Scientific results in press

Jets and high-velocity bullets in the Orion A outflows. Is the IRc2 outflow powered by a variable jet

A. Rodríguez-Franco(^1,2), J. Martín-Pintado(²), and T.L. Wilson(^3,4)
(¹)Departamento de Matemática Aplicada$\,$II, Sección departamental de Optica, Escuela Universitaria de Optica, Universidad Complutense de Madrid. Av. Arcos de Jalón s/n. E-28037 Madrid, Spain
(²)Observatorio Astronómico Nacional (IGN), Campus Universitario, Apdo. 1143, E-28800, Alcalá de Henares, Spain
(³)Max Planck Institut für Radioastronomie, Postfach 2024, D-53010 Bonn, Germany.
(⁴)Sub-mm Telescope Observatory, Steward Observatory, The University of Arizona, Tucson, Az, 85721.

Abstract: We present high sensitivity maps of the High Velocity (HV) CO emission toward the molecular outflows around IRc2 and Orion-S in the Orion A molecular cloud. The maps reveal the presence of HV bullets in both outflows with velocities between 40-80$\,$km$\,$s^-1 from the ambient gas velocity. The blue and redshifted CO HV bullets associated with the IRc2 outflow are distributed in thin (12''-20'', $0.02-0.04\,$pc) elliptical ring-like structures with a size of $\sim10''\times50''$ ( $0.02\times0.1\,$pc). The CO emission at the most extreme blue and redshifted velocities (EHV) peaks 20'' north of source I, just inside the rings of the HV bullets. The low velocity H₂O masers and the H₂^* bullets around IRc2 are located at the inner edges of the ring of CO HV bullets and surrounding the EHV CO emission. Furthermore, the high velocity H₂O masers are very well correlated with the EHV CO emission. This morphology is consistent with a model of a jet driven molecular outflow oriented close to the line of sight.

In the Orion-S outflow, the morphology of the CO HV bullets shows a bipolar structure in the southeast $\leftrightarrow$northwest direction, and the H₂O masers are found only at low velocities in the region between the exciting source and the CO HV bullets.

The morphology of the CO HV bullets, the radial velocities and the spatial distribution of the H₂O masers in both outflows, as well as the H₂^* features around IRc2, are consistent with a model in which these outflows are driven by a jet variable in direction. In this scenario, the large traverse velocity measured for the H₂O masers in the IRc2 outflow, $\sim18\,$km$\,$s^-1, supports the evolutionary connection between the jet and the shell-like outflows.

Astronomy & Astrophysics Letters , in press; preprint requests: arturo@oan.es or on the Web:
http://www.oan.es/preprints/lista.html

Bipolar Molecular Outflows

Rafael Bachiller and Mario Tafalla(¹)
(¹) Observatorio Astronómico Nacional (IGN), Campus Universitario, Apdo. 1143, E-28800, Alcalá de Henares, Spain


Abstract: Molecular outflows have been known to exist for about 20 years, and during these two decades they have been the subject of a very intense research effort. Outflows seem to play a major role in all the stages of star formation, from providing a mechanism for angular momentum loss to allow the assembling of the protostar, to stopping gravitational collapse and fixing the central object mass, and to dispersing the star-forming dense core and revealing the newly born star. In this chapter, we review the current knowledge on bipolar molecular outflows, with emphasis on those from low-mass young stars and protostars. We compare the properties of the poorly collimated outflows (which we refer as ``classical'') with those of a recently identified population of highly collimated flows. We propose that the observed differences are due to outflow evolution, and discuss how outflows evolve with time. We also review the extraordinary chemical anomalies found in some extremely young outflows, and the current models of outflow acceleration. We attempt to review not just those properties well understood, but point out future directions on outflow research.

