Scientific Results in Press

Mass loss from dusty, low outflow-velocity AGB stars. II. The multiple wind of EP Aquarii

J.M. Winters $(^{1})$, T. Le Bertre $(^{2})$, J. Pety $(^{1,2})$ and R. Neri $(^{1})$
$(^{1})$IRAM, 300 rue de la Piscine, 38406 St Martin d'Hères, France, $(^{2})$LERMA, UMR 8112, Observatoire de Paris, 61 av. de l'Observatoire, F-75014 Paris, France

Abstract:
CO rotational lines are frequently used to trace the outflows from AGB stars. Some profiles are composite, with a narrow component super-imposed on a broader one. These profiles have been interpreted in different ways, calling for episodic mass loss, a bipolar flow, or a circumstellar disk.

To investigate the structure of one of these outflows, we have obtained detailed $^{12}$CO(2-1) and $^{12}$CO(1-0) maps of EP Aqr, a prototypical source with composite CO profiles.

Interferometric data were acquired with the IRAM interferometer and combined with on-the-fly maps obtained at the IRAM 30-m. The resulting maps in $^{12}$CO(2-1) and $^{12}$CO(1-0) cover a field of $100 \hbox{$^{\prime\prime}$}\times 100 \hbox{$^{\prime\prime}$}$ with a spectral resolution of 0.1kms$^{-1}$ and with beams of $1.7 \hbox{$^{\prime\prime}$}\times 1.0 \hbox{$^{\prime\prime}$}$ and $3.5 \hbox{$^{\prime\prime}$}\times 1.8 \hbox{$^{\prime\prime}$}$, respectively.

The source is clearly resolved with a size of about $15\hbox{$^{\prime\prime}$}$ (FWHM). We do not observe any obvious departure from circular symmetry, but there is evidence of a ringed structure in the CO(2-1) map with enhanced intensity at $\sim 3.5\hbox{$^{\prime\prime}$}$ and $7.5\hbox{$^{\prime\prime}$}$ from the central star. The continuum level at 1.3 and 2.6 mm is consistent with the star's photospheric emission. We modeled the spatio-kinematic structure with Monte-Carlo radiative transfer simulations assuming spherical symmetry. We reached a reasonable fit to the map-integrated spectra, but not to the imaging data, possibly because the circumstellar shell of EP Aqr presents inhomogeneities on a scale that is not, or is only barely, resolved in our maps. EP Aqr may be a proto-typical oxygen-rich source for the class of theoretical models exhibiting mass loss variations on a $\sim 100$yr timescale discovered by Winters et al. (2000), which show a layered structure in their extended circumstellar shells.

Appeared in: A&A 475, 559

The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X

F. Motte$(^{1,2})$, S. Bontemps$(^{3})$, P. Schilke$(^{4})$, N. Schneider$(^{1,5})$, K. M. Menten$(^{4})$ and D. Broguière$(^{6})$
$(^{1})$Laboratoire AIM, CEA/DSM - CNRS - Université Paris Diderot, DAPNIA/Service d'Astrophysique, Bât. 709, CEA-Saclay, F-91191 Gif-sur-Yvette Cédex, France, $(^{2})$California Institute of Technology, Downs Laboratory of Physics, Mail Stop 320-47, 1200 E California Blvd, Pasadena, CA 91125, USA, $(^{3})$OASU/LAB-UMR 5804, CNRS - Université Bordeaux 1, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France, $(^{4})$Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{5})$I. Physik. Institut, Universität Köln, 50937 Köln, Germany, $(^{6})$IRAM, 300 rue de la Piscine, F-38406 St. Martin d'Hères, France

Abstract:
Aims. Our current knowledge of high-mass star formation is mainly based on follow-up studies of bright sources found by IRAS, and is thus biased against its earliest phases, inconspicuous at infrared wavelengths. We therefore started searching, in an unbiased way and in the closest high-mass star-forming complexes, for the high-mass analogs of low-mass pre-stellar cores and class 0 protostars. Methods. We have made an extensive 1.2 mm continuum mosaicing study of the Cygnus X molecular cloud complex using the MAMBO cameras at the IRAM 30 m telescope. The $\sim 3 ^{\circ2}$ imaged areas cover all the high-column density ( $A_\mathrm{V} \ge 15$ mag) clouds of this nearby ($\sim 1.7$ kpc) cloud complex actively forming OB stars. We then compared our millimeter maps with mid-infrared images, and have made SiO(2-1) follow-up observations of the best candidate progenitors of high-mass stars. Results. Our complete study of Cygnus X with $\sim 0.09$ pc resolution provides, for the first time, an unbiased census of massive young stellar objects. We discover 129 massive dense cores (FWHM size $\sim 0.1$ pc, $M_{\mbox{\tiny 1.2~mm}} = 4-950~M_\odot$, volume-averaged density $\sim 105$ cm$^{-3}$), among which $\sim 42$ are probable precursors of high-mass stars. A large fraction of the Cygnus X dense cores ($2/3$ of the sample) remain undetected by the MSX satellite, regardless of the mass range considered. Among the most massive ( $\ge 40~\mbox{M$_\odot$}$) cores, infrared-quiet objects are driving powerful outflows traced by SiO emission. Our study qualifies 17 cores as good candidates for hosting massive infrared-quiet protostars, while up to 25 cores potentially host high-luminosity infrared protostars. We fail to discover the high-mass analogs of pre-stellar dense cores ($\sim 0.1$ pc, $> 10^4$ cm$^{-3}$) in Cygnus X, but find several massive starless clumps ($\sim 0.8$ pc, $7 \times 103$ cm$^{-3}$) that might be gravitationally bound. Conclusions. Since our sample is derived from a single molecular complex and covers every embedded phase of high-mass star formation, it gives the first statistical estimates of their lifetime. In contrast to what is found for low-mass class 0 and class I phases, the infrared-quiet protostellar phase of high-mass stars may last as long as their better-known high-luminosity infrared phase. The statistical lifetimes of high-mass protostars and pre-stellar cores ( $\sim 3 \times 10^4$ yr and $< 10^3$ yr) in Cygnus X are one and two order(s) of magnitude smaller, respectively, than what is found in nearby, low-mass star-forming regions. We therefore propose that high-mass pre-stellar and protostellar cores are in a highly dynamic state, as expected in a molecular cloud where turbulent processes dominate.

