Scientific Highlights Archive

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This archive contains reports on scientific results from the IRAM observatories, which had been previously published on our "Recent Results" page. If you are interested in discoveries which have recently been made available to IRAM by the authors, please clic here.

PR 1011/05
IRAM PR 1011/05

A disk of dust and water around a young high-mass star    F.F.S. van der Tak, C.M. Walmsley, F. Herpin, C. Ceccarelli Max-Planck-Institut für Radioastronomie, Bonn, Germany

High-mass stars may form by disk accretion like low-mass stars, but observational evidence for massive circumstellar disks remains sparse, even after intense searches. New observations with the IRAM Plateau de Bure interferometer of dust continuum (strong source in the upper left diagram, the two weak sources are dominated by free-free emission) and H218O line emission (upper right diagram) at 1.3 mm wavelength show a rotating disk around the nearby (distance = 1kpc) high-mass (20,000 solar luminosity) protostar AFGL 2591, whose infrared K-band image (Preibisch et al. 2003 (A&A 412, 735)) is shown in the lower left.

The mass of the disk is 0.8 solar masses, or 5% of the mass of the central star. The observations show that the dust grains in the disk are unusually large, as a result of coagulation. The disk is seen in an almost face-on orientation. The spectral line data show rotating motions, and the rotation speed is as expected for a star of this mass. The diagram on the lower right displays, in each velocity channel, the offset of the H218O emission peak from the phase center. Triangles indicate redshifted material, circles correspond to the line center, and squares mark blueshifted gas. The disk is very rich in water, because the ice mantles on the dust grains have recently evaporated.

For more details see astro-ph/0510640 (A&A in press)

PR 1005/05
IRAM PR 1005/05

Continuum emission in NGC1068:  Indications for a turnover in the core spectrum    M. Krips, A. Eckart, R. Neri, R. Schödel, S. Leon, D. Downes, S. García-Burillo, F. Combes Harvard-Smithsonian Center for Astrophysics, SMA, Hawaii

The bright, nearby (D=14Mpc) active galaxy NGC1068 is regarded to be the archetype for unification schemes of Seyferts based on the directional obscuration of its AGN. High angular resolution observations were recently carried out at 3mm and 1mm with the IRAM PdBI using its A configuration. Three continuum peaks are detected in NGC1068, one centered on the core, one associated with the jet and a third one with the counter-jet.

This is the first significant detection of the large scale radio jet and counter-jet at mm wavelengths in NGC1068. The central emission peak located at the position of the radio core also contains a significant fraction (~60%) of different jet components detected within the central 2'' in higher angular resolution radio maps (e.g., Gallimore et al. 2004). While the fluxes of the (large scale) jet components agree with a steep spectral index extrapolated from cm-wavelengths, the core fluxes indicate a turnover of the inverted cm- into a steep mm-spectrum at roughly 50GHz which is most likely caused by electron-scattered synchrotron emission (ESSE) in the obscured central region of NGC1068.

For more details, see astro-ph/0509825 (A&A in press)

PR 0128/05
IRAM PR 0128/05

Molecular gas observation of a triply lensed galaxy typical of the Cosmic Far-Infrared Background    J-P. Kneib, R. Neri, I. Smail, A. Blain, K. Sheth, P. van der Werf, K. Knudsen OAMP, Laboratoire d'Astronomie de Marseille, France

The submm galaxy SMMJ16359+6612 at z~2.5 is strongly lensed by the massive cluster Abell 2218. The lens produces three images of this intrinsically faint (~0.8mJy at 850um) galaxy. The large total magnification factor of 45 provides a rare opportunity to probe in detail the nature of a distant galaxy, part of the population which produces the bulk of the submm cosmic far-infrared background.

Sensitive D-configuration observations have been made with the Plateau de Bure interferometer to map in detail the CO(3-2) emission line. The data show an outstanding double-peak velocity profile. By constraining these observations with Hubble Space Telescope imaging and Keck infrared spectroscopy data, we identify the two velocity peaks with two spatially distinct components. We conclude that this source is likely to be a compact merger of 2 fairly typical star-forming galaxies with a maximal separation between the two nuclei of ~3kpc. This system is much less luminous and massive than other high-z submm galaxies studied to date, but it bears a close similarity to similarly luminous, dusty starburst resulting from lower-mass mergers in the local Universe.