To appear in The Physics of Star Formation and Early Stellar Evolution ed. C.J. Lada, (Kluwer, Dordrecht). Preprints available at:
http://www.oan.es/preprints/lista.html

A Molecular Counterpart to the HH 1-2 Optical System

Amaya Moro-Martín(¹), & José Cernicharo(¹), Alberto Noriega-Crespo(²), Jesús Martín-Pintado(³)
(¹)Instituto de Estructura de la Materia, Dpto. de Fisica Molecular, CSIC, Serrano 121, E-28006 Madrid, Spain
(²)Infrared Processing and Analysis Center, CalTech-JPL, Pasadena, CA 91125, USA
(³)Observatorio Astronómico Nacional. Apartado 1143, E-28800 Alcalá de Henares. Spain

Abstract: We present high angular resolution and sensitivity ¹²CO and ¹³CO J = 2-1 and J = 1-0 observations of the HH 1-2 outflow taken with then 30-m IRAM radio telescope. The observations show the bipolar molecular counterpart of the optical system driven by the VLA 1 embedded source moving with a velocity of $\simeq$ 30 km s^-1. Along the optical jet there are certain regions where the molecular gas reaches deprojected velocities of 100 km s^-1, and that we interpret as the molecular ¹²CO jet. The bipolar CO outflow has a length of $\sim 260\mbox{$''$ }$ and a curved morphology towards the North where it extends further away than the HH1 object ($\simeq$ 120 $\mbox{$''$ }$) .

Two new molecular outflows have been detected, one arising from IRAS 05339-0647 which excites the HH 147 optical flow and another powered by VLA 2 which drives the HH 144 optical outflow. The molecular outflow driven by the VLA 3 source is also clearly detected and spatially resolved from the VLA 1 main outflow.

Astrophysical Journal Letters in press. Preprints available: cerni@astro.iem.csic.es

GG Tau: the Ring World

S.Guilloteau(¹) - A.Dutrey(¹) - M.Simon(²)
(¹) Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France
(²)Dept. of Physics and Astronomy, State Univ. of New York, Stony Brook NY 11794-3800, USA

Abstract: We present sub-arcsecond images of the mm dust emission and ¹³CO J=2-1 line emission in the young quadruple system GGTau (see cover picture). These observations unambiguously resolve the circumbinary disk of the close ( $\sim 0.3''$) binary system into two distinct components: an extremely dense, sharp-edged ring, surrounded by an extended disk. Continuum emission is also detected from the center of this structure; it probably arises in the small circumstellar disk or disks of the binary. The kinematic data show that the ring+disk system is in Keplerian rotation and yield the estimate $M = (1.28 \pm 0.07)(D/140\,\mathrm{pc}) \hbox{M$_\odot$ }$ for the mass of the binary stars. We derive the physical parameters of the ring and disk from these data and from new 2'' resolution images of the HCO⁺ J=1-0 line and 3.4mm continuum emission. The temperature in the ring plus disk system is consistent with heating by the stellar light (including the IR excess coming from the inner disks). Comparison with the optical/NIR images indicates a disk thickness compatible with an hydrostatic equilibrium.

Astronomy & Astrophysics in press; preprints: guillotte@iram.f

Los Planetas recogen todos sus singles en un disco doble

Planets gather all their singles in a double disk

Abstract: Los planetas han echado la vista atras a 7 años de carrera y han recogido en una especie de album de memorias 33 temas publicados hasta ahora sólo en singles y epés. Segun Florent Muñoz del grupo granadino, el disco doble se titula Compositiones para una orchestra quimica.

El Pais, May 4, 1999, Espectaculos.

Interferometric observations of nearby galaxies

N. Neininger(¹)
(¹) Radioastronomisches Institut der Universtät Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany

Abstract: The IRAM Plateau de Bure interferometer is presently the most sensitive telescope in the range of 80-250 GHz. For the study of nearby galaxies, the field of view can be enlarged and the medium-small spacings recovered with the help of mosaicking techniques. This is particularly useful for the study of narrow spiral arms and edge-on galaxies.

  

Figure: Selected velocity channel maps of the ¹²CO(1-0) emission in NGC2146. The level step is 60mJy/beam and the systemic velocity is subtracted. The cross marks the center of the galaxy. The traces of an outflow are clearly visible at all but the extreme velocity-channels.