Appeared in A&A 476, 1243

The dark nature of GRB 051022 and its host galaxy

A. J. Castro-Tirado$(^{1})$, M. Bremer$(^{2})$, S. McBreen$(^{3})$, J. Gorosabel$(^{1})$, S. Guziy$(^{1,4})$, T. A. Fakthullin$(^{5})$, V. V. Sokolov$(^{5})$, R. M. González Delgado$(^{1})$, G. Bihain$(^{6,7})$, S. B. Pandey$(^{1,8})$, M. Jelínek$(^{1})$, A. de Ugarte Postigo$(^{1})$, K. Misra$(^{9})$, R. Sagar$(^{9})$, P. Bama$(^{10})$, A. P. Kamble$(^{11})$, G. C. Anupama$(^{12})$, J. Licandro$(^{4,13})$, D. Pérez-Ramírez$(^{14})$, D. Bhattacharya$(^{15,11})$, F. J. Aceituno$(^{1})$, and R. Neri$(^{2})$
$(^{1})$Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 3.004, 18.080 Granada, Spain, $(^{2})$Institute de Radioastronomie Milimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d'Hères, France, $(^{3})$Max-Planck-Institut für extraterrestrische Physik, 85748 Garching, Germany, $(^{4})$Nikolaev State University, Nikolskaya 24, 54030 Nikolaev, Ukraine, $(^{5})$Special Astrophysical Observatory (SAO-RAS), Nizhnij Arkhyz, Karachai-Cirkassian Rep. 369167, Russia, $(^{6})$Instituto de Astrofísica de Canarias (IAC), Via Láctea s/n, La Laguna, Tenerife, Spain, $(^{7})$Consejo Superior de Investigaciones Científicas (CSIC), Spain, $(^{8})$Mullard Space Science Labratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK, $(^{9})$Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263 129, India, $(^{10})$Centre for Research and Education in Science and Technology (CREST), Indian Institute of Astrophysics Shidlaghatta Road, Hosakote 562 114, India, $(^{11})$Raman Research Institute (RRI), Bangalore 560 080, India, $(^{12})$Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India, $(^{13})$Isaac Newton Group of Telescopes, PO Box 321, 38700 Santa Cruz de la Palma (Tenerife), Spain, $(^{14})$Departamento de Física, EPS, Universidad de Jaén, Campus Las Lagunillas s/n, A3, 23071 Jaén, Spain, $(^{15})$Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India

Abstract:
Aims. We present multiwavelength (X-ray/ optical/ near-infrared/ millimetre) observations of GRB 051022 between 2.5 h and 1.15 yr after the event. It is the most intense gamma-ray burst ( $\sim 10^{-4}$ erg cm$^{-2}$) detected by HETE-2, with the exception of the nearby GRB 030329.

Methods. Optical and near infrared observations did not detect the afterglow despite a strong afterglow at X-ray wavelengths. Millimetre observations at Plateau de Bure (PdB) detected a source and a flare, confirming the association of this event with a moderately bright ($R = 21.5$) galaxy.

Results. Spectroscopic observations of this galaxy show strong [O II], H$\beta$ and [O III] emission lines at a redshift of 0.809. The spectral energy distribution (SED) of the galaxy implies $A_V {\rm (rest frame)} = 1.0$ and a starburst occuring $\sim25$ Myr ago, during which the star-forming-rate reached $\sim 50 \mbox{M$_\odot$}/$yr. In conjunction with the spatial extent ( $1\hbox{$^{\prime\prime}$}$) it suggests a very luminous ($M_V = - 21.8$) blue compact galaxy, for which we also find $Z\sim Z_\odot$. The X-ray spectrum shows evidence of considerable absorption by neutral gas with $N_{\rm H, X-ray} = 3.47^{+0.48}_{-0.47} \times 10^{22}$ cm$^{-2}$ (rest frame). Absorption by dust in the host galaxy at $z = 0.809$ certainly cannot account for the non-detection of the optical afterglow, unless the dust-to-gas ratio is quite different than that seen in our Galaxy (i.e. large dust grains).

Conclusions. It is likely that the afterglow of the dark GRB 051022 was extinguished along the line of sight by an obscured, dense star forming region in a molecular cloud within the parent host galaxy. This galaxy is different from most GRB hosts being brighter than $L^{*}$ by a factor of 3. We have also derived a $SFR \sim 50 \mbox{M$_\odot$}$/yr and predict that this host galaxy will be detected at sub-mm wavelengths.

Appeared in: A&A 475, 101

Multifrequency Observations of the Blazar 3C 279 in January 2006

W. Collmar$(^{1})$, M. Böttcher$(^{2})$, T. Krichbaum$(^{3})$, E. Bottacini$(^{1})$, V. Burwitz$(^{1})$, A. Cucchiara$(^{4})$, D. Grupe$(^{4})$, M. Gurwell$(^{5})$, P. Kretschmar$(^{6})$, K. Pottschmidt$(^{7})$, M. Bremer$(^{8})$, S. Leon$(^{9})$, H. Ungerechts$(^{9})$, P. Giommi$(^{10})$, M. Capalbi$(^{10})$, and the WEBT collaboration
$(^{1})$Max-Planck-Institut für extraterrestrische Physik, P.O. Box 1312, 85741 Garching, Germany, $(^{2})$Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA, $(^{3})$Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{4})$Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA, $(^{5})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA, $(^{6})$European Space Astronomy Centre (ESAC), European Space Agency, PO Box 50727, 28080, Madrid, Spain, $(^{7})$CASS, Code 0424, University of California at San Diego, La Jolla, CA 92093, USA, $(^{8})$IRAM, Avenida Divina Pastora 7, Local 20, E-18012 Granada, Spain, $(^{9})$IRAM, 300 rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d'Hères, France, $(^{10})$ASI Science Data Center, ASDC c/o ESRIN, via G. Galilei, 00044 Frascati, Italy

Abstract:
We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent $\gamma -$ray blazar 3C 279, which was organised around an INTEGRAL ToO observation in January 2006, and triggered on its optical state. The variable blazar was observed at an intermediate optical state, and a well-covered multifrequency spectrum from radio to hard X-ray energies could be derived. The SED shows the typical two-hump shape, the signature of non-thermal synchrotron and inverse- Compton (IC) emission from a relativistic jet. By the significant exposure times of INTEGRAL and Chandra, the IC spectrum (0.3 - 100 keV) was most accurately measured, showing - for the first time - a possible bending. A comparison of this 2006 SED to the one observed in 2003, also centered on an INTEGRAL observation, during an optical low-state, reveals the surprising fact that 2013 despite a significant change at the high-energy synchrotron emission (near-IR/optical/UV) - the rest of the SED remains unchanged. In particular, the low-energy IC emission (X- and hard X-ray energies) remains the same as in 2003, proving that the two emission components do not vary simultaneously, and provides strong constraints on the modelling of the overall emission of 3C 279.