For more details, see Astronomy & Astrophysics, 434, 819, 2005

PR 1110/04
IRAM PR 1110/04

Q0957+561 revised: CO emission from a disk at z=1.4    M. Krips, R. Neri, A. Eckart, D. Downes, J. Martin-Pintado, P. Planesas University of Cologne, Germany

Q0957+561 at a redshift of z=1.4141, is the first detected gravitationally lensed quasar (Walsh et al. 1979). New IRAM PdBI observations of this system confirm a previous detection of the CO(2-1) line emission by Planesas et al. (1999) towards the southern lensed image B and substantiate a double peaked line profile towards the northern component A.

Our new interferometric CO maps of the host galaxy agree well with HST images and we thus argue that the two velocity components seen at image A arise from molecular gas in the disk of the host galaxy. This hypothesis is also supported by detailed simulations of the gravitational lens effect in Q0957+561 explaining also the absence of the redshifted line towards the lensed image B. While the blueshifted part of the gas emission is located closer to the lens in the projected lens plane and thus deeper in the lens potential so that it is deflected into several images, the redshifted part is associated with a region at a larger distance from the lens where the gravitational potential can only produce a single magnified image. The gas mass of the disk is estimated to 5x1010 sun masses.

For more details, see Astronomy & Astrophysics, 431, 879, 2005

PR 0923/04
IRAM PR 0923/04

A compact starburst core in the dusty Lyman break galaxy Westphal-MD11    A.J. Baker, L.J. Tacconi, R. Genzel, D. Lutz, M.D. Lehnert MPE Garching, Germany

Westphal-MD11 is an unusually dusty z = 2.98 Lyman break galaxy: despite the fact that it is unlensed, its observed 850 micron flux density (5.5 mJy) is comparable to that of the highly magnified system MS1512-cB58 (4.2 mJy). New, extremely deep observations with the PdBI prove that this similarity does not extend to the two systems' molecular line emission. After 42 hours of integration, CO(3-2) emission from WMD11 is not detected (right panel: 3 sigma upper limit 0.11 Jy km/s), in stark contrast to the previously published detection of cB58 (left panel: 5.5 sigma peak 0.37 Jy km/s). Contours in both panels are multiples of 1 sigma after integration over the full (assumed) line widths.

WMD11 can only achieve its very high ratio of dust to molecular gas luminosity if its dust emission arises from a spatially compact structure radiating near its blackbody limit- similar to the central disks seen in local ULIRGs. Since WMD11 shows a merger morphology in optical imaging, such a configuration is not implausible. An intense, centrally concentrated starburst fuelled by a relatively modest molecular gas reservoir is quite different from what is observed in cB58, underlining the diversity of star-forming systems that are selected by the Lyman break technique.

For more details, see Astrophysical Journal, 613, L113, 2004

PR 0329/04
IRAM PR 0519/04

MAMBO observations of a z=4.1 proto-cluster    C. De Breuck, F. Bertoldi, C. Carilli, A. Omont, B. Venemans, H. Rottgering, R. Overzier, M. Reuland, G. Miley, R. Ivison, W. van Breugel European Southern Observatory, Garching, Germany

The z=4.1 radio galaxy TN J1338-1942 is surrounded by a proto-cluster of Ly-alpha emitters and Lyman break galaxies. We have obtained a 1.2mm map of this field using MAMBO at the IRAM 30m (shown as blue S/N contours in the figure).

We detect up to ten mm sources, which represents an overdensity of a factor three compared to blank field MAMBO surveys. Using a deep VLA 1.4 GHz map, we can identify at least half of these faint MAMBO sources in our deep VLT optical images. Very deep optical VLT spectroscopy did not yield redshifts, so alternative redshift determination techniques (e.g. CO spectroscopy) will be needed to determine if these sources are indeed members of this distant proto-cluster. If confirmed, this would reveal a population of dust-obscured galaxies with extremely high star-formation rates, which cannot be identified using optical selection techniques.

