- ID:
- ivo://CDS.VizieR/J/A+A/632/A57
- Title:
- G328.2551-0.5321 spectra
- Short Name:
- J/A+A/632/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical hot cores are rich in molecular emission, and they show a high abundance of complex organic molecules (COMs). The emergence of molecular complexity that is represented by COMs, in particular, is poorly constrained in the early evolution of hot cores. We put observational constraints on the physical location of COMs in a resolved high-mass protostellar envelope associated with the G328.2551-0.5321 clump. The protostar is single down to 400au scales and we resolved the envelope structure down to this scale. High angular resolution observations using the Atacama Large Millimeter Array allowed us to resolve the structure of the inner envelope and pin down the emission region of COMs. We use local thermodynamic equilibrium modelling of the available 7.5GHz bandwidth around 345GHz to identify the COMs towards two accretion shocks and a selected position representing the bulk emission of the inner envelope. We quantitatively discuss the derived molecular column densities and abundances towards these positions, and use our line identification to qualitatively compare this to the emission of COMs seen towards the central position, corresponding to the protostar and its accretion disk. We detect emission from 10 COMs, and identify a line of deuterated water (HDO). In addition to methanol (CH_3_OH), methyl formate (CH_3_OCHO) and formamide (HC(O)NH_2_) have the most extended emission. Together with HDO, these molecules are found to be associated with both the accretion shocks and the inner envelope, which has a moderate temperature of Tkin~110K. We find a significant difference in the distribution of COMs. O-bearing COMs, such as ethanol, acetone, and ethylene glycol are almost exclusively found and show a higher abundance towards the accretion shocks with Tkin~180K. Whereas N-bearing COMs with a CN group, such as vinyl and ethyl cyanide peak on the central position, thus the protostar and the accretion disk. The molecular composition is similar towards the two shock positions, while it is significantly different towards the inner envelope, suggesting an increase in abundance of O-bearing COMs towards the accretion shocks. We present the first observational evidence for a large column density of COMs seen towards accretion shocks at the centrifugal barrier at the inner envelope. The overall molecular emission shows increased molecular abundances of COMs towards the accretion shocks compared to the inner envelope. The bulk of the gas from the inner envelope is still at a moderate temperature of Tkin~110K, and we find that the radiatively heated inner region is very compact (<1000au). Since the molecular composition is dominated by that of the accretion shocks and the radiatively heated hot inner region is very compact, we propose this source to be a precursor to a classical, radiatively heated hot core. By imaging the physical location of HDO, we find that it is consistent with an origin within the moderately heated inner envelope, suggesting that it originates from sublimation of ice from the grain surface and its destruction in the vicinity of the heating source has not been efficient yet.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2003
- Title:
- G305 star-forming complex in ^13^CO
- Short Name:
- J/MNRAS/435/2003
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 109-115GHz (3mm) wide-field spectral line observations of ^12^CO, ^13^CO and C^18^O J=1-0 molecular emission and 5.5 and 8.8GHz (6 and 3cm) radio continuum emission towards the high-mass star-forming complex known as G305. The morphology of G305 is dominated by a large evacuated cavity at the centre of the complex driven by clusters of O stars surrounded by molecular gas. Our goals are to determine the physical properties of the molecular environment and reveal the relationship between the molecular and ionized gas and star formation in G305. This is in an effort to characterize the star-forming environment and constrain the star formation history in an attempt to evaluate the impact of high-mass stars on the evolution of the G305 complex. Analysis of CO emission in G305 reveals 156 molecular clumps with the following physical characteristics; excitation temperatures ranging from 7 to 25K, optical depths of 0.2-0.9, H_2_) column densities of 0.1-4.0x10^22^cm^-2^, clump masses ranging from 10^2^ to 10^4^M_{sun}_ and a total molecular mass of >3.5x10^5^M_{sun}_. The 5.5 and 8.8GHz radio continuum emission reveals an extended low surface brightness ionized environment within which we identify 15 large-scale features with a further