Appeared in Proc. of the 6th INTEGRAL workshop "The Obscured Universe" (Moscow, July 2-8, 2006), eds. S. Grebenev, R. Sunyaev, C. Winkler, ESA SP 622 (2006)

Molecular gas in QSO host galaxies at $z > 5$

R. Maiolino$(^{1})$, R. Neri$(^{2})$, A. Beelen$(^{3})$, F. Bertoldi$(^{4})$, C. L. Carilli$(^{5})$, P. Caselli$(^{6,7})$, P. Cox$(^{2})$, K. M.Menten$(^{8})$, T. Nagao$(^{6,9})$, A. Omont$(^{10})$, C. M.Walmsley$(^{6})$, F. Walter$(^{11})$, and A.Weiß$(^{8})$
$(^{1})$INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy $(^{2})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France, $(^{3})$Institut d'Astrophysique Spatiale, Universitè Paris-Sud, 91405 Orsay, France, $(^{4})$Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany, $(^{5})$National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA, $(^{6})$INAF - Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy, $(^{7})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge, MA 02138, USA, $(^{8})$Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{9})$National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan, $(^{10})$Institut d'Astrophysique de Paris, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France, $(^{11})$Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Abstract:
We present observations with the IRAM Plateau de Bure Interferometer of three QSOs at $z > 5$ aimed at detecting molecular gas in their host galaxies as traced by CO transitions. CO $(5-4)$ is detected in SDSS J033829.31+002156.3 at $z = 5.0267$, placing it amongst the most distant sources detected in CO. The CO emission is unresolved with a beam size of $\sim 1\hbox{$^{\prime\prime}$}$, implying that the molecular gas is contained within a compact region, less than $\sim 3$ kpc in radius.We infer an upper limit on the dynamical mass of the CO emitting region of $\sim 3\times 10^{10} \mbox{M$_\odot$}/sin(i)^2$ The comparison with the Black Hole mass inferred from near-IR data suggests that the BH-to-bulge mass ratio in this galaxy is significantly higher than in local galaxies. From the CO luminosity we infer a mass reservoir of molecular gas as high as $M({\rm H}_2) = 2.2\times 10^{10} \mbox{M$_\odot$}$, implying that the molecular gas accounts for a significant fraction of the dynamical mass.When compared to the star formation rate derived from the far-IR luminosity, we infer a very short gas exhaustion timescale ($\sim 10^7$ years), comparable to the dynamical timescale. CO is not detected in the other two QSOs (SDSS J083643.85+005453.3 and SDSS J163033.90+401209.6) and upper limits are given for their molecular gas content. When combined with CO observations of other type 1 AGNs, spanning a wide redshift range ($0 < z < 6.4$), we find that the host galaxy CO luminosity (hence molecular gas content) and the AGN optical luminosity (hence BH accretion rate) are correlated, but the relation is not linear: $L'_{\rm CO} \propto [\lambda L_{\lambda} (4400\AA)]^{0.72}$.Moreover, at high redshifts (and especially at $z > 5$) the CO luminosity appears to saturate. We discuss the implications of these findings in terms of black hole-galaxy co-evolution.

Appeared in: A&A 472, L33

New Plateau de Bure observations of M 1- 92; unveiling the core

Alcolea J.$(^{1})$, Bujarrabal V.$(^{1})$, Neri R.$(^{2})$
$(^{1})$Observatorio Astronómico Nacional (OAN-IGN), $(^{2})$Institut de Radio Astronomie Millimétrique (IRAM)

Abstract:
M 1-92 is a very well studied bipolar pPN that can be considered an archetype of this type of sources; it shows a clear axial symmetry, along with the kinematics characteristic of this class of envelopes around post-AGB stars. We performed sub-arcsecond resolution observations of the $J=2-1$ rotational line of $^{13}$CO in M 1-92 with the new extended configurations of the IRAM Plateau de Bure interferometer, for studying the morphology and velocity field of the molecular gas better in the nebula, particularly in its central parts. We found that the equatorial structure dividing the two lobes is a thin flat disk, which expands radially with a velocity proportional to the distance to the central stellar system. The kinetic age of this equatorial flow is very similar to that measured in the two lobes, suggesting that the whole structure was formed as a result of a single event some 1200 yr ago, after which the nebula reached an expansion velocity field with axial symmetry. The small widths and velocity dispersion in the gas forming the lobe walls confirm that the acceleration responsible for the nebular shape could not last more than $100 - 120$ yr. In view of the similarity to $\eta$ Car, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a common-envelope system. The study of the possible importance of this mechanism in the context of global PNe and pPNe reshaping should be one on the fields in which future ALMA observations will make a crucial contribution.