NGC2146

NGC2146, the ``dusty hand'' galaxy features a system of three dust lanes (spiral arms?) and clear signs of a starburst. It is seen with a large inclination angle. In contrast to other galaxies with strong star formation activity like M82 or NGC3628, no companion is visible that could have triggered the activity and there is no obvious sign of a present close encounter or merger. It is generally believed that the starburst was triggered by a merger which took place long ago and has disturbed the dynamics of the interstellar gas. The aim of our study was to search for traces of such a disturbance.

  

Figure: The integrated intensity of the ¹²CO(1-0) emission of NGC2146, the steps are 5Jy/beam$\cdot$kms^-1. It peaks towards the central region, where also the strongest radio point sources are found. Note also the warp already prominent at this small scale.

We (N. Neininger, A. Greve, A. Tarchi) mapped NGC2146's central 4 kpc region with the IRAM interferometer in the ¹²CO (1-0), (2-1) and the ¹³CO(1-0) lines. Although the emission is found to be mostly concentrated towards the center, like in many spirals, a warp is clearly visible (Fig. 5, right part). We see outflowing molecular gas, but no evidence of gas linked to a merger or a companion galaxy (see Fig. 3).

Parallel to these observations of the molecular gas content, we have obtained high-resolution data at radio wavelengths ($\lambda$ 6 and 20 cm) with a combination of MERLIN and the VLA. We could identify a number of point sources which are currently under investigation (Tarchi et al., in preparation). The hope is to eventually compare their properties with their counterparts in M82.

M31

  

Figure: Maps of two prominent neaby cloud complexes of M31: D 84 (left) and D 47 (right). The panels marked with a number (units kms^-1) show the intensity distribution in 10 kms^-1-wide velocity channels centred at selected velocities; the panels marked `INT' display the velocity-integrated intensity. Contours are spaced in 10% steps of the peak which is $\sim\!1$Jy/beam for the channel maps, 2.5Jy/beam for the integrated map of D84, and 1.6Jy/beam for that of D 47. Note the filamentary shape and multi-component structure of cloud complex D 47.

The molecular gas in the southern half of M 31 is mostly concentrated in bright cloud associations distributed along in 3 narrow spiral arms of radius $\sim 6,\, 11$ and 18 kpc (Neininger et al. 1998). Figure 6 shows two such complexes observed at a resolution of $\simeq 2''$ (10 pc) with the IRAM interferometer. The molecular complex D 84 lies in a quiescent part of the 11 kpc arm, while D 47 is located 1.5 kpc farther to the SW, at the edge of one of the brightest HII regions of M 31. CO emission in D 84 mostly arises from a compact, 50-pc diameter source with a narrow velocity span (20 kms^-1); D 47 shows a complex filamentary structure with multiple velocity components. The spectra at the border of the bright HII region show two velocity components of similar intensities, spaced by 40 km^-1: emission is visible at positions (0,0) and (-20,-20) at -448 kms^-1 and -484 kms^-1 (LSR), but not at -461 kms^-1.

Such two-component spectra would be difficult to interpret in the Milky Way, where they would be attributed to two components at very different places along the line of sight. Here, it is clear from the location and the separation of the spiral arms that both belong to one single cloud complex. But wherefrom originate such big differences between those relatively close neighbours? The answer lies probably in the proximity of D 47 to the bright and extended HII region. Similarly broad spectra are found in the big southern dark cloud D 39 which also hosts a bright HII region and several star clusters. These are only few examples, but they point all into the same direction: broad or multiple-component spectra are most likely caused by local effects. These cloud complexes are certainly not virialized on the scale of 100pc, the resolution of the 30-m telescope at the distance of M31. The determination of the gas mass on the basis of data from the two instruments yields grossly differing values. To further investigate the properties of the molecular cloud complexes in M31, we (N. Neininger, M. Guélin, R. Lucas et al.) are enlarging our sample of combined studies with the two IRAM instruments while pushing the angular resolution well below the 10pc limit with the PdBI.

