Scientific Results in Press

The chemical composition of the circumstellar envelopes around yellow hypergiant stars

G. Quintana-Lacaci$(^{1})$, V. Bujarrabal$(^{1})$, A. Castro-Carrizo$(^{2})$, and J. Alcolea$(^{3})$
$(^{1})$Observatorio Astronómico Nacional (IGN), Apdo. 112, 28803 Alcalá de Henares, Spain, $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{3})$Observatorio Astronómico Nacional (IGN), Alfonso XII N$^\circ$3, 28014 Madrid, Spain

Abstract:
Context. The yellow hypergiant stars (YHGs) are extremely luminous and massive objects whose general properties are poorly known. Only two of this kind of star show massive circumstellar envelopes, IRC +10420 and AFGL 2343.
Aims. We aim to study the chemistry of the circumstellar envelopes around these two sources, by comparison with well known AGB stars and protoplanetary nebulae. We also estimate the abundances of the observed molecular species.
Methods. We have performed single-dish observations of different transitions for twelve molecular species. We have compared the ratio of the intensities of the molecular transitions and of the estimated abundances in AFGL2343 and IRC+10420 with those in O-rich and C-rich AGB stars and protoplanetary nebulae.
Results. Both YHGs, AFGL2343, and IRC+10420, have been found to have an O-rich chemistry similar to that in O-rich AGB stars, though for AFGL 2343 the emission of most molecules compared with $^{13}$CO lines is relatively weak. Clear differences with the other evolved sources appear when we compare the line intensity corrected for distance and the profile widths which are, respectively, very intense and very wide in YHGs. The abundances obtained for IRC +10420 agree with those found in AGB stars, but in general those found in AFGL 2343, except for $^{13}$CO, are too low. This apparently low molecular abundance in AFGL 2343 could be due to the fact that these molecules are present only in an inner region of the shell where the mass is relatively low.

Appeared in: A&A 471, 551

Formaldehyde as a Tracer of Extragalactic Molecular Gas. I. Para-H$_2$CO Emission from M82

Mühle S.$(^{1})$, Seaquist E. R.$(^{1})$, Henkel C.$(^{2})$
$(^{1})$Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada, $(^{2})$MPIfR, Auf dem Hügel 69, D-53121 Bonn, Germany

Abstract:
Using the IRAM 30 m telescope and the 15 m JCMT, we explore the value of paraformaldehyde (p-H$_2$CO) as a tracer of density and temperature of the molecular gas in external galaxies. The target of our observations are the lobes of the molecular ring around the center of the nearby prototypical starburst galaxy M82. It is shown that p-H$_2$CO provides one of the rare direct molecular thermometers. Reproducing the measured line intensities with a large velocity gradient (LVG) model, we find densities of $n_{H_2} \sim 7\times 10^3$ cm$^{-3}$ and kinetic temperatures of $T_{kin} \sim 200$ K. The derived kinetic temperature is significantly higher than the dust temperature or the temperature deduced from ammonia (NH$_3$) lines, but our results agree well with the properties of the high-excitation component seen in CO. We also present the serendipitous discovery of the $4_2 \rightarrow 3_1$ line of methanol (CH$_3$OH) in the northeastern lobe, which shows - unlike CO and H$_2$CO - significantly different line intensities in the two lobes.

Appeared in: ApJ 671, 1579

The structure and chemistry of the massive shell around AFGL 2343: $^{29}$SiO and HCN as tracers of high-excitation regions

G. Quintana-Lacaci$(^{1})$, V. Bujarrabal$(^{1})$ and A. Castro-Carrizo $(^{2})$
$(^{1})$Observatorio Astronómico Nacional (IGN), Apdo. 112, 28803 Alcalá de Henares, Spain, $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

Abstract:
The yellow hypergiant stars (YHGs) are very massive objects that are expected to pass through periods of intense mass loss during their evolution. Despite of this, massive circumstellar envelopes have been found only in two of them, IRC+10420 and AFGL 2343. The envelopes around these objects and the processes that form them are poorly known. We aim to study the structure, dynamics and chemistry of the envelope around AFGL 2343. We have obtained interferometric maps of the rotational lines $^{29}$SiO $J= 2-1$, HCN $J= 1-0$ and SO $J_K= 2_2 - 1_1$ towards AFGL 2343. We have used an LVG excitation model to analyze the new observations and some previously published line profiles of AFGL 2343. The analysis of the observational data and the fitting results show the presence of a thin, hot and dense component within the previously identified CO shell. This component can be associated with recently shocked gas, but it could also be due to a phase of extremely copious mass loss. We suggest that this shell is the responsible for the whole $^{29}$SiO emission and significantly contributes to the HCN emission. The presence of such a dense shell rich in SiO can be related with that previously found for IRC+10420, which was also suggested to result from a shock. This may be a common feature in the evolution of these stars, as a consequence of the episodic mass loss periods that they pass during their evolution. We present new results for the mass loss pattern, the total mass of the circumstellar envelope and the molecular abundances of some species in AFGL 2343.