Appeared in: Ap&SS, 383A

Detection of $1.6 \times 10^{10} \mbox{M$_\odot$}$ of Molecular Gas in the Host Galaxy of the $z = 5.77$ SDSS Quasar J0927+2001

Carilli C.L.$(^{1})$, Neri R.$(^{2})$, Wang R.$(^{1,3})$, Cox P.$(^{2})$, Bertoldi F.$(^{4})$, Walter F.$(^{5})$, Fan X.$(^{6})$, Menten K.$(^{7})$, Wagg J.$(^{1})$, Maiolino R.$(^{8})$, Omont A.$(^{9,10})$, Strauss Michael A.$(^{11})$, Riechers D.$(^{5})$, Lo K.Y.$(^{12})$, Bolatto A.$(^{13})$, Scoville N.$(^{14})$
$(^{1})$National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, $(^{2})$Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406 St. Martin d'Héres, France, $(^{3})$Astronomy Department, Peking University, Beijing 100871, China, $(^{4})$Argelander-Institut für Radioastronomie, Universitat Bonn, auf dem Hügel 71, Bonn 53121, Germany, $(^{5})$Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, Germany, $(^{6})$Steward Observatory, University of Arizona, Tucson, AZ 85721, $(^{7})$Max-Planck-Institut für Radioastronomie, Auf dem Hgel 69, Bonn 53121, Germany, $(^{8})$Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy, $(^{9})$Institut d'Astrophysique de Paris, CNRS, $(^{10})$Universite Pierre et Marie Curie, Paris, France, $(^{11})$Princeton University Observatory, Princeton, NJ 08544, $(^{12})$National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, $(^{13})$Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720, $(^{14})$Robinson Laboratory, California Institute of Technology, Pasadena, CA 91125

Abstract:
We have detected emission by the CO $5-4$ and $6-5$ rotational transitions at $z = 5.7722\pm 0.0006$ from the host galaxy of the SDSS quasar J0927+2001 using the Plateau de Bure interferometer. The peak line flux density for the CO 5-4 line is $0.72 \pm 0.09$ mJy, with a line FWHM = $610 \pm 110$ km s$^{-1}$. The implied molecular gas mass is $(1.6 \pm 0.3) \times 10^{10}\mbox{M$_\odot$}$. We also detect the 90 GHz continuum at $0.12 \pm 0.03$ mJy, consistent with a 47K dust spectrum extrapolated from higher frequencies. J0927+2001 is the second example of a huge molecular gas reservoir within the host galaxy of a quasar within 1 Gyr of the big bang. Observations of J0927+2001 are consistent with a massive starburst coeval with a bright quasar phase in the galaxy, suggesting the rapid formation of both a super-massive black hole through accretion, and the stellar host spheroid, at a time close to the end of cosmic reionization.

Appeared in: ApJ 666, L9

Differential Lensing Effects in High-z Sources: Constraining the Size and Shape of the Emitting Regions

Krips M., Neri R., Eckart A., Barvainis R., Peck A., Downes D., Planesas P., Martín-Pintado J., Iono D., Petitpas G.

Abstract:
One of the greatest obstacles in determining the physical parameters of galaxies in the early universe is our inability to accurately constrain the sizes of the sources detected. Current cutting-edge mm/submm interferometers such as the Submillimeter Array (SMA) and the Plateau de Bure Interferometer IRAM (PdBI) yield angular resolutions of about $1\hbox{$^{\prime\prime}$}$, which is in most cases not sufficient to resolve the observed emission at high $z$. However, if the high-redshift source is gravitationally lensed by an intervening galaxy, the angular resolution can be improved by up to two orders of magnitude, as demonstrated in the case of the Cloverleaf galaxy. Light from extended regions is deflected in a different way than light from compact structures, so that the lensed images set tight constraints on their true sizes and shapes. We will discuss the use of such differential lensing effects for three gravitationally lensed high-redshift quasars: Q0957+561 ($z=1.41$), SBS1520+530 ($z=1.86$), and APM08279+5255 ($z=3.9$). We have recently detected molecular gas emission traced by CO in the first two sources, doubling the number of CO detections in this mostly unexplored redshift range of $z=1-2$. We will be able to use this technique as well to place even tighter constraints on the size of the dust emission in APM08279+5255, using the new very extended configurations of the SMA and PdBI with their angular resolutions of $0{\farcs}3\-0{\farcs}4$.

Appeared in: From Z-Machines to ALMA: (Sub)Millimeter Spectroscopy of Galaxies ASP Conf. Series, Vol. 375, Edts. A.J. Baker, J. Glenn, A.I. Harris, J.G. Mangum and M.S. Yun., p.250

The clumpy structure of the chemically active L1157 outflow

Benedettini M.$(^{1,2})$, Viti S.$(^{2})$, Codella C.$(^{3})$, Bachiller R.$(^{4})$, Gueth F.$(^{5})$, Beltrán M.T.$(^{6})$, Dutrey A.$(^{7})$, Guilloteau S.$(^{7})$
$(^{1})$INAF - Istituto di Fisica dello Spazio Interplanetario, Area di Ricerca di Tor Vergata, via Fosso del Cavaliere 100, 00133 Roma, Italy, $(^{2})$Department of Physics and Astronomy, University College London, Gower Street, London WC1E6BT, $(^{3})$INAF - Istituto di Radioastronomia, Sezione di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy, $(^{4})$Observatorio Astronómico Nacional (IGN), Apartado 1143, E-28800, Alcalá de Henares, Madrid, Spain, $(^{5})$Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France, $(^{6})$Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Catalunya, Spain, $(^{7})$L3AB, Observatoire de Bordeaux, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France

Abstract:
We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH$_3$OH $(2_K-1_K)$, HC$_3$N $(11-10)$, HCN $(1-0)$ and OCS $(7-6)$. Moreover, the bright B1 clump has also been observed at better spatial resolution in CS $(2-1$), CH$_3$OH $(21-11)A^-$ and $^{34}$SO $(32-21)$. These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM 30-m single-dish observations have been resolved into several subclumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the wall of the younger cavity with a clear arch shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated with the older shock episode. The emission of the observed species peaks in different part of the lobe: the eastern clumps are brighter in HC$_3$N $(11-10)$, HCN $(1-0)$ and CS $(2-1)$ while the western clumps are brighter in CH$_3$OH $(2_K-1_K)$, OCS $(7-6)$ and $^{34}$SO $(32-21)$. This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.