eight smaller sources projected within these features. By comparing to mid-infrared emission and archival data, we identify nine HII regions, seven compact HII regions, one UC HII region and four extended regions. The total integrated flux of the radio continuum emission at 5.5GHz is ~ 180Jy corresponding to a Lyman continuum output of 2.4x10^50^photons/s. We compare the ionized and molecular environment with optically identified high-mass stars and ongoing star formation, identified from the literature. Analysis of this data set reveals a star formation rate of 0.008-0.016M_{sun}_/yr and efficiency of 7-12%, allows us to probe the star formation history of the region and discuss the impact of high-mass stars on the evolution of G305.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A84
- Title:
- GUAPOS. identified transitions of C2H4O2
- Short Name:
- J/A+A/644/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased spectral survey of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we discuss the detection and relative abundances of the three isomers of C_2_H_4_O_2_: methyl formate, glycolaldehyde, and acetic acid. Observations were carried out with the ALMA interferometer, covering all of band 3 (~32GHz bandwidth) with an angular resolution of 1.2"x1.2" (~4400aux4400au) and a spectral resolution of ~0.488MHz. The transitions of the three molecules have been analyzed with the software XCLASS to determine the physical parameters of the emitted gas. The comparison with chemical models in literature suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both grain-surface reactions and gas-phase chemistry could be able to explain the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A129
- Title:
- GUAPOS II. Identified transitions of molecules
- Short Name:
- J/A+A/653/A129
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present an unbiased spectral survey of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this second paper, we discuss the detection and relative abundances of the peptide-like bond molecules: HNCO, HC(O)NH2, CH_3_NCO, CH_3_C(O)NH_2_, CH_3_NHCHO, CH_3_CH_2_NCO, NH_2_C(O)NH_2_, NH_2_C(O)CN, and HOCH_2_C(O)NH_2_. Observations were carried out with the ALMA interferometer, covering all of band 3 (about 32GHz bandwidth) with an angular resolution of 1.2"x1.2" (about 4400aux4400au) and a spectral resolution of about 0.488MHz. The transitions of the nine molecules have been analyzed with the software MADCUBA to determine the physical parameters of the emitted gas. The results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas-phase through thermal desorption or shock-triggered desorption.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2500
- Title:
- GX 339-4 radio/X-ray flux correlation
- Short Name:
- J/MNRAS/428/2500
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existing radio and X-ray flux correlation for Galactic black holes in the hard and quiescent states relies on a sample which is mostly dominated by two sources (GX 339-4 and V404 Cyg) observed in a single outburst. In this paper, we report on a series of radio and X-ray observations of the recurrent black hole GX 339-4 with the Australia Telescope Compact Array, the Rossi X-ray Timing Explorer and the Swift satellites. With our new long-term campaign, we now have a total of 88 quasi-simultaneous radio and X-ray observations of GX 339-4 during its hard state, covering a total of seven outbursts over a 15-yr period. Our new measurements represent the largest sample for a stellar mass black hole, without any bias from distance uncertainties, over the largest flux variations and down to a level that could be close to quiescence, making GX 339-4 the reference source for comparison with other accreting sources (black holes, neutrons stars, white dwarfs and active galactic nuclei).
- ID:
- ivo://jvo/isas/darts/halca/halca_vsop_correlated_data
- Title:
- HALCA VSOP (the VLBI Space Observatory Programme) Correlated Data
- Short Name:
- HALCA
- Date:
- 19 Oct 2021 07:12:04
- Publisher:
- JVO
- Description:
- The VSOP (VLBI Space Observatory Programme) mission was led by the Institute of Space and Astronautical Science, in collaboration with the National Astronomical Observatory of Japan with international collaboration with NSAS, CSA, JIVE and the world radio telescopes in 14 countries. This mission provided a dedicated space radio telescope "HALCA" launched in February 1997, and carried out high-resolution observations at 1.6, 5.0, and 22 GHz with ground radio observatories to perform Very Long Baseline Interferometry (VLBI) on baselines of up to 2.6 Earth diameters. The observations are continued till 2003, and HALCA finished its operation in 2005.