Hodge P.W., 1981, Atlas of the Andromeda Galaxy University of Washington Press
Neininger N., Guélin M., Ungerechts H., Lucas R., Wielebinski, R., 1998a, ``Carbon Monoxide Emission as a Precise Tracer of Molecular Gas in the Andromeda Galaxy'' Nature 395, 871-873

Proceedings of the 3rd Cologne-Zermatt Symposium in press; preprints: nneini@astro.uni-bonn.de

Evidence for an Expanding Molecular Superbubble in M82

A. Weiß, F. Walter, N. Neininger and U. Klein(¹)
(¹)Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany

Abstract: We present evidence for an expanding superbubble in M82 (diameter: $\sim 130$ pc, expansion velocity: $\sim 45$ kms^-1, mass $\sim 8\cdot10^6$ M$_\odot$) as traced by ¹²CO(1-0), ¹²CO(2-1), ¹³CO(1-0) and C¹⁸O(1-0) observations. The superbubble is centred around the most powerful supernova remnant 41.9+58 in M82. The CO observations show that the molecular superbubble already broke out of M82's disk. This scenario is supported by ROSAT HRI observations which suggest that hot coronal gas originating from inside the shell is the main contributor to the diffuse X-ray outflow in M82. We briefly discuss observations of the same region at other wavelengths (radio continuum, optical, H I, X-rays, ionized gas). From our spectral line observations, we derive a kinematic age of about 10⁶ years for the superbubble. Using simple theoretical models, the total energy needed for the creation of this superbubble is of order $2\times 10^{54}$ ergs (energy equivalent of 100 `regular' type II supernova (SN) explosions and the strong stellar winds of their progenitors). The average energy input rate (0.001 SN yr^-1) is reasonable given the high SN rate of $\sim 0.1$ SN yr^-1 in the central part of M82. As much as 10% of the energy needed to create the superbubble is still present in form of the kinematic energy of the expanding molecular shell. This newly detected expanding molecular superbubble is believed to be powered by the same objects which also lie at the origin of the prominent X-ray outflow in M82. It can therefore be used as an alternative tool to investigate the physical properties of these sources.

Astron. Astrophysics Letter, in press

Intergalactic cold dust in the NGC4631 group

N. Neininger(^1,2) and M. Dumke(^2,3)
(¹)Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
(²)Institut de Radioastronomie Millimétrique, 300, rue de la piscine, F-38406 St.Martin d'Hères, France
(³)Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

Abstract: For the first time, we have detected extraplanar cold dust at distances out to more than 10kpc, situated in the halo of the interacting galaxy NGC4631. The dust emission disk is much thinner than the warped HI disk and new structures emerge. In particular, a giant arc has been found that is linked to anomalies in the kinematical structure of the atomic gas. Most of the extraplanar dust is closely associated with HI spurs that have been found earlier. These spurs obviously are traces of the interaction. The dust emission within the plane reaches the border of the optical disk.

The activity of the disk of NGC4631 is moderately enhanced by the interaction, but no gas moving in the z-direction could be found. Hence it seems unlikely that strong winds have deposited the high-zdust. Instead, the coincidence with the HI features suggests that we see a track left behind by the interaction. In addition, the HI shows a supershell formed by an impact in the zone where the dust trail crosses the disk. This region is also characterized by disturbances in the distribution of the H$\alpha$ light. The masses associated with the dust can be estimated only very roughly on the basis of the existing data; they are of the order of a few 10⁹M$_\odot$ of gas.

  

Figure 7: Map of the 1.2mm emission of NGC4631, overlaid on an image taken from the Digital Sky Survey. The levels are -6 (dotted), 6, 11, 21, 41, 81 mJy/beam. Only significant emission is shown and the outer parts of the map with higher noise have been cut off. The small object north of the disk is the dwarf elliptical galaxy NGC4627; the other companion, NGC4656, is situated about half a degree away in the south-east.