Accepted for publication in A&A

CN in prestellar cores

P. Hily-Blant$(^{1})$, M.Walmsley$(^{2})$, G. Pineau des Forêts$(^{3,4})$, and D. Flower$(^{5})$
$(^{1})$IRAM, 300 rue de la Piscine, 38406 Saint-Martin d'Hères, France, $(^{2})$INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy, $(^{3})$IAS (UMR 8617 du CNRS), Université de Paris-Sud, 91405 Orsay, France, $(^{4})$LERMA (UMR 8112 du CNRS), Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France, $(^{5})$Physics Department, The University, Durham DH1 3LE, UK

Abstract:
Context. Determining the structure of and the velocity field in prestellar cores is essential to understanding protostellar evolution.
Aims. We have observed the dense prestellar cores L 1544 and L 183 in the $N = 1 \rightarrow 0$ rotational transition of CN and $^{13}$CN in order to test whether CN is depleted in the highdensity nuclei of these cores.
Methods. We have used the IRAM 30 m telescope to observe along the major and minor axes of these cores. We compare these observations with the 1 mm dust emission, which serves as a proxy for the hydrogen column density.
Results. We find that while CN$(1-0)$ is optically thick, the distribution of $^{13}$CN$(1-0)$ intensity follows the dust emission well, implying that the CN abundance does not vary greatly with density. We derive an abundance ratio of $[CN]/[H2] = 10^{-9}$ in L 183 and $1-3 \times 10^{-9}$ in L 1544, which, in the case of L 183, is similar to previous estimates obtained by sampling lower-density regions of the core.
Conclusions. We conclude that CN is not depleted towards the high-density peaks of these cores and thus behaves like the N-containing molecules N$_2$H$^+$ and NH$_3$. CN is, to our knowledge, the first C-containing molecule to exhibit this characteristic.

Appeared in A&A 480, L5

Dissipative structures of diffuse molecular gas III. Small-scale intermittency of intense velocity-shears

P. Hily-Blant$(^{1,2})$, E. Falgarone$(^{3})$, and J. Pety$(^{1,3})$
$(^{1})$IRAM, 300 rue de la Piscine, 38406 Saint-Martin d'Hères, France, $(^{2})$LAOG, BP 53, 38041 Grenoble Cedex 9, France, $(^{3})$LRA/LERMA, UMR 8112, CNRS, Observatoire de Paris and École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France

Abstract:
Aims. We further characterize the structures tentatively identified on thermal and chemical grounds as the sites of dissipation of turbulence in molecular clouds (Papers I and II).
Methods. Our study is based on two-point statistics of line centroid velocities (CV), computed from three large $^{12}$CO maps of two fields. We build the probability density functions (PDF) of the CO line centroid velocity increments (CVI) over lags varying by an order of magnitude. Structure functions of the line CV are computed up to the 6th order.We compare these statistical properties in two translucent parsec-scale fields embedded in different large-scale environments, one far from virial balance and the other virialized. We also address their scale dependence in the former, more turbulent, field.
Results. The statistical properties of the line CV bear the three signatures of intermittency in a turbulent velocity field: (1) the non- Gaussian tails in the CVI PDF grow as the lag decreases, (2) the departure from Kolmogorov scaling of the high-order structure functions is more pronounced in the more turbulent field, (3) the positions contributing to the CVI PDF tails delineate narrow filamentary structures (thickness $\sim 0.02$ pc), uncorrelated to dense gas structures and spatially coherent with thicker ones ($\sim 0.18$ pc) observed on larger scales. We show that the largest CVI trace sharp variations of the extreme CO linewings and that they actually capture properties of the underlying velocity field, uncontaminated by density fluctuations. The confrontation with theoretical predictions leads us to identify these small-scale filamentary structures with extrema of velocity-shears. We estimate that viscous dissipation at the 0.02 pc-scale in these structures is up to 10 times higher than average, consistent with their being associated with gas warmer than the bulk. Last, their average direction is parallel (or close) to that of the local magnetic field projection.
Conclusions. Turbulence in these translucent fields exhibits the statistical and structural signatures of small-scale and inertial-range intermittency. The more turbulent field on the 30 pc-scale is also the more intermittent on small scales. The small-scale intermittent structures coincide with those formerly identified as sites of enhanced dissipation. They are organized into parsec-scale coherent structures, coupling a broad range of scales.

