Scientific Results in Press

First detections of extragalactic SO₂, NS and NO

S. Martín (¹), R. Mauersberger (¹), J. Martín-Pintado (²), S. García-Burillo (³) and C. Henkel (⁴)
(¹)Instituto de Radioastronomía Milimétrica (IRAM), Avda. Divina Pastora 7 NC, E-18012 Granada, Spain, (²)Departamento de Astrofisíca Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, E-28006 Madrid, Spain, (³)Observatorio Astronómico Nacional (OAN), Apartado 1143, 28800 Alcalá de Henares, Madrid, Spain, (⁴)Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

Abstract:
We report the first detections of SO₂, NS and NO in an extragalactic source, the nucleus of the starburst galaxy NGC253. Five SO₂ transitions, three groups of hyperfine components of NO and five of NS were detected. All three species show large abundances averaged over the inner 200pc of NGC253. With a relative abundance of a few 10^-7, the emission of the NO molecule is similar or even larger than that found in Galactic star forming regions. The derived relative molecular abundances for each molecule have been compared with those of prototypical Galactic molecular clouds. These results seem to confirm that large scale shocks dominate the chemistry of these molecules in the nucleus of NGC253, ruling out a chemistry dominated by PDRs for the bulk of the gas.

Published in A&A 411, L465

From the AGB to the PN Phase with the Plateau de Bure Interferometer

Arancha Castro-Carrizo(¹), Roberto Neri(¹) and Jan Martin Winters(¹)
(¹)Institut de RadioAstronomie Millimétrique (IRAM) 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

Abstract:
In order to understand the origin of the asymmetries and substructures observed in planetary nebulae, it is necessary to improve our knowledge on their progenitors, the circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars and proto-planetary nebulae (PPNe). These nebulae are mainly composed of cool molecular gas and therefore they are accessible to mm-observations. The Plateau de Bure interferometer has played an important role in the advance of our understanding of these objects in the last 10 yrs.

To appear in: Asymmetric Planetary Nebulae III, ASP conf. Series, Edts. M. Meixner, J. Kastner, B.Balick and N. Soker

Molecular Gas in NUclei of GAlaxies (NUGA). I. The counter-rotating LINER NGC 4826

García-Burillo S.(¹), Combes F.(²), Hunt L. K.(³), Boone F.(⁴), Baker A. J.(⁵), Tacconi L. J.(⁵), Eckart A.(⁶), Neri R.(⁷), Leon S.(⁸), Schinnerer E.(⁹) and Englmaier P.(¹⁰)
(¹)Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain, (²)Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France, (³)Istituto di Radioastronomia/CNR, Sez. Firenze, Largo Enrico Fermi, 5, 50125 Firenze, Italy, (⁴)Astronomisches Institut der Ruhr-Universität Bochum, Universitätstrasse 150, 44780, Germany, (⁵)Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany, (⁶)Universität zu Köln, I. Physikalisches Institut, Zülpicherstrasse 77, 50937 Köln, Germany, (⁷)Institut de Radio-Astronomie Millimétrique (IRAM), 300 Rue de la Piscine, 38406 St. Mt. D'Hères, France, (⁸)Instituto de Astrofísica de Andalucía (CSIC), C/Bajo de Huétor, 24, Apartado 3004, 18080 Granada, Spain, (⁹)National Radio Astronomy Observatory, PO Box 0, Socorro, NM87801, USA, (¹⁰)Astronomisches Institut, Universität Basel, Venusstrasse 7, 4102 Binningen, Switzerland