Publications of the National Academy of Sciences (USA), in press

Extended warm CO gas in three nearby galaxies

R. Wielebinski(¹), M. Dumke(²), and Ch. Nieten(¹)
(¹) Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
(²) Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères, France

Abstract:

  

Figure: CO(3-2) spectra in M51, with positions relative to the central coordinates ${\rm R.A.[1950]} = 13^{\rm h}27^{\rm m}46^{\rm s}\!\!.1$, ${\rm Dec.[1950]} = 47^{\circ}27'14''$. The scale of the individual spectra is $v_{\rm lsr} = 250 - 590\,{\rm km/s}$, $T_{\rm mb} = -0.2 - 0.8\,{\rm K}$.

We report the detection of distributed CO(3-2) line emission in nearby normal galaxies. The CO gas is a well-known tracer of physical conditions in the emitting regions. The line transitions from higher energy levels (the J=3 level is 33K above ground) are indicators of the presence of warm and dense gas. Until now this warm gas has been studied only in the nuclei of starburst galaxies. Using the Heinrich-Hertz-Telescope on Mt. Graham we were able to detect extended CO(3-2) line emission in more than ten normal galaxies. In a first paper we present the results for the three galaxies M51 (Fig. 8), NGC278 and NGC4631. In particular, we compare our results with observations of the lower CO line transitions made with radio telescopes of similar angular resolution.

Astronomy & Astrophysics in press; preprints: dumke@iram.fr

Dust and CO lines in high redshift quasars

S. Guilloteau (¹), A. Omont (²), P. Cox (³), R.G. McMahon (⁴) and P. Petitjean (²)
(¹) IRAM, 300 rue de la Piscine, F-38406 Saint Martin d'Hères Cedex
(²)Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago, F-75014 Paris
(³) Institut d'Astrophysique Spatiale, Université Paris XI, F-91405 Orsay Cedex
(⁴) Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, U.K.

Abstract: We report the results of a systematic search for redshifted rotational lines of CO and dust emission towards a sample of 9 high redshift radio quiet quasars using the IRAM Plateau de Bure interferometer. Dust emission at $\sim 1.35$ mm has been found in 5 out of the 9 objects. These results confirm the corresponding previous detections with the MPIfR bolometer at the 30-m. No 3mm continuum was detected in any source. The flux densities measured at 1.35 mm with the interferometer are systematically smaller by $\sim 30 \%$from the broad-band bolometer fluxes, consistent with an average spectral index of $\sim 3.5$ within the calibration uncertainty.

In parallel, searches for CO in significant redshift ranges were performed for 8 of the above sources. 6 sources were not detected. Assuming a line width of $\leq 450$km.s^-1, we obtain typical upper limits of $\sim 0.4 - 0.5$ Jykm.s^-1 at the $3 \sigma$ level in the frequency (redshift) range searched. We report a tentative ($3 \sigma$) detection of the J=3-2 line of CO in Q 1230+1627B, and a unambigous detection of the J=5-4 CO line in the gravitationally lensed radio quiet quasar BRI 0952-0115 at a redshift of z=4.43. After BR 1202-0725 at z=4.69 (Otha et al. 1996, Omont et al. 1996a), and BRI 1335-0417 at z=4.41(Guilloteau et al. 1997), this is the third detection of CO at z>4. The velocity-integrated CO(J=5-4) line flux is $\rm0.91 \pm 0.11 \,Jy \, km \,s^{-1}$, with a linewidth of $\rm 230 \pm 30 \, km \, s^{-1}$. The 1.35 mm (250 $\rm\mu m$ rest wavelength) dust continuum flux density is 2.23$\pm$0.51 mJy, in agreement with previous measurements at 1.25 mm at the 30-m IRAM telescope. The ratio of the CO to 1.35 mm continuum flux is comparable to that of BRI 1335-0417 and 2-3 times larger than for BR 1202-0725. The angular resolution of the observation is not high enough to give evidence of any extension of the 1.35mm continuum and 3mm CO emission.

Astronomy & Astrophysics in press; preprints: guillote@iram.fr

 

Figure 9: The CO(J=5-4) line observed in the radio quiet quasar BRI 0952-0115 with the IRAM interferometer