Appeared in: A&A 481,367

Dust-driven winds and mass loss of C-rich AGB stars with subsolar metallicities

A. Wachter$(^{1,2})$, J. M. Winters $(^{3})$, K.-P. Schröder$(^{4})$, E. Sedlmayr$(^{1})$
$(^{1})$ZAA, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany, $(^{2})$Department of Physics and Astronomy, Division of Astronomy and Space Physics, Uppsala University, Box 515, 75120 Uppsala, Sweden, $(^{3})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{4})$Departamento de Astronomia de la Universidad de Guanajuato, Apartado Postal 144, C.P. 36000, Guanajuato, GTO, Mexico

Abstract:
Aims. We investigate the mass loss of highly evolved, low- and intermediate mass stars and stellar samples with subsolar metallicity. We give a qualitative as well as quantitative description which can be applied to LMC/SMC-type stellar populations.
Methods. For that purpose we apply the same approach as we did for solar metallicity stars and calculate hydrodynamical wind models including dust formation with LMC and SMC abundances under consideration of an adapted model assumption. In particular, we improved the treatment of the radiative transfer problem in order to accommodate larger non-local contributions occurring with smaller opacities. For each wind model we determine an averaged mass-loss rate. The resulting, approximate mass-loss formulae are then applied to well-tested and calibrated stellar evolution calculations in order to quantify the stellar mass loss.
Results. The dynamical models for LMC and SMC metallicity result in mass-loss rates of the same order of magnitude as the solar metallicity models which is in this basic approach in agreement with observations. The hydrodynamical properties like e.g. the outflow velocity differ (for fixed C/O abundance ratio) noticeably, though. While critical luminosities of LMC and solar metallicity models fairly coincide, the SMC models need higher luminosities to develop dust-driven winds.

Appeared in: A&A 486, 497

XPOL - the Correlation Polarimeter at the IRAM 30-m Telescope

C. Thum$(^{1})$, H. Wiesemeyer$(^{2,1})$, G. Paubert$(^{2})$, S. Navarro$(^{2})$ and D. Morris$(^{1})$
$(^{1})$IRAM, 300 Rue de la Piscine, 38406 St. Martin d'Hères, France, $(^{2})$IRAM, Núcleo Central, Avd. Divina Pastora No. 7-9, 18000 Granada, Spain

Abstract:
XPOL, the first correlation polarimeter at a large-millimeter telescope, uses a flexible digital correlator to measure all four Stokes parameters simultaneously, i.e., the total power $I$, the linear polarization components $Q$ and $U$, and the circular polarization $V$. The versatility of the back end provides adequate bandwidth for efficient continuum observations as well as sufficient spectral resolution (40 kHz) for observations of narrow lines. We demonstrate that the polarimetry-specific calibrations are handled with sufficient precision, in particular the relative phase between the Observatory's two orthogonally linearly polarized receivers. The many facets of instrumental polarization are studied at 3 mm wavelength in all Stokes parameters: on-axis with point sources and off-axis with beam maps. Stokes $Q$, which is measured as the power difference between the receivers, is affected by instrumental polarization at the 1.5% level. Stokes $U$ and $V$, which are measured as cross-correlations, are very minimally affected (maximum sidelobes 0.6% [$U$] and 0.3% [$V$]). These levels critically depend on the precision of the receiver alignment. They reach these minimum levels set by small ellipticities of the feed horns when alignment is optimum ( $\leq 0\farcs 3$). A second critical prerequisite for low polarization sidelobes turned out to be the correct orientation of the polarization splitter grid. Its cross-polarization properties are modeled in detail. XPOL observations are therefore limited only by receiver noise in Stokes $U$ and $V$ even for extended sources. Systematic effects set in at the 1.5% level in observations of Stokes $Q$. With proper precautions, this limitation can be overcome for point sources. Stokes $Q$ observations of extended sources are the most difficult with XPOL.

Appeared in PASP 120, 777

NRAO 150: A Recently Identified Quasar Revealing Extreme Non-Ballistic Motion

Agudo I., Bach U., Krichbaum T. P., Marscher A. P., Gonidakis I., Diamond P.J., Alef W., Graham D., Witzel A., Zensus J.A., Bremer M., Acosta-Pulido J.A., Barrena, R.