Appeared in: MNRAS 381, 1127

The Variable Radio-to-X-Ray Spectrum of the Magnetar XTE J1810-197

Camilo F.$(^{1})$, Ransom S.M.$(^{2})$, Peñalver J.$(^{3})$, Karastergiou A.$(^{4})$, van Kerkwijk M.H.$(^{5})$, Durant M.$(^{6})$, Halpern J.P.$(^{1})$, Reynolds J.$(^{7})$, Thum C.$(^{4})$, Helfand D.J.$(^{8})$, Zimmerman N.$(^{8})$, Cognard I.$(^{9})$
$(^{1})$Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, $(^{2})$National Radio Astronomy Observatory, Charlottesville, VA 22903, $(^{3})$Instituto de Radioastronomía Millimétrica, E-18012 Granada, Spain, $(^{4})$Institut de Radioastronomie Millimétrique, F-38406 Saint Martin d'Hères, France, $(^{5})$Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada, $(^{6})$Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, $(^{7})$Australia Telescope National Facility, CSIRO, Parkes Observatory, Parkes, NSW 2870, Australia., $(^{8})$Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, $(^{9})$Laboratoire de Physique et Chimie de l'Environnement, CNRS, F-45071 Orleans, France

Abstract:
We have observed the 5.54 s anomalous X-ray pulsar XTE J1810-197 at radio, millimeter, and infrared (IR) wavelengths, with the aim of learning about its broadband spectrum. At the IRAM 30 m telescope, we have detected the magnetar at $\nu=88$ and 144 GHz, the highest radio-frequency emission ever seen from a pulsar. At 88 GHz we detected numerous individual pulses, with typical widths $\sim 2$ ms and peak flux densities up to 45 Jy. Together with nearly contemporaneous observations with the Parkes, Nançay, and Green Bank telescopes, we find that in late 2006 July the spectral index of the pulsar was $-0.5\lower.5ex\hbox{$\; \buildrel < \over \sim \;$}\alpha \lower.5ex\hbox{$\; \buildrel < \over \sim \;$}0$ (with flux density $S_v \sim \nu^\alpha$) over the range 1.4-144 GHz. Nine dual-frequency Very Large Array and Australia Telescope Compact Array observations in 2006 May-September are consistent with this finding, while showing variability of $\alpha$ with time. We infer from the IRAM observations that XTE J1810-197 remains highly linearly polarized at millimeter wavelengths. Also, toward this pulsar, the transition frequency between strong and weak scattering in the interstellar medium may be near 50 GHz. At Gemini, we detected the pulsar at $2.2 \mu$m in 2006 September, at the faintest level yet observed, $K_s=21.89\pm 0.15$. We have also analyzed four archival IR Very Large Telescope observations (two unpublished), finding that the brightness fluctuated within a factor of 2-3 over a span of 3 years, unlike the monotonic decay of the X-ray flux. Thus, there is no correlation between IR and X-ray flux, and it remains uncertain whether there is any correlation between IR and radio flux.

Appeared in: ApJ 669, 561

Particularly efficient star formation in M 33

Gardan E.$(^{1})$, Braine J.$(^{1})$, Schuster K.F.$(^{2})$, Brouillet N.$(^{1})$, Sievers A.$(^{3})$
$(^{1})$Université Bordeaux 1; CNRS; Laboratoire d'Astrophysique, Observatoire de Bordeaux, OASU; UMR 5804, 33270 Floirac, France, $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint-Martin-d'Hères, France, $(^{3})$IRAM, Avenida Divina Pastora 7, Local 20, E-18012 Granada, Spain

Abstract:
The Star Formation (SF) rate in galaxies is an important parameter at all redshifts and evolutionary stages of galaxies. In order to understand the increased SF rates in intermediate redshift galaxies one possibility is to study star formation in local galaxies with properties frequently found at this earlier epoch like low metallicity and small size. We present sensitive observations of the molecular gas in M 33, a small Local Group spiral at a distance of 840 kpc which shares many of the characteristics of the intermediate redshift galaxies. The observations were carried out in the CO(2-1) line with the HERA heterodyne array on the IRAM 30 m telescope. A $11^\prime \times 22^\prime$ region in the northern part of M 33 was observed, reaching a detection threshold of a few $10^3\mbox{M$_\odot$}$. The correlation in this field between the CO emission and tracers of SF ($8 \mu$m, $24\mu$m, H$\alpha$, FUV) is excellent and CO is detected very far North, showing that molecular gas forms far out in the disk even in a small spiral with a subsolar metallicity. One major molecular cloud was discovered in an interarm region with no HI peak and little if any signs of SF - without a complete survey this cloud would never have been found. The radial dependence of the CO emission has a scale length similar to the dust emission, less extended than the H$\alpha$ or FUV. If, however, the $N(H_2) / I_{CO}$ ratio varies inversely with metallicity, then the scale length of the H$_2$ becomes similar to that of the $H\alpha$ or FUV. Comparing the SF rate to the H$_2$ mass shows that M 33, like the intermediate redshift galaxies it resembles, has a significantly higher SF efficiency than large local universe spirals. The data presented here also provide an ideal test for theories of molecular cloud formation and cover a new region in parameter space, where $\sum_{\rm stars} < \sum_{\rm gas}$. We find that a simple pressure-based prescription for estimating the molecular to atomic gas fraction does not perform well for M 33, at least in the outer parts. On the other hand, we show that the molecular gas fraction is influenced by (i) the total Hydrogen column density, dominated in M 33 by the HI, and (ii) the galactocentric distance.

Appeared in: A&A 473, 91

Interferometric detections of GOODS 850-5 at 1 mm and 1.4 GHz

H. Dannerbauer$(^{1})$, F. Walter $(^{1})$, G. Morrison$(^{2,3})$
$(^{1})$Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany, $(^{2})$Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA, $(^{3})$Canada-France-Hawaii Telescope, Kamuela, HI 96743, USA

Abstract:
We have obtained a position (at subarcsecond accuracy) of the submillimeter bright source GOODS 850-5 (also known as GN 10) in the GOODS-North field using the IRAM Plateau de Bure interferometer at 1.25 mm wavelengths (MM J123633+6214.1; flux density: $S(1.25 {\rm mm})=5.0\pm1.0$ mJy). This source has no optical counterpart in deep ACS imaging down to a limiting magnitude of $i(775)=28.4$ mag and its position is coincident with the position found in recent submillimeter mapping obtained at the SMA. Using deep VLA imaging at 20 cm, we find a radio source ( $S(20 {\rm cm})=34.4\pm4.2$ microJy) at the same position that is significantly brighter than reported by Wang and coworkers (but in agreement with a $3\sigma$ detection previously reported by Pope and coworkers). The source is detected by Spitzer in IRAC as well as at 24 mm. We apply different photometric redshift estimators using measurements of the dusty, mid/far-infrared part of the SED and derive a redshift $z \sim 4$. Given our detection in the millimeter and radio we consider a significantly higher redshift (e.g., $z \sim 6$ recently proposed by Wang and coworkers) unlikely. MM J123633+6214.1 alias GOODS 850-5 nevertheless constitutes a bright represen- tative of the high-redshift tail of the submillimeter galaxy population that may contribute a significant fraction to the (sub)millimeter background.