Abstract:
We present new high-resolution observations of the nucleus of the counter-rotating LINER NGC 4826, made in the J=1-0 and J=2-1 lines of 12CO with the IRAM Plateau de Bure mm-interferometer(PdBI).The CO maps, which achieve 0.8arcsec (16 pc) resolution in the 2-1 line, fully resolve an inner molecular gas disk which is truncated at an outer radius of 700 pc. The total molecular gas mass ( $3.1\cdot 10^8 \mbox{M$_\odot$ }$ ) is distributed in a lopsided nuclear disk of 40 pc radius, containing 15% of the total gas mass, and two one-arm spirals, which develop at different radii in the disk. The distribution and kinematics of molecular gas in the inner 1 kpc of NGC 4826 show the prevalence of different types of m=1 perturbations in the gas. Although dominated by rotation, the gas kinematics are perturbed by streaming motions related to the m=1 instabilities. The non-circular motions associated with the inner m=1 perturbations (lopsided instability and inner one-arm spiral) agree qualitatively with the pattern expected for a trailing wave developed outside corotation (``fast'' wave). In contrast, the streaming motions in the outer m=1 spiral are better explained by a ``slow'' wave. A paradoxical consequence is that the inner m=1 perturbations would not favour AGN feeding. An independent confirmation that the AGN is not being generously fueled at present is found in the low values of the gravitational torques exerted by the stellar potential for R< 530 pc. The distribution of star formation in the disk of NGC 4826 is also strongly asymmetrical. The observed asymmetries, revealed by HST images of the inner disk, follow the scales of the various m=1 perturbations identified in the molecular gas disk. Massive star formation is still vigorous, fed by the significant molecular gas reservoir at R< 700 pc. There is supporting evidence for a recent large mass inflow episode in NGC 4826. The onset of m=1 instabilities of the type observed in NGC 4826 may be a consequence of secular evolution of disks with high gas mass contents.

These observations have been made in the context of the NUclei of GAlaxies (NUGA) project, aimed at the study of the different mechanisms for gas fueling of Active Galactic Nuclei (AGN).

Published in A&A 407, 485

Detection of an orbiting gas disk in the Red Rectangle

Bujarrabal V.(¹), Neri R.(²), Alcolea J.(³) and Kahane C.(⁴)
(¹)Observatorio Astronómico Nacional, Apartado 1143, 28800 Alcalá de Henares, Spain, (²)IRAM, 300 rue de la Piscine, 38406 St Martin d'Hères, France, (³)Observatorio Astronómico Nacional, C/Alfonso XII, 3, 28014 Madrid, Spain, (⁴)Laboratoire d'Astrophysique de Grenoble, BP 53, 38041 Grenoble Cedex 9, France

Abstract:
We present interferometric maps of CO emission in the Red Rectangle, a well known protoplanetary nebula. The CO emission is found to arise from a relatively thin equatorial disk, extending about 5 $^{\prime\prime}$ in the direction perpendicular to the symmetry axis of the optical nebula. The velocity dispersion of the emission clearly increases towards the center, in a pattern significantly coincident with that expected for a Keplerian velocity field. Modeling of the CO maps confirms that the emitting gas is probably rotating around the central star(s), with a Kepler-like velocity distribution (at least in the central regions) that would correspond to a central mass $\approx 0.9 \mbox{M$_\odot$ }$. Other possible explanations to the observations are discussed, but are found to be unlikely. Our models also suggest that the density and temperature increase towards the center roughly proportionally to the inverse radius. The asymmetry observed in the line profile and intensity distribution (the red part being stronger) can be explained by self-absorption if, superimposed to the rotation velocity, there is a low radial expansion at a velocity of about 0.4 km s^-1, at least in the outer disk regions. This is the first probable detection of a gas disk in Kepler-like rotation around a post-AGB star.

