- ID:
- ivo://CDS.VizieR/J/A+AS/124/205
- Title:
- W3 star-forming region 345 GHz survey
- Short Name:
- J/A+AS/124/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are presented of the 345 GHz spectral survey toward three sources in the W 3 Giant Molecular Cloud: W 3 IRS4, W 3 IRS5 and W 3(H_2_O). Nearly 90% of the atmospheric window between 334 and 365GHz has been scanned using the James Clerk Maxwell Telescope (JCMT) down to a noise level of ~80mK per resolution element. These observations are complemented by a large amount of data in the 230GHz atmospheric window. From this data set physical conditions and beam-averaged column densities are derived for more than 14 chemically different species (over 24 different isotopes). The physical parameters derived in Paper I (Helmich et al., 1994A&A...283..626H) are confirmed by the analysis of the excitation of other species, although there is evidence that the silicon- and sulfur-bearing molecules exist in a somewhat denser and warmer environment. The densities are high, >=10^6^cm^-3^, in the three sources and the kinetic temperatures for the bulk of the gas range from 55K for IRS4 to 220K for W 3(H_2_O). The chemical differences between the three sources are very striking: silicon- and sulfur-bearing molecules such as SiO and SO_2_ are prominent toward IRS5, whereas organic molecules like CH_3_OH, CH_3_OCH_3_ and CH_3_OCHO are at least an order of magnitude more abundant toward W 3(H_2_O). Vibrationally excited molecules are also detected toward this source. Only simple molecules are found toward IRS4. The data provide constraints on the amount of deuterium fractionation and the ionization fraction in the observed regions as well. These chemical characteristics are discussed in the context of an evolutionary sequence, in which IRS5 is the youngest, W 3(H_2_O) somewhat older and IRS4, although still enigmatic, the oldest.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/900/L10
- Title:
- X-band data of the GOTHAM Large Project for TMC-1
- Short Name:
- J/ApJ/900/L10
- Date:
- 15 Feb 2022 11:45:23
- Publisher:
- CDS
- Description:
- We present an overview of the GBT Observations of TMC-1: Hunting Aromatic Molecules Large Program on the Green Bank Telescope. This and a related program were launched to explore the depth and breadth of aromatic chemistry in the interstellar medium at the earliest stages of star formation, following our earlier detection of benzonitrile (c-C6H5CN) in TMC-1. In this work, details of the observations, use of archival data, and data reduction strategies are provided. Using these observations, the interstellar detection of propargyl cyanide (HCCCH2CN) is described, as well as the accompanying laboratory spectroscopy. We discuss these results, and the survey project as a whole, in the context of investigating a previously unexplored reservoir of complex, gas-phase molecules in pre-stellar sources. A series of companion papers describe other new astronomical detections and analyses.
1913. xCOLD GASS catalog
- ID:
- ivo://CDS.VizieR/J/ApJS/233/22
- Title:
- xCOLD GASS catalog
- Short Name:
- J/ApJS/233/22
- Date:
- 02 Nov 2021 07:14:32
- Publisher:
- CDS
- Description:
- We introduce xCOLD GASS, a legacy survey providing a census of molecular gas in the local universe. Building on the original COLD GASS survey, we present here the full sample of 532 galaxies with CO (1-0) measurements from the IRAM 30m telescope. The sample is mass-selected in the redshift interval 0.01<z<0.05 from the Sloan Digital Sky Survey (SDSS) and therefore representative of the local galaxy population with M_*_>10^9^M_{sun}_. The CO (1-0) flux measurements are complemented by observations of the CO (2-1) line with both the IRAM 30 m and APEX telescopes, HI observations from Arecibo, and photometry from SDSS, WISE, and GALEX. Combining the IRAM and APEX data, we find that the ratio of CO (2-1) to CO (1-0) luminosity for integrated measurements is r_21_=0.79+/- 0.03, with no systematic variations across the sample. The CO (1-0) luminosity function is constructed and best fit with a Schechter function with parameters L_CO_^* ^=(7.77+/-2.11)x10^9^K.(km/s).pc^2^, {phi}^*^=(9.84+/-5.41)x10^-4^Mpc^-3^, and {alpha}=-1.19+/-0.05. With the sample now complete down to stellar masses of 10^9^M_{sun}_, we are able to extend our study of gas scaling relations and confirm that both molecular gas fractions (f_H2_) and depletion timescale (t_dep_(H2)) vary with specific star formation rate (or offset from the star formation main sequence) much more strongly than they depend on stellar mass. Comparing the xCOLD GASS results with outputs from hydrodynamic and semianalytic models, we highlight the constraining power of cold gas scaling relations on models of galaxy formation.