Appeared in ApJL, 673, L127

Detection of amino acetonitrile in Sgr B2(N)

A. Belloche$(^{1})$, K. M. Menten$(^{1})$, C. Comito$(^{1})$, H. S. P. Müller$(^{1,2})$, P. Schilke$(^{1})$, J. Ott$(^{3,4})$, S. Thorwirth1$(^{1})$, and C. Hieret$(^{1})$
$(^{1})$Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany, $(^{2})$I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany, $(^{3})$CSIRO Australia Telescope National Facility, Cnr Vimiera & Pembroke Roads, Marsfield NSW2122, Australia, $(^{4})$National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA

Abstract:
Context. Amino acids are building blocks of proteins and therefore key ingredients for the origin of life. The simplest amino acid, glycine (NH$_2$CH$_2$COOH), has long been searched for in the interstellar medium but has not been unambiguously detected so far. At the same time, more and more complex molecules have been newly found toward the prolific Galactic center source Sagittarius B2.
Aims. Since the search for glycine has turned out to be extremely difficult, we aimed at detecting a chemically related species (possibly a direct precursor), amino acetonitrile (NH$_2$CH$_2$CN).
Methods. With the IRAM 30m telescope we carried out a complete line survey of the hot core regions Sgr B2(N) and (M) in the 3mm range, plus partial surveys at 2 and 1.3mm. We analyzed our 30m line survey in the LTE approximation and modeled the emission of all known molecules simultaneously. We identified spectral features at the frequencies predicted for amino acetonitrile lines having intensities compatible with a unique rotation temperature. We also used the Very Large Array to look for cold, extended emission from amino acetonitrile.
Results. We detected amino acetonitrile in Sgr B2(N) in our 30m telescope line survey and conducted confirmatory observations of selected lines with the IRAM Plateau de Bure and the Australia Telescope Compact Array interferometers. The emission arises from a known hot core, the Large Molecule Heimat, and is compact with a source diameter of $2\hbox{$^{\prime\prime}$}$ (0.08 pc). We derived a column density of $2.8 \times 10^{16}$ cm$^{-2}$, a temperature of 100 K, and a linewidth of 7 km s$^{-1}$. Based on the simultaneously observed continuum emission, we calculated a density of $1.7 \times 10^8$ cm$^{-3}$, a mass of 2340M$_\odot$, and an amino acetonitrile fractional abundance of $2.2 \times 10^{-9}$. The high abundance and temperature may indicate that amino acetonitrile is formed by grain surface chemistry. We did not detect any hot, compact amino acetonitrile emission toward Sgr B2(M) or any cold, extended emission toward Sgr B2, with column-density upper limits of $6 \times 10^{15}$ and $3 \times 10^{12-14}$cm$^{-2}$, respectively.
Conclusions. Based on our amino acetonitrile detection toward Sgr B2(N) and a comparison to the pair methylcyanide/acetic acid both detected in this source, we suggest that the column density of both glycine conformers in Sgr B2(N) is well below the best upper limits published recently by other authors, and probably below the confusion limit in the 1-3mm range.

Accepted for publication in A&A

Superluminal non-ballistic jet swing in the quasar NRAO 150 revealed by mm-VLBI

Agudo I.$(^{1,2})$, Bach U.$(^{2})$, Krichbaum T.P.$(^{2})$, Marscher A.P.$(^{3})$, Gonidakis I.$(^{4})$, Diamond P.J.$(^{5})$, Perucho M.$(^{2})$, Alef W.$(^{2})$, Graham D.A.$(^{2})$, Witzel A.$(^{2})$, Zensus J.A.$(^{2})$, Bremer M.$(^{6})$, Acosta-Pulido J.A.$(^{7})$, Barrena, R.$(^{7})$
$(^{1})$Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, 18080 Granada, Spain, $(^{2})$Max-Planck-Institut für Radioastronomie, Auf dem Hügel, 69, 53121, Bonn, Germany, $(^{3})$Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA, $(^{4})$National and Kapodestrian University of Athens, Dept. of Astrophysics, Astronomy and Mechanics, 157 83 Athens, Greece, $(^{5})$University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK, $(^{6})$Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{7})$Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38200, La Laguna, Tenerife, Spain

Abstract:
Context: NRAO 150, a compact and bright radio to mm source showing core/jet structure, has been recently identified as a quasar at redshift z = 1.52 through a near-IR spectral observation. Aims: To study the jet kinematics on the smallest accessible scales and to compute the first estimates of its basic physical properties. Methods: We have analysed the ultra-high-resolution images from a new monitoring program at 86 GHz and 43 GHz with the Global mm VLBI Array and the VLBA, respectively. An additional archival calibration VLBA data set, covering the period from 1997 to 2007, has been used. Results: Our data show an extreme projected counter-clockwise jet position angle swing at an angular rate of up to $\approx 11^\circ$ yr within the inner $\approx 3$ pc of the jet, which is associated with a non-ballistic superluminal motion of the jet within this region. Conclusions: The results suggest that the magnetic field could 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. Tables 1-3 and the movie are only available in electronic form at http://www.aanda.org

Appeared in: A&A 476, L17

Detection of circumstellar CH$_2$CHCN, CH$_2$CN, CH$_3$CCH and H$_2$CS

M. Agúndez$(^{1})$, J. P. Fonfría$(^{1})$, J. Cernicharo$(^{1})$, J. R. Pardo$(^{1})$ - M. Guélin$(^{2})$
$(^{1})$Departamento de Astrofísica Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, E-28006 Madrid, Spain, $(^{2})$Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406 St. Martin d'Hères, France

Abstract:
We report on the detection of vinyl cyanide (CH$_2$CHCN), cyanomethyl radical (CH$_2$CN), methylacetylene (CH$_3$CCH) and thioformaldehyde (H$_2$CS) in the C-rich star IRC +10216. These species, all of them known to exist in dark clouds, are detected for the first time in the circumstellar envelope around an AGB star.