Abstract:
NRAO 150 - a compact and bright radio to mm source showing core/jet structure - has been recently identified as a quasar at redshift 1.52 through a near-IR spectral observation. To compute quantitative estimates of the basic physical properties of the jet in the source, we have analysed the ultra-high-resolution images from a new sub-milliarcsecond-scale monitoring program of its structure at 86 GHz and 43 GHz with the GMVA and the VLBA, respectively. An additional archival and calibration 43 GHz-VLBA data set, covering from 1997 to 2007, has been used. Our data shows an extreme projected counter-clock-wise jet swing of up to $\sim 11^\circ/$yr within the inner $\sim 61$ pc of the jet, which is associated with a non-ballistic superluminal motion of the jet within this region. We argue that the magnetic field might play an important role in the dynamics of the jet in NRAO 150, which is supported by the large values of the magnetic field strength obtained from our first estimates. The extreme characteristics of the jet swing make NRAO 150 a prime source to study the jet wobbling phenomenon.

Appeared in: ASPC 386, 249

A Global 86 GHZ VLBI Survey of Compact Radio Sources

Sang-Sung Lee$(^{1,2})$, Andrei P. Lobanov$(^{1})$, Thomas P. Krichbaum$(^{1})$, Arno Witzel$(^{1})$, Anton Zensus$(^{1})$, Michael Bremer$(^{3})$, Albert Greve$(^{3})$, Michael Grewing$(^{3})$
$(^{1})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{2})$Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea, $(^{3})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

Abstract:
We present results from a large 86 GHz global very long baseline interferometry (VLBI) survey of compact radio sources. The main goal of the survey is to increase by factors of $3-5$ the total number of objects accessible for future 3 mm VLBI imaging. The survey observations reach a baseline sensitivity of 0.1 Jy and an image sensitivity of better than 10 mJy beam$^{-1}$. A total of 127 compact radio sources have been observed. The observations have yielded images for 109 sources, extending the database of the sources imaged at 86 GHz with VLBI observation by a factor of 5, and only six sources have not been detected. The remaining 12 objects have been detected but could not be imaged due to insufficient closure phase information. Radio galaxies are less compact than quasars and BL Lac objects on the sub-milliarcsecond scale. The flux densities and sizes of the core and jet components of all imaged sources have been estimated using Gaussian model fitting. From these measurements, brightness temperatures have been calculated, taking into account the resolution limits of the data. The cores of 70% of the imaged sources are resolved. The core brightness temperatures of the sources peak at $\sim 10^{11}$ K and only 1% have brightness temperatures higher than $10^{12}$ K. The cores of intraday variable (IDV) sources are smaller in angular size than those of non-IDV sources, and so yield higher brightness temperatures.

Appeared in : Astronomical Journal 136, 159

Molecular Gas in NUclei of GAlaxies (NUGA). IX. The decoupled bars and gas inflow in NGC 2782

Hunt L. K.$(^{1})$, Combes F.$(^{2})$, García-Burillo S.$(^{3})$, Schinnerer E.$(^{4})$, Krips M.$(^{5})$, Baker A. J.$(^{6})$, Boone F.$(^{2})$, Eckart A.$(^{7})$, Léon S.$(^{8})$, Neri R.$(^{9})$, Tacconi L. J$(^{10})$
$(^{1})$INAF-Istituto di Radioastronomia/Sez. Firenze, Largo Enrico Fermi 5, 50125 Firenze, Italy, $(^{2})$Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France, $(^{3})$OAN - Observatorio de Madrid, C/ Alfonso XII, 3, 28014 Madrid, Spain, $(^{4})$Max-Planck-Institut fr Astronomie, Königstuhl 17, 69117 Heidelberg, Germany, $(^{5})$Harvard-Smithsonian Center for Astrophysics, SMA, 645 N. A'ohoku Pl., Hilo, HI 96720, USA, $(^{6})$Department of Physics and Astronomy, Rutgers, State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854, USA, $(^{7})$I. Physikalisches Institut, Universität zu Köln, Zülpicherstraße 77, 50937 Köln, Germany, $(^{8})$IRAM, Avenida Divina Pastora 7, Local 20, 18012 Granada, Spain, $(^{9})$IRAM, 300 Rue de la Piscine, 38406 St.Martin d'Hères, France, $(^{10})$Max-Planck-Institut fr extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany

Abstract:
We present CO$(1-0)$ and CO$(2-1)$ maps of the starburst/Seyfert 1 galaxy NGC 2782 obtained with the IRAM interferometer, at $2\farcs1 \times 1\farcs5$ and $0\farcs7 \times 0\farcs6$ resolution respectively. The CO emission is aligned along the stellar nuclear bar of radius $\sim 1$ kpc, configured in an elongated structure with two spiral arms at high pitch angle $\sim90^\circ$. At the extremity of the nuclear bar, the CO changes direction to trace two more extended spiral features at a lower pitch angle. These are the beginning of two straight dust lanes, which are aligned parallel to an oval distortion, reminiscent of a primary bar, almost perpendicular to the nuclear one. The two embedded bars appear in Spitzer IRAC near-infrared images, and HST color images, although highly obscured by dust in the latter. We compute the torques exerted by the stellar bars on the gas, and find systematically negative average torques down to the resolution limit of the images, providing evidence of gas inflow tantalizingly close to the nucleus of NGC 2782. We propose a dynamical scenario based on numerical simulations to interpret coherently the radio, optical, and molecular gas features in the center of the galaxy. Star formation is occurring in a partial ring at $\sim 1.3$ kpc radius corresponding to the Inner Lindblad Resonance (ILR) of the primary bar; this ring-like structure encircles the nuclear bar, and is studded with H$\alpha$ emission. The gas traced by CO emission is driven inward by the gravity torques of the decoupled nuclear bar, since most of it is inside its corotation. N-body simulations, including gas dissipation, predict the secondary bar decoupling, the formation of the elongated ring at the $\sim 1$ kpc-radius ILR of the primary bar, and the gas inflow to the ILR of the nuclear bar at a radius of $\sim 200-300$ pc. The presence of molecular gas inside the ILR of the primary bar, transported by a second nuclear bar, is a potential ``smoking gun''; the gas there is certainly fueling the central starburst, and in a second step could fuel directly the AGN.

Appeared in: A&A 482, 133

A Multi-transition HCN and HCO+ Study of 12 Nearby Active Galaxies: Active Galactic Nucleus versus Starburst Environments

Krips M.$(^{1})$, Neri R.$(^{2})$, García-Burillo S.$(^{3})$, Martín S.$(^{1})$, Combes F.$(^{4})$, Graciá-Carpio J.$(^{3})$, Eckart A.$(^{5})$
$(^{1})$Harvard-Smithsonian Center for Astrophysics, SMA project, 60 Garden Street, MS 78 Cambridge, MA 02138, $(^{2})$IRAM, Saint Martin d'Hères, F-38406, France, $(^{3})$Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Calle Alfonso XII 3, 28014 Madrid, Spain, $(^{4})$Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, 75014 Paris, France, $(^{5})$Universität zu Köln, I. Physikalisches Institut, Zülpicher Straße 77, 50937 Köln, Germany

Abstract:
Recent studies have indicated that the HCN - to - CO$(J=1-0)$ and HCO$^+$ - to - HCN$(J=1-0)$ ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to study the molecular gas properties in active galaxies and search for differences between AGN and SB environments, we observed the HCN$(J=1-0)$, $(J=2-1)$, $(J=3-2)$, HCO$^+(J=1-0)$, and HCO$^+(J=3-2)$ emission with the IRAM 30 m in the center of 12 nearby active galaxies which either exhibit nuclear SB and/or AGN signatures. Consistent with previous results, we find a significant difference of the HCN$(J=2-1)$- to- HCN$(J=1-0)$, HCN$(J=3-2)$- to- HCN$(J=1-0)$, HCO$^+(J=3-2)$- to -HCO$^+(J=1-0)$, and HCO$^+$- to - HCN intensity ratios between the sources dominated by an AGN and those with an additional or pure central SB: the HCN, HCO$^+$, and HCO$^+$ - to - HCN intensity ratios tend to be higher in the galaxies of our sample with a central SB as opposed to the pure AGN cases, which show rather low intensity ratios. Based on an LVG analysis of these data, i.e., assuming purely collisional excitation, the (average) molecular gas densities in the SB-dominated sources of our sample seem to be systematically higher than in the AGN sources. The LVG analysis seems to further support systematically higher HCN and/or lower HCO$^+$ abundances as well as similar or higher gas temperatures in AGNs compared to the SB sources of our sample. In addition, we find that the HCN- to- CO ratios decrease with increasing rotational number J for the AGNs while they stay mostly constant for the SB sources.