Published in A&A 409, 573

High-excitation CO in a quasar host galaxy
at z =6.42

Bertoldi F.(¹), Cox P.(²), Neri R.(³), Carilli C. L.(⁴), Walter F.(⁴), Omont A. (⁵), Beelen A.(⁶), Henkel C.(¹), Fan X.(⁷), Strauss Michael A.(⁸) and Menten K. M.(¹)
(¹)Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany, (²)Institut d'Astrophysique Spatiale, Université de Paris XI, 91405 Orsay, France, (³)IRAM, 300 rue de la Piscine, 38406 St-Martin-d'Hères, France, (⁴)National Radio Astronomy Observatory, PO Box, Socorro, NM 87801, USA, (⁵)Institut d'Astrophysique de Paris, CNRS & Université de Paris 6, 98bis bd. Arago, 75014 Paris, France (⁶)Institut d'Astrophysique Spatiale, Université de Paris XI, 91405 Orsay, France, (⁷)Steward Observatory, The University of Arizona, Tucson, AZ 85721, USA, (⁸)Princeton University Observatory, Princeton, NJ 08544, USA

Abstract:
We report the detection of high excitation CO emission from the most distant quasar currently known, SDSS J114816.64+525150.3 (hereafter J1148+5251), at a redshift z=6.419. The CO (J=6-5) and (J=7-6) lines were detected using the IRAM Plateau de Bure interferometer, showing a width of $\approx 280$ km s^-1. An upper flux limit for the CO (J=1-0) line was obtained from observations with the Effelsberg 100-meter telescope. Assuming no gravitational magnification, we estimate a molecular gas mass of $\approx 2\times 10^{10} \mbox{M$_\odot$ }$. Using the CO (3-2) observations by Walter et al. (2003), a comparison of the line flux ratios with predictions from a large velocity gradient model suggests that the gas is likely of high excitation, at densities $\approx 104.5$ cm^-3 and a temperature $\approx 100$ K. Since in this case the CO lines appear to have moderate optical depths, the gas must be extended over a few kpc. The gas mass detected in J1148+5251 can fuel star formation at the rate implied by the far-infrared luminosity for less than 10 million years, a time comparable to the dynamical time scale of the region. The gas must therefore be replenished quickly, and metal and dust enrichment must occur fast. The strong dust emission and the massive, dense gas reservoir at z $\approx 6.4$ provide further evidence that vigorous star formation is co-eval with the rapid growth of massive black holes at these early epochs of the Universe.

Appeared in A&A 409, L47

Interferometric Observations of Powerful CO Emission from Three Submillimeter Galaxies at z=2.39, 2.51, and 3.35

Neri R.(¹), Genzel R.(^2,3), Ivison R. J.(⁴), Bertoldi F.(⁵), Blain A. W.(⁶), Chapman S. C.(⁶), Cox P.(⁷), Greve T. R.(⁸), Omont A.(⁹), Frayer D. T.(¹⁰)
Affiliation: (¹)Institut de Radio Astronomie Millimétrique (IRAM), 300 Rue de la Piscine, Domaine Universitaire de Grenoble, St. Martin d'Hères F-38406, France, (²)Max-Planck Institut für extraterrestrische Physik, Giessenbachstrasse Postfach 1312, Garching D-85741, Germany, (³)Department of Physics, University of California at Berkeley, 366 LeConte Hall, Berkeley, CA 94720-7300., (⁴)Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, (⁵)Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, Bonn D-53121, Germany, (⁶)Department of Astronomy, California Institute of Technology, MS 105-24, 1201 East California Boulevard, Pasadena, CA 91125, (⁷)Institut d'Astrophysique Spatiale, Université de Paris Sud, Bâtiment 121, Orsay F-91405, France, (⁸)Institute for Astronomy, Royal Observatory, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK, (⁹)Institut d'Astrophysique de Paris, CNRS, Université de Paris 6, Paris, France, (¹⁰)Space Infrared Telescope Facility Science Center, California Institute of Technology, Mail Code 314-6, Pasadena, CA 91125

Abstract:
We report IRAM millimeter interferometry of three z $\approx 2.4-3.4$Submillimeter Common-User Bolometric Array deep field galaxies. Our CO line observations confirm the rest-frame UV/optical redshifts, thus more than doubling the number of confirmed published redshifts of the faint submillimeter population and proving their high-z nature. In all three sources our measurements of the intrinsic gas and dynamical mass are large ( $10^{10}-10^{11} \mbox{M$_\odot$ }$). In at least two cases the data show that the submillimeter sources are part of an interacting system. Together with recent information gathered in the X-ray, optical, and radio bands, our observations support the interpretation that the submillimeter population, at least the radio-detected ones, consists of gas-rich (gas-to-dynamical mass ratio $\approx 0.5$) and massive interacting starburst/active galactic nucleus systems.