- ID:
- ivo://CDS.VizieR/J/A+A/471/1105
- Title:
- XMM-LSS at 240MHz and 610MHz
- Short Name:
- J/A+A/471/1105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The low-frequency radio survey of the XMM-Large Scale Structure (XMM-LSS) field aims to study the connection between the extragalactic radio source populations and their environment as traced by X-ray and optical emission. In this paper we present new radio observations of the XMM-LSS field carried out using the Giant Meterwave Radio Telescope at 240 and 610MHz. These observations complement the observations presented by Cohen at al. (2003, Cat. <J/ApJ/591/640>) and Tasse et al. (2006, Cat. <J/A+A/456/791>) at 74 and 325MHz with the Very Large Array. At 240 and 610MHz, we reach noise levels of ~2.5 and ~0.3mJy/beam, leading to the detection of 466 and 769 sources over 18.0 and 12.7 degree^2^ with resolutions of 14.7arcsec and 6.5arcsec respectively. Combining these data with the available source lists at 74, 325 (Tasse et al., 2006, Cat. <J/A+A/456/791>) and 1400MHz (NVSS), we build a multifrequency catalogue containing 1611 radio sources. We check for consistency of the astrometry and flux density estimates. We fit a simple synchrotron radiation model to the flux density measurements of the 318 radio sources being detected in at least 4 bands. While ~26% of them show signature of spectral ageing, ~6% show self absorption.
- ID:
- ivo://CDS.VizieR/J/A+A/456/791
- Title:
- XMM-LSS field at 74 and 325MHz
- Short Name:
- J/A+A/456/791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM Large Scale Structure survey (XMM-LSS) is an X-ray survey aimed at studying the large scale structure of the Universe. The XMM-LSS field is currently being followed up using observations across a wide range of wavelengths, and in this paper we present the observational results of a low frequency radio survey of the XMM-LSS field using the Very Large Array at 74 and 325MHz. This survey will map out the locations of the extragalactic radio sources relative to the large scale structure as traced by the X-ray emission. This is of particular interest because radio galaxies and radio loud AGN show strong and complex interactions with their small and larger scale environment, and different classes of radio galaxies are suggested to lie at different places with respect to the large scale structure.
- ID:
- ivo://CDS.VizieR/J/A+A/490/879
- Title:
- XMM-LSS field optical identifications
- Short Name:
- J/A+A/490/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM-Large Scale Structure survey field (XMM-LSS) is an extragalactic window surveyed in the X-ray with the XMM-Newton satellite. It has also been observed in the optical with the Canada-France Hawaii Telescope (CFHTLS survey), and in the infrared with the Spitzer Space Telescope (SWIRE survey). These surveys have been carried out to study the structure and evolution of both baryonic and dark matter on cosmological scales. In two previous papers, we presented deep low frequency radio surveys of the XMM-LSS field, with limiting flux density levels of ~4 and ~1.5mJy/beam at 325 and 610MHz respectively (5{sigma}). These radio surveys were motivated by the need to understand the various connections between the host galaxies of radio sources and their environments. In this paper, we identify optical counterparts to the low frequency radio sources, using the CFHTLS optical catalogue and images, that have an i-band limiting magnitude of i_AB_~25.