Appeared in: ApJ 677, 262

Submillimeter Galaxies at $z \sim 2$: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H$_2$ Conversion Factor

Tacconi L. J.$(^{1})$, Genzel R.$(^{1,2})$, Smail I.$(^{3})$, Neri R.$(^{4})$, Chapman S. C.$(^{5})$ Ivison R. J.$(^{6,7})$, Blain A.$(^{8})$, Cox P.$(^{4})$, Omont A.$(^{9})$, Bertoldi F.$(^{10})$, Greve T.$(^{11})$, Förster Schreiber N. M.$(^{1})$, Genel S.$(^{1})$, Lutz D.$(^{1})$, Swinbank A. M.$(^{3})$; Shapley A. E.$(^{12})$, Erb D. K.$(^{13})$, Cimatti A.$(^{14})$, Daddi E.$(^{15})$; Baker, A. J.$(^{16})$
Affiliation: $(^{1})$MPE, Giessenbachstrasse 1, D-85741 Garching, Germany, $(^{2})$Department of Physics, University of California, Le Conte Hall, Berkeley, CA, 94720, $(^{3})$Institute for Computational Cosmology, Durham University, Durham, United Kingdom, $(^{4})$IRAM, St. Martin d'Hères, France, $(^{5})$Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, United Kingdom, $(^{6})$UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom $(^{7})$Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom, $(^{8})$Astronomy 105-24, California Institute of Technology, Pasadena, CA 91125, $(^{9})$CNRS and Institut d'Astrophysique de Paris, 98 bis boulevard Arago, 75014 Paris, France, $(^{10})$AIUB, Bonn, Germany, $(^{11})$MPIA, Königsstuhl 17, D-68117 Heidelberg, Germany, $(^{12})$Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, $(^{13})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, $(^{14})$Dipartimento di Astronomia-Alma Mater Studiorum-Università di Bologna, Via Ranzani 1, I-40127 Bologna, Italy, $(^{15})$Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, DAPNIA/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette, France, $(^{16})$Department of Physics and Astronomy, Rutgers, State University of New Jersey, 136 Frelinghuysen Road Piscataway, NJ 08854

Abstract:
We report subarcsecond resolution IRAM PdBI millimeter CO interferometry of four $z \sim 2$ submillimeter galaxies (SMGs), and sensitive CO$(3-2)$ flux limits toward three $z \sim 2$ UV/optically selected star-forming galaxies. The new data reveal for the first time spatially resolved CO gas kinematics in the observed SMGs. Two of the SMGs show double or multiple morphologies, with complex, disturbed gas motions. The other two SMGs exhibit CO velocity gradients of $\sim 500$ km s$^{-1}$ across $\leq 0\farcs2$ (1.6 kpc) diameter regions, suggesting that the star-forming gas is in compact, rotating disks. Our data provide compelling evidence that these SMGs represent extreme, short-lived ``maximum'' star-forming events in highly dissipative mergers of gas-rich galaxies. The resulting high-mass surface and volume densities of SMGs are similar to those of compact quiescent galaxies in the same redshift range and much higher than those in local spheroids. From the ratio of the comoving volume densities of SMGs and quiescent galaxies in the same mass and redshift ranges, and from the comparison of gas exhaustion timescales and stellar ages, we estimate that the SMG phase duration is about 100 Myr. Our analysis of SMGs and optically/UV selected high-redshift star-forming galaxies supports a ``universal'' Chabrier IMF as being valid over the star-forming history of these galaxies. We find that the $^{12}$CO luminosity to total gas mass conversion factors at $z\sim 2-3$ are probably similar to those assumed at $z\sim 0$. The implied gas fractions in our sample galaxies range from 20% to 50%.

Appeared in ApJ 680, 246

Testing the evolutionary link between submillimetre galaxies and quasars: CO observations of QSOs at $z \sim 2$

K. E. K. Coppin$(^{1})$, A. M. Swinbank$(^{1})$, R. Neri$(^{2})$, P. Cox$(^{2})$, D. M. Alexander$(^{3})$, Ian Smail$(^{1})$, M. J. Page$(^{4})$, J. A. Stevens$(^{5})$, K. K. Knudsen$(^{6})$, R. J. Ivison$(^{7,8})$, A. Beelen$(^{9})$, F. Bertoldi$(^{6})$ and A. Omont$(^{10})$
$(^{1})$Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE, $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{3})$Department of Physics, Durham University, South Road, Durham DH1 3LE, $(^{4})$UCL, Mullard Space Science Laboratory, Holmbury St Mary, Dorking RH5 6NT, $(^{5})$Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, $(^{6})$Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany, $(^{7})$Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, $(^{8})$UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, $(^{9})$Institut d'Astrophysique Spatiale, Université Paris-Sud, F-91405 Orsay, France, $(^{10})$Institut d'Astrophysique de Paris, Université Pierre & Marie Curie, 98 bis Boulevard Arago, F-75014 Paris, France