For more details, see Astronomy & Astrophysics, 424, 1, 2004

PR 0329/04
IRAM PR 0329/04

Ethylene glycol in comet C/1995 O1 (Hale-Bopp)    J. Crovisier, D. Bockelée-Morvan, N. Biver, P. Colom, D. Despois, D.C. Lis Observatoire de Paris, Meudon, France

We report the detection of ethylene glycol (HOCH2CH2OH) in comet C/1995 O1 (Hale-Bopp) from the analysis of archival radio spectra. About ten rotational lines of the molecule are observed in spectra obtained at the IRAM 30-m telescope and Plateau de Bure interferometer and at the Caltech Submillimeter Observatory, in spring 1997. The identification was made just after the rotational lines of this molecule was included in the Cologne Database for Molecular Spectroscopy. The production rate of ethylene glycol is approximately 0.25% that of water, making it one of the most abundant organic molecules in cometary ices. This detection strengthens the similarity between interstellar and cometary material. It outlines the possible role of cometary impacts in the origin of life by seeding the early Earth with prebiotic molecules.

For more details, see Astronomy & Astrophysics, 418, L35, 2004

PR 0326/04
IRAM PR 0326/04

Molecular hydrogen as baryonic dark matter     A. Heithausen, Radioastronomisches Institut, Universität Bonn, Germany

Unravelling the nature of dark matter is one of the biggest challenges of modern astronomy. An interesting candidate is molecular hydrogen. Because at most temperatures in the interstellar medium it cannot be observed directly, it can be only traced through secondary tracers such as carbon monoxide, CO. Pfenniger & Combes have proposed that most of the dark matter in the outskirts of our Milky Way could be in form of cold molecular gas with a fractal structure. Basic building blocks in their model are so-called clumpuscules with sizes of about 100AU and the mass of Jupiter (1/1000 of the mass of the sun).

High-angular resolution CO observations obtained with the Plateau de Bure Interferometer reveal now that such small structures indeed exist. Feature-less structures seen in single-dish measurements break up into several smaller clumps in the interferometer map (see Figure). At an adopted distance of 100pc their sizes are of order a few hundred AU, some of which are still unresolved at an angular resolution of about 3''. The clumps have a fractal structure with a fractal index between 1.7 and 2.0. Their kinetic temperature is between 7K and 18K. Adopting standard conversion factors masses are about 1/10 of a Jupiter mass for individual clumps and densities are higher than 20000cm3. These structures are so small that it is only possible to detect them with highest angular resolution and sensitivity.

For more details, see 2004, Astrophysical Journal Letters, 606, L13, 2004

PR 1112/03
IRAM PR 1112/03

Atomic Carbon in the Cloverleaf Quasar at z=2.5     A. Weiss, C. Henkel, D. Downes, F. Walter Instituto de Radioastronomia Milimétrica, Spain

We observed the upper fine structure line of neutral carbon (νrest = 809GHz), the CO(3-2) line (νrest = 345GHz) and the 1.2mm continuum emission from H1413+117 (Cloverleaf quasar, z=2.5) using the IRAM interferometer.

Together with the detection of the lower fine structure line (Barvainis et al 1997), the Cloverleaf quasar is now only the second extragalactic system, besides M82, where both carbon lines have convincingly been detected. Our analysis shows that the carbon lines are optically thin and have an excitation temperature of Tex= 30K. CO is subthermally excited and the observed line luminosity ratios are consistent with n(H2)~ 103-4 cm-3 at Tkin= 30-50 K. Using three independent methods (CI, dust, CO) we derive a total molecular gas mass (corrected for magnification) M(H2)~1.2 +/- 0.3 x 1010 solar masses. Our observations suggest that the molecular disk extends beyond the region seen in CO(7-6) to a zone of more moderately excited molecular gas that dominates the global emission in CI, and the low J CO lines.