- ID:
- ivo://CDS.VizieR/VIII/7A
- Title:
- Hat Creek High-Latitude H I Survey
- Short Name:
- VIII/7A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This survey consists of H I 21-cm spectra covering the entire northern sky with absolute Galactic latitude |b|>10 degrees and declination dec>-30degrees. The observations were made with the Hat Creek 85-foot telescope between 1968 and 1970. The individual spectra were obtained with a bank of 100 filters covering the velocity range from -92km/s to +75km/s. The velocity resolution was 2 km/sec (except at the ends of the spectra) and the beamwidth was 36arcmin. The spacing between points observed on the sky is (0.3deg/cosb) in Galactic longitude and (0.6deg) in Galactic latitude. A FITS version of the survey was derived at the Astrophysics Data Facility (NASA/GSFC) from the original catalog of spectra. The approximately 130,000 good spectra in the catalog (i.e., those with status code 1 and which have flat baselines) were interpolated to a uniform channel width in frequency, shifted as appropriate to take into account the proper central velocities, then interpolated onto a regular grid in Galactic coordinates. For the latter interpolation, the cos(b) corrections for longitude offsets were taken into account; no interpolation was done across gaps in coverage greater than 2 deg. Latitude-velocity slices were written in FITS format for each 30 arcmin of longitude. Separate files were written for the negative latitude (b < -10 deg ) and positive latitude (b > 10 deg) ranges. Slices containing no spectra, primarily negative latitude spectra in the fourth Galactic quadrant, were not written. A longitude-latitude map, integrated over all velocities, was also written in FITS format to illustrate the coverage of the individual latitude-velocity slices.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/1910
- Title:
- H-ATLAS NGP LOFAR radio catalogue
- Short Name:
- J/MNRAS/462/1910
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Low-Frequency Array (LOFAR) High-Band Array observations of the Herschel-ATLAS North Galactic Pole survey area. The survey we have carried out, consisting of four pointings covering around 142deg^2^ of sky in the frequency range 126-173MHz, does not provide uniform noise coverage but otherwise is representative of the quality of data to be expected in the planned LOFAR wide-area surveys, and has been reduced using recently developed 'facet calibration' methods at a resolution approaching the full resolution of the data sets (~10x6 arcsec) and an rms off-source noise that ranges from 100{mu}Jy beam^-1^ in the centre of the best fields to around 2mJy/beam at the furthest extent of our imaging. We describe the imaging, cataloguing and source identification processes, and present some initial science results based on a 5{sigma} source catalogue. These include (i) an initial look at the radio/far-infrared correlation at 150 MHz, showing that many Herschel sources are not yet detected by LOFAR; (ii) number counts at 150MHz, including, for the first time, observational constraints on the numbers of star-forming galaxies; (iii) the 150-MHz luminosity functions for active and star-forming galaxies, which agree well with determinations at higher frequencies at low redshift, and show strong redshift evolution of the star-forming population; and (iv) some discussion of the implications of our observations for studies of radio galaxy life cycles.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/136
- Title:
- H{beta} to N2 line fluxes of nearby galaxies
- Short Name:
- J/ApJ/847/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present calibrations for star formation rate (SFR) indicators in the ultraviolet, mid-infrared, and radio-continuum bands, including one of the first direct calibrations of 150MHz as an SFR indicator. Our calibrations utilize 66 nearby star-forming galaxies with Balmer-decrement-corrected H{alpha} luminosities, which span five orders of magnitude in SFR and have absolute magnitudes of -24<M_r_{<}-12. Most of our photometry and spectrophotometry are measured from the same region of each galaxy, and our spectrophotometry has been validated with SDSS photometry, so our random and systematic errors are small relative to the intrinsic scatter seen in SFR indicator calibrations. We find that the Wide-field Infrared Space Explorer W4 (22.8{mu}m), Spitzer 24{mu}m, and 1.4GHz bands have tight correlations with the Balmer-decrement-corrected H{alpha} luminosity, with a scatter of only 0.2dex. Our calibrations are comparable to those from the prior literature for L* galaxies, but for dwarf galaxies, our calibrations can give SFRs that are far greater than those derived from most previous literature.
690. HCG HI-deficiency
- ID:
- ivo://CDS.VizieR/J/A+A/325/473
- Title:
- HCG HI-deficiency
- Short Name:
- J/A+A/325/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present HI observations of 54 Hickson Compact Groups (HCG) of which 41 have been detected in the 21-cm line of neutral hydrogen. For 13 objects upper limits have been obtained. The integrated M_HI_/L_B_ values of the observed HCGs scatter over a large range of values showing strong HI-deficiencies for a great number of objects.