Appeared in : ApJ 597, L113

First Evidence of Dusty Disks around Herbig Be Stars

Fuente A.(¹), Rodríguez-Franco A.(^2,3), Testi L.(⁴), Natta A.(⁴), Bachiller R.(¹), Neri R.(⁵)
(¹)Observatorio Astronómico Nacional, Apartado 1143, E-28800 Alcalá de Henares, Spain, (²)Departamento Matemática Aplicada (Biomatemática), Universidad Complutense de Madrid, Avenida Arcos de Jalón s/n, E-28037 Madrid, Spain, (³)Consejo Superior de Investigaciones Científicas, IEM, DAMIR, Serrano 121, E-28006 Madrid, Spain., (⁴)Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy, (⁵)Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Hères Cedex, France

Abstract:
We have carried out a high-sensitivity search for circumstellar disks around Herbig Be stars in the continuum at 1.4 and 2.7 mm using the IRAM interferometer at the Plateau de Bure. In this Letter, we report data on three well-studied B0 stars: MWC 1080, MWC 137, and R Mon. The two latter have also been observed in the continuum at 0.7 and 1.3 cm using the NRAO Very Large Array. We report the detection of circumstellar disks around MWC 1080 and R Mon with masses of $M_d\approx 0.003$ and $0.01 \mbox{M$_\odot$ }$, respectively, while for MWC 137 we estimate a disk mass upper limit of $0.007 \mbox{M$_\odot$ }$. Our results show that the ratio M_d/M_* is at least an order of magnitude lower in Herbig Be stars than in Herbig Ae and T Tauri stars.

Published in ApJ 598, L39

Gas and dust in the Cloverleaf quasar at redshift 2.5

Weiß  A.(¹), Henkel C.(²), Downes D.(³) and Walter, F.(⁴)
(¹)IRAM, Avenida Divina Pastora 7, 18012 Granada, Spain, (²)MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, (³)IRAM, 300 rue de la Piscine, 38406 St-Martin-d'Hères, France, (⁴)NRAO, PO Box O Socorro, NM, 87801, USA

Abstract:
We observed the upper fine structure line of neutral carbon, $C_{I}({^3P_2} \rightarrow{^3P_1}))$( $\nu_{rest} = 809$GHz), the ¹²CO( $J=3\rightarrow 2$) line ( $\nu_{rest} = 345$ GHz) and the 1.2 mm continuum emission from H1413+117 (Cloverleaf quasar, z=2.5) using the IRAM interferometer. Together with the detection of the lower fine structure line (Barvainis et al. 1997), the Cloverleaf quasar is now only the second extragalactic system, besides M 82, where both carbon lines have convincingly been detected. Our analysis shows that the carbon lines are optically thin and have an excitation temperature of $T_{ex} \approx 30$ K. CO is subthermally excited and the observed line luminosity ratios are consistent with N $(H_2) \approx 10^{3-4}$cm^-3 at T_kin = 30-50 K. Using three independent methods (C_I, dust, CO) we derive a total molecular gas mass (corrected for magnification) of M(H₂ ) $\approx 1.2 \pm 0.3 \times 10^{10}\mbox{M$_\odot$ }$ . Our observations suggest that the molecular disk extends beyond the region seen in CO(7-6) to a zone of more moderately excited molecular gas that dominates the global emission in C_I and the low J CO lines.

Appeared in: A&A 409, L41