For more details, see Astronomy & Astrophysics, 409, L41, 2003

PR 1017/03
IRAM PR 1017/03

Powerful CO Emission from Three Submillimeter Galaxies at z=2.4, 2.5 and 3.4     R. Neri, R. Genzel, R.J. Ivison, F. Bertoldi, A.W. Blain, S.C. Chapman, P. Cox, T.R. Greve, A. Omont, D.T. Frayer Institut de Radio Astronomie Millimétrique, France

During the last years significant progress has been made with SCUBA at 850μm and MAMBO at 1.2mm to resolve a significant fraction of the background into a population of faint submillimeter sources. We have now been able to determine accurate redshifts with the Plateau de Bure interferometer and map the molecular CO emission in three of these sources: SMMJ04431+0210, SMMJ09431+4700 and SMMJ16368+4057. Today, these three galaxies more than double the number of millimeter-confirmed SCUBA redshifts.

Figure 1 shows (top) the velocity-integrated naturally-weighted CO maps superposed on optical K (left and right) and I band images, and (bottom) the corresponding spectra with the LSR velocity scaled centered on the CO redshift. Our moderate resolution interferometric observations not only confirm the redshifts identified from rest-frame UV/optical spectroscopy but also reveal that at least some SCUBA galaxies are luminous and gas-rich massive starburst/AGN systems seen at a similar epoch to the UV-bright QSO and Ly-break galaxies populations. As such, the submillimeter population of SCUBA selected galaxies is a crucial key for studying the high-z assembly of mass at the tip of the galaxy luminosity function and a critical test for current galaxy formation scenarios.

For more details, see Astrophysical Journal Letters, 597, L113, 2003

PR 1016/03
IRAM PR 1016/03

A Keplerian Disk in the Red Rectangle?     V. Bujarrabal, R. Neri, J. Alcolea, C. Kahane Observatorio Astronomico Nacional, Spain

The Red Rectangle is a nearby (~400pc) low-mass proto-planetary nebula with an eye-catching reddish bipolar structure in visible light. From different grounds it had been proposed that most of the nebular gas surrounding the Red Rectangle is not escaping from the central star, but lying on a gravitationally bound disk. The detection and so the formation of disks around post-AGB stars could lead to a significant upturn in the understanding of proto-planetary evolution.

We observed molecular CO emission from the Red Rectangle with the IRAM PdBI in the CD set of configurations. Our high-resolution maps (3.6''x1.6'' at 230 GHz) show that the bulk of the CO(2-1) emission is found to arise from a thin disk in the equatorial regions of the Red Rectangle. This flattened region measures 2000 AU (full extent) and is less than 500 AU thick. The gas mass contained in the disk is estimated to about 0.04 solar masses, and the gas velocity increases towards the center with a pattern very much consistent with Keplerian rotation. Figure 1 summarizes these results: (top) position velocity cut in the East-West direction, (middle) spectral profile and (bottom) emission centroids. These observations provide first evidence for the existence of an orbiting molecular disk around the central star of a post-AGB star.

For more details, see Astronomy & Astrophysics, 409, 573, 2003

PR 0528/03
IRAM PR 0528/03

Subarcsecond Millimeter-wave Observations of the Protostellar Collapse Candidate B335: Detection of a Disk and Implications for Envelope Structure     D.W.A. Harvey, D.J. Wilner, P.C. Myers, M. Tafalla, D. Mardones Harvard-Smithsonian Center for Astrophysics, Cambridge, USA

The dense core in the B335 dark globule is generally recognized as the best protostellar collapse candidate. This dense core is nearby (250 pc), isolated, and nearly spherical. It contains a deeply embedded low luminosity young stellar object (3 solar luminosities) discovered at far-infrared wavelengths and detected by IRAS only at λ≥60μm.

We observed dust continuum from B335 at subarcsecond resolution with the IRAM PdBI at wavelengths of 1.2 and 3.0 mm. The observations probe to < 100 AU size scales and reveal a compact source component that we identify with a circumstellar disk. We analyze the data in concert with previous lower resolution PdBI observations and find a best fit density structure for B335 that consists of a power law envelope with index p=1.55 ± 0.04 (r 5000 AU) together with a compact source (FWHM ~ 45 AU) with flux F1.2 21 ±2 mJy. We estimate a systematic uncertainty in the power law index Δ p 0.15, where the largest error comes from the assumed form of the dust temperature falloff with radius. This determination of the inner density structure of B335 has a precision unique amongst protostellar cores, and it is consistent with the r-1.5 profile of gravitational free-fall, in accord with basic expectations for the formation of a star. The flux (and implied mass) of the compact component in B335 is typical of the disks around T Tauri stars.