Abstract:
We have used the IRAM Plateau de Bure millimetre interferometer and the UKIRT $1-5 \mu$m Imager Spectrometer (UIST) to test the connection between the major phases of spheroid growth and nuclear accretion by mapping CO emission in nine submillimetre-detected QSOs at $z = 1.7-2.6$ with black hole (BH) masses derived from near-infrared spectroscopy. When combined with one QSO obtained from the literature, we present sensitive CO$(3-2)$ or CO$(2-1$) observations of 10 submillimetre-detected QSOs selected at the epoch of peak activity in both QSOs and submillimetre (submm) galaxies (SMGs). CO is detected in 5/6 very optically luminous ($M_B \sim -28$) submm-detected QSOs with BH masses $M_{BH} \simeq 10^9 - 10^{10} \mbox{M$_\odot$}$, confirming the presence of large gas reservoirs of $M_{gas} \simeq 3.4 \times 10^{10}\mbox{M$_\odot$}$. Our BH masses and dynamical mass constraints on the host spheroids suggest, at face value, that these optically luminous QSOs at $z = 2$ lie about an order of magnitude above the local BH - spheroid relation, $M_{BH}/M_{sph}$, although this result is dependent on the size and inclination of the CO-emitting region. However, we find that their BH masses are $\sim 30$ times too large and their surface density is $\sim 300$ times too small to be related to typical SMGs in an evolutionary sequence. Conversely, we measure weaker CO emission in four fainter ($M_B \sim -25$) submm-detected QSOs with properties, BH masses ( $M_{BH} \simeq 5 \times 10^8\mbox{M$_\odot$}$), and surface densities similar to SMGs. These QSOs appear to lie near the local $M_{BH}/M_{sph}$ relation, making them plausible ``transition objects'' in the proposed evolutionary sequence linking QSOs to the formation of massive young galaxies and BHs at high redshift. We show that SMGs have a higher incidence of bimodal CO line profiles than seen in our QSO sample, which we interpret as an effect of their relative inclinations, with the QSOs seen more face-on. Finally, we find that the gas masses of the four fainter submm-detected QSOs imply that their star formation episodes could be sustained for $\sim 10$ Myr, and are consistent with representing a phase in the formation of massive galaxies which overlaps a preceding SMG starburst phase, before subsequently evolving into a population of present-day massive ellipticals.

Appeared in: MNRAS 389, 45

The Dusty Disk around VV Serpens

Alonso-Albi T.$(^{1})$, Fuente A.$(^{1})$, Bachiller R.$(^{1})$, Neri R.$(^{2})$, Planesas P.$(^{1})$, Testi L.
$(^{1})$Observatorio Astronómico Nacional, Aptdo. Correos 112, 28803 Alcalá de Henares (Madrid), Spain, $(^{2})$IRAM, 300 rue de la Piscine, Domaine Universitaire de Grenoble, F-38406 St. Martin d'Hères, France, $(^{3})$INAF-Osservatorio Astrofisico de Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy

Abstract:
We have carried out observations at millimeter and centimeter wavelengths toward VV Ser using the Plateau de Bure Interferometer and the Very Large Array. This allows us to compute the SED from near infrared to centimeter wavelengths. The modeling of the full SED has provided insight into the dust properties and a more accurate value of the disk mass. The mass of dust in the disk around VV Ser is found to be about $4\times 10^{-5}\mbox{M$_\odot$}$, i.e., 400 times larger than previous estimates. Moreover, the SED can only be accounted for assuming dust stratification in the vertical direction across the disk. The existence of small grains ($0.25-1 \mu$m) in the disk surface is required to explain the emission at near- and mid-infrared wavelengths. The fluxes measured at millimeter wavelengths imply that the dust grains in the midplane have grown up to very large sizes, at least to some centimeters.

Appeared in: ApJ 680, 1289

Tentative detection of phosphine in IRC +10216

M. Agúndez$(^{1})$, J. Cernicharo$(^{1})$, J. R. Pardo$(^{1})$, M. Guélin$(^{2,3})$, and T. G. Phillips$(^{4})$
$(^{1})$Departamento de Astrofísica Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain, $(^{2})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, $(^{3})$LERMA/École Normale Supérieure, 24 rue Lhomond, 75231 Paris, France, $(^{4})$California Institute of Technology, Downs Laboratory of Physics 320-47, Pasadena, CA 91125, USA

Abstract:
Aims. The $J_K = 1_0 - 0_0$ rotational transition of phosphine (PH$_3$) at 267 GHz has been tentatively identified with a $T_{MB} \sim 40$ mK spectral line observed with the IRAM 30-m telescope in the C-star envelope IRC +10216.
Methods. A radiative transfer model was used to fit the observed line profile.
Results. The derived PH3 abundance relative to H$_2$ is $6 \times 10^{-9}$, although it may have a large uncertainty due to the lack of knowledge about the spatial distribution of this species. If our identification is correct, it implies that PH$_3$ has a similar abundance to what is reported for HCP in this source and that these two molecules (HCP and PH$_3$) together take up about 5% of phosphorus in IRC +10216. The abundance of PH$_3$, like that of other hydrides in this source, is not well explained by conventional gas-phase LTE and non-LTE chemical models, and may imply formation on grain surfaces.

