a spatially resolved image of [CII] emission of the host galaxy of J114816.64+525150.3 that demonstrates that its star-forming gas is distributed over a radius of about 750 pc around the centre. The surface density of the star formation rate averaged over this region is $\sim 1,000$year$^{-1}$kpc$^{-2}$. This surface density is comparable to the peak in Arp 220, although about two orders of magnitude larger in area. This vigorous star-forming event is likely to give rise to a massive spheroidal component in this system.

Appeared in: Nature 457, 699

A complete $^{12}$CO 2-1 map of M51 with HERA: II. Total gas surface densities and gravitational stability

M. Hitschfeld$(^{1})$, C. Kramer$(^{1,2})$, K.F. Schuster$(^{3})$, S. Garcia-Burillo$(^{4})$, J. Stutzki$(^{1})$
$(^{1})$KOSMA, I. Physikalisches Institut, Universität zu Köln, Germany, $(^{2})$IRAM Granada, Spain, $(^{3})$IRAM Grenoble, France, $(^{4})$Observatorio de Madrid, Spain

To date the onset of large-scale star formation in galaxies and its link to gravitational stability of the galactic disk have not been fully understood. The nearby face-on spiral galaxy M51 is an ideal target for studying this subject. This paper combines CO, dust, HI, and stellar maps of M51 and its companion galaxy to study the H$_2$/HI transition, the gas-to-dust ratios, and the stability of the disk against gravitational collapse.

We combine maps of the molecular gas using $^{12}$CO 2-1 map HERA/IRAM-30m data and HI VLA data to study the total gas surface density and the phase transition of atomic to molecular gas. The total gas surface density is compared to the dust surface density from $850{\mu}$m SCUBA data. Taking into account the velocity dispersions of the molecular and atomic gas, and the stellar surface densities derived from the 2MASS K-band survey, we derive the total Toomre Q parameter of the disk.

The gas surface density in the spiral arms is $\sim 2-3$ higher compared to that of the interarm regions. The ratio of molecular to atomic surface density shows a nearly power-law dependence on the hydrostatic pressure $P_{hydro}$. The gas surface density distribution in M51 shows an underlying exponential distribution with a scale length of $h_{gas}=7.6$ kpc representing 55% of the total gas mass, comparable to the properties of the exponential dust disk. In contrast to the velocity widths observed in HI, the CO velocity dispersion shows enhanced line widths in the spiral arms compared to the interarm regions. The contribution of the stellar component in the Toomre Q-parameter analysis is significant and lowers the combined Q-parameter Q$_{tot}$ by up to 70% towards the threshold for gravitational instability. The value of Q$_{tot}$ varies from $1.5-3$ in radial averages. A map of Q$_{tot}$ shows values around 1 on the spiral arms indicating self-regulation at play.

Accepted for publication in A&A

next up previous
Next: IRAM Astronomy Postdoctoral Position Up: IRAM Newsletter 72 (February 2009) Previous: Matt Carter in memoriam