PR 0122/03
IRAM PR 0122/03

Disappearance of N2H+ from the gas phase in the Class 0 protostar IRAM 04191?     A. Belloche, P. André Laboratoire de Radioastronomie, ENS, and Service d'Astrophysique, CEA/Saclay, France

IRAM 04191+1522 was discovered a few years ago in the 1.3mm dust continuum with MAMBO on the IRAM 30m telescope (André et al. 1999). With an estimated age of ~1-3x 104 yr since the beginning of the accretion phase, it is currently the youngest Class 0 protostar known in the Taurus molecular cloud. It is associated with a powerful bipolar outflow and a prominent infalling envelope also undergoing fast, differential rotation (Belloche et al. 2002).

A new map of this object was obtained in N2H+(1-0) with the Plateau de Bure interferometer. This integrated intensity map reveals a hole of N2H+ emission (blue color) in the inner protostellar envelope whose central position is marked by the black cross, as traced by the centroid of the 1.3mm continuum emission measured with PdBI. Two N2H+ peaks (red color) are observed on either side of the central position, approximately along the direction perpendicular to the outflow axis. A preliminary combination of these PdBI data with short spacings obtained at the 30m telescope is shown in Figure 2. These results suggest that N2H+ disappears from the gas phase above a density of ~106 cm-3.

For more details, see Astronomy & Astrophysics, 419, L35, 2004

PR 0120/03
IRAM PR 0120/03

Molecular gas and dust at z=2.6 in SMM J14011+0252     D. Downes, P. Solomon IRAM, France

We used the IRAM Interferometer to detect CO(3-2), CO(7-6), and 1.3 mm dust continuum emission from the submillimeter galaxy SMM J14011+0252 at a redshift of 2.6.

Contrary to a recent claim that the CO was extended over 6.6'' (57 kpc), the new data yield a size of 2'' x 0.5'' for the CO and the dust. Although previous results placed the CO peak in a region with no visible counterpart, the new maps show the CO and dust are centered on the J1 complex seen on K-band and optical images. We suggest the CO is gravitationally lensed not only by the foreground cluster A1835, but also by an individual galaxy on the line of sight. Comparison of measured and intrinsic CO brightness temperatures indicates the CO size is magnified by a factor of 25 +/- 5. After correcting for lensing, we derive a true CO diameter of ~0.08'' (700 pc), consistent with a compact circumnuclear disk of warm molecular gas similar to that in Arp 220. The high magnification means the true size, far-IR luminosity, star formation rate, CO luminosity, and molecular gas mass are all comparable with those in present-epoch ultraluminous IR galaxies, not with those of a huge, massive, early-universe galactic disk.

For more details, see Astrophysical Journal, 582, 37, 2003

PR 1129/02
IRAM PR 1129/02

The disk/jet system in the high-mass (proto)star IRAS20126+4104     R. Cesaroni, R. Neri, L. Olmi, L. Testi, C.M. Walmsley, P. Hofner Oss.Astr.Arcetri, Italy

Newly born high-mass stars are thought to be surrounded by circumstellar disks as much as less massive, solar type stars. Close to the star, part of the infall is likely to be reversed into outflow, powering collimated molecular jets. An example of this is the luminous source IRAS20126+4104.

The lefthand figure represents a composite map of this object obtained with the Plateau de Bure interferometer. This shows the SiO(2-1) (colour image, resolution 1.8''x1.6'') and CH3OH(2-1) (contours, resolution 2.7''x2.6'') line emission, which clearly demonstrates the presence of a compact molecular core where the source (red star) is embedded and the existence of a bipolar jet aligned in the SE-NW direction. The velocity-position plots of the line emission in various tracers along the SE-NW and NE-SW directions indicated by the lines drawn in the lefthand figure reveal kinematical details. In particular the SE-NW cut shows the presence of a velocity gradient in the SiO(2-1) (colour image) and CH3OH(2-1) (contours) lines, whereas the NE-SW cut demonstrates the existence of a velocity gradient perpendicular to the jet and hence likely associated with a circumstellar disk: in this picture the contours and colour image refer respectively to the CH3OH(2-1) and CH3CN(12-11) line emission.