These molecules have been detected trough pure rotational transitions in the course of a $\lambda$ 3 mm line survey carried out with the IRAM 30-m telescope. The molecular column densities are derived by constructing rotational temperature diagrams. A detailed chemical model of the circumstellar envelope is used to analyze the formation of these molecular species. We have found column densities in the range 5 $\times$ 10$^{12}$ - 2 $\times$ 10$^{13}$ cm$^{-2}$, which translates to abundances relative to H$_2$ of several 10$^{-9}$. The chemical model is reasonably successful in explaining the synthesis of these molecules in the cold outer envelope through gas phase reactions. We also found that these molecules are most probably excited trough infrared pumping to excited vibrational states. The detection of these species stresses the similarity between the molecular content of cold dark clouds and C-rich circumstellar envelopes. However, some differences in the chemistry are indicated by the fact that in IRC +10216 partially saturated carbon chains are present at a lower level than those which are highly unsaturated, while in TMC-1 both types of species have comparable abundances.

Appeared in A&A 479, 493

Laboratory and Astronomical Detection of the Negative Molecular Ion C$_3$N$^-$

P. Thaddeus$(^{1})$, C. A. Gottlieb$(^{1})$ H. Gupta$(^{1,2})$, S. Brünken$(^{1})$, M.C. McCarthy$(^{1})$, M. Agúndez$(^{3})$, M. Guélin$(^{4})$ and J. Cernicharo$(^{3})$
$(^{1})$Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, and Division of Engineering & Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, $(^{2})$Also: Institute for Theoretical Chemistry, Departments of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712, $(^{3})$Department of Molecular and Infrared Astrophysics, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain, $(^{4})$Insitut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Hères, France

Abstract:
The negative molecular ion C$_3$N$^-$ has been detected at millimeter wavelengths in a low pressure laboratory discharge, and then with frequencies in hand in the molecular envelope of IRC+10216.

Spectroscopic constants derived from laboratory measurements of 12 transitions between 97 and 378 GHz allow the rotational spectrum to be calculated well into the submillimeter-wave band to 0.03 km s$^{-1}$ or better in equivalent radial velocity. Four transitions of C$_3$N$^-$ were detected in IRC+10216 with the IRAM 30 m telescope at precisely the frequencies calculated from the laboratory measurements (see Fig. 7).

Figure 7: Abundances of carbon chain molecules in IRC +10216 and TMC-1. The diagram is an extension of a previous publication. The fractional abundances relative to H$_2$ are computed from the molecular column densities and the total H$_2$ column density. We use N(H$_2$) = 10$^{22}$ cm$^{-2}$ in TMC-1 and N(H$_2$) = 2 $\times$ 10$^{21}$ cm$^{-2}$ in IRC +10216. The latter value corresponds to the total H$_2$ column density contained in an outer shell extending from 2 $\times$ 10$^{16}$ cm to 7 $\times$ 10$^{16}$ cm, where all the molecules considered in the diagram are most probably present.

The detection of C$_3$N$^-$ in IRC+10216 ``rounds out'' the work on the astronomical and subsequent laboratory detection of the isoelectronic pair of carbon chains C$_3$N and C$_4$H which began 30 years ago (Guélin & Thaddeus 1976, Ap.J., 212, L81).

The column density of C$_3$N$^-$ is 0.5% that of C$_3$N, or approximately 20 times greater than that of C$_4$H$^-$ relative to C$_4$H. The C$_3$N$^-$ abundance in IRC+10216 is compared with a chemical model calculation by Petrie & Herbst (1997). An upper limit in TMC-1 for C$_3$N$^-$ relative to C$_3$N ($<$0.8%), and a limit for C$_4$H$^-$ relative to C$_4$H ($<0.004$%) that is 5 times lower than that found in IRC+10216, were obtained from observations with the NRAO 100 m Green Bank Telescope (GBT). The fairly high concentration of C$_3$N$^-$ achieved in the laboratory implies that other molecular anions containing the CN group may be within reach.

Ap.J. Letters 2008, in press

Search for anions in molecular sources: C$_4$H$^-$ detection in L1527

M. Agúndez$(^{1})$, J. Cernicharo$(^{1})$, M. Guélin$(^{2})$, M. Gerin$(^{3})$, M. McCarthy$(^{4})$ and P. Thaddeus$(^{4})$
$(^{1})$Departamento de Astrofísica Molecular e Infrarroja, 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'Héres, France, $(^{3})$LERMA, UMR 8112, CNRS, Observatoire de Paris and École Normale Supérieure, 24 Rue l'Homond, 75231 Paris, France, $(^{4})$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Abstract:
Aiming at exploring how ubiquitous and abundant are molecular anions in the interstellar medium we have embarked on a search for C$_4$H$^-$ with the IRAM-30m telescope toward various dark clouds, low mass star-forming regions and PDRs. We have also searched for CN$^-$, C$_2$H$^-$ and C$_6$H$^-$ in some of the sources. The Letter presents the first results of these searches. We have succeeded in detecting C$_4$H$^-$, through the $J = 9-8$ and $J = 10-9$ rotational transitions, in the low mass star-forming region L1527, confirming the tentative detection of the $J = 9-8$ line recently reported toward this source (see Fig. 8). The [C$_4$H$^-$]/[C$_4$H] ratio found is 0.011 %, which is slightly lower than the value observed in IRC +10216, 0.024 %, but above the 3$\sigma$ upper limit we have derived in TMC-1, $<$ 0.0052 %. We have also derived an upper limit for the [C$_6$H$^-$]/[C$_6$H] ratio in the Horsehead Nebula, and for various anion-to-neutral ratios in the observed sources. These results are compared with recent chemical models.

Figure 8: $J = 9-8$ and $J = 10-9$ transitions of C$_4$H$^-$ observed toward L1527. The spectra were acquired in 13.8 h (83.8 GHz) and 22.1 h (93.1 GHz) of integration time.