- ID:
- ivo://CDS.VizieR/J/ApJ/591/640
- Title:
- XMM-LSS low-frequency radio counterparts
- Short Name:
- J/ApJ/591/640
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM Large-Scale Structure Survey (XMM-LSS) is a major project to map the large-scale structure of the universe out to cosmological distances. An 8x8 region will be surveyed by XMM with planned optical follow-up to produce a three-dimensional map of many hundreds of clusters out to a redshift of z=1. To explore the relation of the large-scale structure to the location and properties of extragalactic radio sources, the XMM-LSS project also includes a low-frequency radio survey of this region. This combination will provide unprecedented insight into how the radio source formation and evolution are affected by the local environment. Here we present preliminary results from our 325 and 74MHz surveys in this region. At 325MHz, we have a flux limit of 4mJy/beam, a resolution of 6.3", and a total of 256 source detections over 5.6deg^2^. At 74MHz, we have a flux limit of 275mJy/beam, a resolution of 30", and a total of 211 source detections over 110deg^2^. We describe these results and explore what they tell us about the population of extragalactic low-frequency radio sources. The 74MHz survey represents the first presentation of a deep, subarcminute resolution survey at such a low frequency. This was made possible by recent advances in both hardware and data reduction algorithms, which we describe in detail.
- ID:
- ivo://CDS.VizieR/J/MNRAS/352/91
- Title:
- XMM-Newton/2dF survey. IV.
- Short Name:
- J/MNRAS/352/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the X-ray spectral properties of 61 hard X-ray (2-8keV) selected sources from the bright XMM-Newton/2dF (f(2-8keV)>10^-14^erg/cm^2^/s) survey. This comprises nine XMMNewton pointings in the North Galactic Pole region (~1.6deg^2^) and overlaps with the SDSS, 2QZ and 2dFGRS surveys. Our sources contribute about 50 per cent of the 2-10keV X-ray background down to the flux limit of 10^-14^erg/cm^2^/s. The hardness ratio distribution of the sample suggests a deficit of heavily absorbed sources. Spectroscopic identifications exist for 34 sources.
- ID:
- ivo://CDS.VizieR/J/A+A/281/355
- Title:
- X-ray AGN content of Molonglo 408MHz survey
- Short Name:
- J/A+A/281/355
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cross-correlation of a source list from the ROSAT All-Sky Survey with the Molonglo 408MHz survey (MRC) yields to a catalogue of 549 sources. The majority of the objects are quasars and radio galaxies with known optical counterparts; more than one third of the objects are optically unidentified.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A66
- Title:
- X-ray and radio emission of type 1 AGNs
- Short Name:
- J/A+A/545/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray emission from Active Galactic Nuclei (AGN) is dominated by the accretion disk around a supermassive black hole. The radio luminosity, however, has not such a clear origin except in the most powerful sources where jets are evident. The origin (and even the very existence) of the local bi-modal distribution in radio-loudness is also a debated issue. By analysing X-ray, optical and radio properties of a large sample of type 1 AGN and quasars (QSOs) up to z>2, where the bulk of this population resides, we aim to explore the interplay between radio and X-ray emission in AGN, in order to further our knowledge on the origin of radio emission, and its relation to accretion. We analyse a large (~800 sources) sample of type 1 AGN and QSOs selected from the 2XMMi XMM-Newton X-ray source catalogue, cross-correlated with the SDSS DR7 spectroscopic catalogue, covering a redshift range from z~0.3 to z~2.3. Supermassive black hole masses are estimated from the Mg II emission line, bolometric luminosities from the X-ray data, and radio emission or upper limits from the FIRST catalogue. Most of the sources accrete close to the Eddington limit and the distribution in radio-loudness does not appear to have a bi-modal behaviour. We confirm that radio-loud AGN are also X-ray loud, with an X-ray-to-optical ratio up to twice that of radio-quiet objects, even excluding the most extreme strongly jetted sources. By analysing complementary radio-selected control samples, we find evidence that these conclusions are not an effect of the X-ray selection, but are likely a property of the dominant QSO population. Our findings are best interpreted in a context where radio emission in AGN, with the exception of a minority of beamed sources, arises from very close to the accretion disk and is therefore heavily linked to X-ray emission. We also speculate that the radio-loud/radio-quiet dichotomy might either be an evolutionary effect that developed well after the QSO peak epoch, or an effect of incompleteness in small samples.