PR 1022/02
IRAM PR 1022/02

A Very Massive Submillimeter Galaxy at z = 2.8     R. Genzel, A.J. Baker, L.J. Tacconi, D. Lutz, P. Cox S. Guilloteau, A. Omont MPE Garching, Germany

SMMJ02399-0136 is a z=2.808 submillimeter-bright galaxy first detected in the 850 micron SCUBA Cluster Lens Survey. Its rest-frame UV morphology shows two peaks (L1 and L2 in the Keck R-band image at left), one of which coincides with a bright X-ray source (white cross). New 1.2mm continuum observations with the PdBI (contours) have resolved the galaxy's dust emission for the first time; they reveal an east-west elongation consistent with the predicted lensing shear, and a centroid which agrees with the rest-UV/X-ray peak L1. CO(3-2) line emission from the source is also spatially resolved, and shows a double-horned global spectrum which is the classical signature of rotation. On the basis of its dust morphology and gas dynamics, SMMJ02399-0136 appears to contain a massive molecular ring/disk which rotates about a buried type 2 QSO. Its dynamical mass of >3.1011 solar masses within a radius of 8 kpc is surprisingly large relative to the predictions of CDM hierarchical structure formation models, in which the most massive systems tend to be formed by merging at lower redshifts. A quantitative comparison with these models shows that they may underpredict the comoving number densities of massive baryonic systems at z~3 by significant factors.

For more details, see Astrophysical Journal, 584, 633, 2003.

PR 1010/02
IRAM PR 1010/02

Mapping the circumstellar envelope around HD 161769     J. Alcolea, R. Neri, V. Bujarrabal, A. Castro-Carrizo Observatorio Astronomico Nacional, Spain

CO J=2-1 observations with a spatial resolution of ~1'' of the circumstellar envelope around the white-yellow giant HD 161769 have unveiled the structure and kinematics of this nebula, very probably a young progenitor of a bipolar planetary nebula.

When a star like our Sun becomes very old, it gets redder and starts loosing mass at an increasing rate, forming a thick spherical cocoon of gas and dust, which expands into space at a velocity of a few km/s. At the end of this stage (known as the AGB phase) the mass loss is so copious, up to 0.0001 solar masses per year, that the star can not endure this loose of weight for too long. Finaly, after some 1000 yr, it initiates the last journey in its evolution before it dies: the heavy mass loss stops and the star becomes hotter and hotter. This transition is very fast, and hence just a few rare objects in the galaxy that are at this point in their evolution: HD 161769 (also known as IRAS 17436+5003 and V814 Her) is one of these.

As the last layers of dust and gas move away, a cavity forms around the star. This hole can be seen in panel A, where we show the map of the emission at the systemic velocity (marked with a dashed line in panels B and C). Simultaneously, a much lighter but faster collimated flow ignites, excavating a tunnel in the nebula along two opposite directions, and breaking its former spherical symmetry. These two cavities are seen in panel B as two point-symmetric minima in the position vs. velocity diagram for a cut along the symmetry axis of the nebula (the dashed line in panel A). CO emission at velocities larger than the formerly expansion velocity, the wings in the spectrum in panel C, also arise at this point. This fast molecular gas might have been accelerated by the passage of the fast flow (yet unseen). We also plot a sketch of the nebula, showing the slowly expanding gas (in yellow), the two excavated cavities and central hole (in white), and the approaching and receding fast molecular gas (in blue and red respectively). We also indicate the orientation of the symmetry axis of the nebula (dotted line) with respect to the line of sight (arrow).

PR 1009/02
IRAM PR 1009/02

CO emission in a z=3.1 radio galaxy     C. De Breuck, R. Neri, R. Morganti, A. Omont, B. Rocca-Volmerange, D. Stern, M. Reuland, W. van Breugel, H. Rottgering, S.A. Stanford, H. Spinrad, M. Vigotti, M. Wright Institut d'Astrophysique de Paris, France

B3 J2330+3927 is a z=3.087 radio galaxy with bright sub-mm dust emission. The redshifted CO(4-3) emission was detected at the 10sigma level in 27 hours of integration with the Plateau de Bure Interferometer (blue contours, resolution 3.2" x 2.3" at PA=56). This emission coincides with the brightest component in a Keck K-band image (orange), which may pinpoint the position of the AGN inside the host galaxy.