Appeared in: A&A 478, L19

Laboratory and Astronomical Detection of the Negative Molecular Ion C$_3$N$^-$

P. Thaddeus,$(^{1})$ C. A. Gottlieb,$(^{1})$ H. Gupta,$(^{1,2})$ S. Brünken,$(^{1})$ M. C. McCarthy,$(^{1})$,M. Agúndez,$(^{3})$, M. Guélin,$(^{4})$ and J. Cernicharo,$(^{3})$
$(^{1})$Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, and Division of Engineering & Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, $(^{2})$Institute for Theoretical Chemistry, Departments of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712, $(^{3})$Department of Molecular and Infrared Astrophysics, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain, $(^{4})$Insitut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Hères, France

Abstract:
The negative molecular ion C$_3$N$^-$ has been detected at millimeter wavelengths in a low pressure laboratory discharge, and then with frequencies in hand in the molecular envelope of IRC+10216.

Spectroscopic constants derived from laboratory measurements of 12 transitions between 97 and 378 GHz allow the rotational spectrum to be calculated well into the submillimeter-wave band to 0.03 km s$^{-1}$ or better in equivalent radial velocity. Four transitions of C$_3$N$^-$ were detected in IRC+10216 with the IRAM 30 m telescope at precisely the frequencies calculated from the laboratory measurements (see Fig. 9). The detection of C$_3$N$^-$ in IRC+10216 ``rounds out'' the work on the astronomical and subsequent laboratory detection of the isoelectronic pair of carbon chains C$_3$N and C$_4$H which began 30 years ago (Guélin & Thaddeus 1976, Ap.J., 212, L81).

The column density of C$_3$N$^-$ is 0.5% that of C$_3$N, or approximately 20 times greater than that of C$_4$H$^-$ relative to C$_4$H. The C$_3$N$^-$ abundance in IRC+10216 is compared with a chemical model calculation by Petrie & Herbst (1997). An upper limit in TMC-1 for C$_3$N$^-$ relative to C$_3$N ($<$0.8%), and a limit for C$_4$H$^-$ relative to C$_4$H ($<0.004$%) that is 5 times lower than that found in IRC+10216, were obtained from observations with the NRAO 100 m Green Bank Telescope (GBT). The fairly high concentration of C$_3$N$^-$ achieved in the laboratory implies that other molecular anions containing the CN group may be within reach.

Accepted for publication in ApJ Letters)

Figure 9: Four transitions of C$_3$N$^-$ observed towards IRC+10216 with the IRAM 30 m telescope. The spectral resolution is 1 MHz and the frequency scale (in the rest frame) is relative to a systemic velocity of $-26.5$ km s$^{-1}$. The positions of the C$_3$N$^-$ lines are indicated by arrows. The line at 106.7 GHz is blended with the intense line of C$_6$H (see simulated profile in the insert), but the blue horn (visible on the shoulder of the intense background lines) is within 0.5 MHz of the precise laboratory determined frequency.

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

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

Abstract:
We report sub-arcsecond 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 $\leq 0{\farcs}2$ (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 time scales and stellar ages, we estimate that the SMG phase duration is about 100 Myrs. 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 12CO 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%.

Accepted for publication in ApJ; available as arXiv:0801.3650v1 [astro-ph]

Molecular gas in NUclei of GAlaxies (NUGA). VIII. The Seyfert 2 NGC 6574

Lindt-Krieg E.$(^{1,2})$, Eckart A.$(^{1,3})$, Neri R.$(^{2})$, Krips M.$(^{4})$, Pott J.-U.$(^{1,5})$, García-Burillo S.$(^{6})$, Combes F.$(^{7})$
$(^{1})$Universität zu Köln, 1.Physikalisches Institut, Zülpicher Straße 77, 50937 Köln, Germany, $(^{2})$Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 St. Martin d'Hères, France, $(^{3})$Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{4})$Smithsonian Astrophysical Observatory (SAO), Submillimeter Array (SMA)645, North A'Ohoku Place, 96720 Hilo, USA, $(^{5})$W.M. Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela, HI 96743, USA, $(^{6})$Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014 Madrid, Spain, $(^{7})$Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France

Abstract:
Within the frame of the NUclei of GAlaxies (NUGA) project, we have determined the distribution and kinematics of the molecular gas within the central kpc with high spatial resolution ($100-150$ pc), for a sample of active galaxies. The goal is to study the gas-fueling mechanisms in AGN. We present interferometric observations of $^{12}$CO$(1-0)$ and $^{12}$CO$(2-1)$ line emission from the Seyfert 2 galaxy NGC 6574, obtained with the IRAM Plateau de Bure Interferometer (PdBI). These data have been combined with 30-m mapping data in these lines to correct for the flux resolved by the interferometer. At an angular resolution of $0\farcs7$ ($\equiv 110$ pc), the $^{12}$CO$(2-1)$ emission is resolved into an inner disk with a radius of 300 pc. The molecular gas in NGC 6574 is primarily distributed in four components: nucleus, bar, spiral arms - winding up into a pseudo-ring - and an extended underlying disk component. For the overall galaxy host, we find a $^{12}$CO$(2-1)$ to $^{12}$CO$(1-0)$ line ratio of $\sim 0.3$ indicative of cold or sub-thermally excited gas. For the nucleus, this ratio is close to unity, indicating emission from dense and warm molecular gas. Modeling the gas kinematics with elliptical orbits shows that the molecular gas in the differentially rotating disk of NGC 6574 is strongly influenced by the presence of a stellar bar. The nuclear component shows an extension toward the southeast that may be an indication of the lopsidedness of the nuclear gas distribution. We computed the gravity torques exerted from the stellar bar on the gas, deriving the gravitational potential from near-infrared images, and weighting the torques by the CO distribution. We find negative torques for the gas inside the ring, since the gas aligned with the bar has a slight advance phase shift, leading the bar. This means that gas is flowing in towards the center, at least down to 400 pc in radius, which can explain the observed high nuclear gas concentration. This concentration corresponds to a possible inner Lindblad resonance of the bar, according to the measured rotation curve. The gas has been piling up in this location quite recently, since no startburst has been observed yet.

Appeared in: A&A 479, 377