Appeared in A&A 485, L33

Observations of CO in the eastern filaments of NGC1275

P. Salomé$(^{1})$, Y. Revaz$(^{2,5})$, F. Combes$(^{2})$, J. Pety$(^{1,2})$, D. Downes$(^{1})$, A. C. Edge$(^{3})$, and A. C. Fabian$(^{4})$ $(^{1})$IRAM, 38406 St. Martin d'Hères, France, $(^{2})$LERMA, Observatoire de Paris, 61 av. de l'Observatoire, 75014 Paris, France, $(^{3})$Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK, $(^{4})$IoA, Madingley Road, Cambridge CB3 OHA, UK, $(^{5})$Laboratoire d'Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Sauverny, Switzerland

Abstract:
We recently found extended CO$(2-1)$ emission from cold molecular gas embedded in the network of H$\alpha$ filaments surrounding the galaxy NGC 1275 (Salome et al. 2006). We now present CO$(2-1)$ interferometer maps of the eastern filaments, at high spatial and spectral resolutions. The cold molecular gas is detected by the Plateau de Bure Interferometer along the eastern filaments over an extent of $15\hbox{$^{\prime\prime}$}$, or with a projected length of 5 kpc. In our $2{\farcs}5$ beam, the main CO filament is mostly unresolved along its minor axis. The multiple peaks along the CO filaments and the low values of the observed CO brightness temperatures imply further unresolved structures that may be giant molecular clouds. These clouds have very narrow line-width emission lines ($\sim 30$ km s$^{-1}$). The CO emission is optically thick. It very likely traces cold clouds bound under their own self-gravity that may be falling back in the gravitational potential well of the galaxy. Such a picture would agree with current models of ``positive feedback'' in which some of the hot gas around NGC1275 (a) is trapped by buoyantly rising bubbles inflated by the energy input of the 3C 84 AGN, (b) subsequently cools efficiently at a larger radius around the edges of the hot bubbles, and (c) then falls back in self-gravitating clouds of molecular gas toward the center of the galaxy.

Appeared in: A&A 383, 793

Cold gas in the Perseus cluster core: excitation of molecular gas in filaments

P. Salomé$(^{1})$, F. Combes$(^{2})$, Y. Revaz$(^{2,6})$, A. C. Edge$(^{3})$, N. A. Hatch$(^{5})$, A. C. Fabian$(^{4})$, and R. M. Johnstone$(^{4})$
$(^{1})$IRAM, 300 rue de la Piscine, 38400 St Martin d'Hères, France, $(^{2})$Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France, $(^{3})$Department of Physics, University of Durham, South Road, Durham DH1 3LEi, UK, $(^{4})$Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK, $(^{5})$Leiden Observatory, 2300 RA Leiden, The Netherlands, $(^{6})$EPFL, Observatoire, 1290 Sauverny, Switzerland

Abstract:
We have recently detected CO lines in the well-known filaments around NGC 1275, the galaxy at the centre of the Perseus cluster of galaxies. These previous observations, with the HERA multi-beam array at the IRAM 30 m telescope enabled us to make a large map of the CO$(2-1)$ line and to see hints of molecular gas far away from the cluster centre. To confirm the presence of CO emission lines in the outer filaments and to study the CO$(2-1)$/CO$(1-0)$ line ratio, we observed seven regions of interest again with the 30 m telescope in both CO$(1-0)$ and CO$(2-1)$. The regions we observed were: the eastern filament, the horseshoe, the northern filament and a southern extension, all selected from H$\alpha$ emission line mapping. Molecular gas is detected in all the observed regions. This result confirms the large extent of the cold molecular gas filaments. We discuss the CO$(2-1)$/CO$(1-0)$ ratios in the filaments. The eastern filament has optically thick gas, whereas further away, the line ratio increases close to values expected for a warmer optically thin medium. We also show CO$(1-0)$ and CO$(2-1)$ lines in 9 regions closer to the centre. The kinematics of the CO is studied here in more detail and confirms that it follows the motions of the warm H$_2$ gas found in the near-infrared. Finally, we searched for dense gas tracers around 3C 84 and claim here the first detection of HCN$(3-2)$.

Appeared in A&A 484, 317