The line emission is approximately 500 km/s wide in the 3mm spectrum, and is remarkably close in velocity space to an associated neutral Hydrogen absorber as seen in the Ly-alpha profile determined from optical spectroscopy. This suggests that the CO and neutral Hydrogen originate from the same gas cloud surrounding this massive galaxy. The mass implied from the CO emission is 100 to 1000 times higher than the estimates determined from the Ly-alpha data.

For more details, see Astronomy & Astrophysics, 401, 911, 2003

PR 0916/02
IRAM PR 0916/02

CO line emission from a Lyman break galaxy     A.J. Baker, L.J. Tacconi, R. Genzel, M.D. Lehnert, D. Lutz MPE Garching, Germany

MS1512+36-cB58 is a z = 2.72 Lyman break galaxy which undergoes a factor of ~30 gravitational magnification by a z = 0.37 foreground galaxy cluster. As a result, it is the optically brightest representative of an important population of low-metallicity, high-redshift, star-forming systems. Previous studies at other facilities had failed to detect molecular line emission from cB58. After 32 hours of PdBI observations, however, the galaxy's CO(3-2) line was successfully detected at the 5 sigma level in the integrated map (contours are multiples of 1 sigma = 0.085 Jy/beam km/s, for a synthesized beam of 8.2"x4.8").

From the integrated line intensity, it appears that cB58 contains enough molecular gas to fuel ongoing star formation at the current rate for the next few hundred million years. From the line width (channels are 48 km/s wide in the spectrum), cB58's gas mass fraction is estimated to lie in the range of 10-50%.

For more details, see Astrophysical Journal, 604, 125, 2004

PR 0628/02
IRAM PR 0628/02

Molecular gas in the warped galaxy NGC3718     M. Krips, A. Eckart, S. Leon, J.-U. Pott University of Cologne, Germany, and the NUGA team

The warped galaxy NGC3718 belongs to the sources studied in the NUGA project (NUclei of GAlaxies). This is an international collaboration that aims at determing the distribution and dynamics of molecular gas in the innermost (~1kpc) region of the nuclei of active galaxies with the highest available spatial resolution to study systematically the different mechanism of gas fueling into AGNs. NGC3718 is not only known for its strongly warped gas disk (simulations are in progress (Pott et al.)) but it also has an impressive dust lane crossing the edge-on disk.

To get a more detailed and complete picture of this galaxy high resolution mosaic observations (beam: 5.8"x3.2"@37; 7 fields mosaic) with the Plateau de Bure Interferometer were carried out at the end of last and the beginning of this year. CO was detected in the innermost region and in the outer parts of the galaxy. The molecular gas content is found to be typical of an elliptical galaxy with a relatively low molecular gas mass. Compared to the Milky Way it is rather a small galaxy (~ half of the size of the Milky Way). The image in the figure shows line and continuum emission and was deconvolved with a bigger beam for representation purposes.

PR 0626/02
IRAM PR 0626/02

CO mapped in a nearby low-declination QSO     M. Krips, T. Bertram, C. Straubmeier, A. Eckart & J. Staguhn, University of Cologne, Germany

The QSO was taken from the COLOGNE NEARBY QSO SAMPLE. This sample is formed by a set of closest QSOs for which detailed studies of the molecular gas distribution and kinematics can be performed on sub-kpc scales. In combination with additional data taken at other wavelengths, a very detailed picture can be given of the properties of these nearby QSO host galaxies allowing furthermore to draw conclusions for highly redshifted QSO host data.

The high resolution (beam: 3.3"x1.9"@-166) observations with the PdB Interferometer have revealed molecular line emission from the QSO (used configuration: BC; integration time: a few hours). The source appears to be aligned north-south with an extension in the line emission of roughly the size of the central bulge in our Milky Way (~4-5kpc). The CO line implies a low total gas mass of roughly a fourth of the one obtained for the Milky Way.