- ID:
- ivo://CDS.VizieR/J/A+A/638/A105
- Title:
- 8 massive proto-cluster clumps NH2D & NH3 cubes
- Short Name:
- J/A+A/638/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial stage of star formation is very difficult to study because of its high density (n_H_2> 10^6^cm^-3^) and low temperature (T_dust_<18K). Under such conditions, many molecules become depleted from the gas phase by freezing out onto dust grains. However, the deuterated species could remain gaseous under these extreme conditions and are thus ideal tracers. We investigate the gas dynamics and NH_2_D chemistry in eight massive pre/protocluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71). We present NH_2_D 1_11-1_01 (at 85.926GHz), NH_3_ (1,1) and (2,2) observations in the eight clumps using the PdBI and the VLA, respectively. We use 3D GAUSSCLUMPS to extract NH_2_D cores and provide a statistical view of their deuterium chemistry. We use NH_3_ (1,1) and (2,2) data to investigate the temperature and dynamics of dense and cold objects. We find that the distribution between deuterium fractionation and kinetic temperature shows a number density peak at around T_kin_=16.1K, and the NH_2_D cores are mainly located at a temperature range of 13.0 to 22.0K. The 3.5mm continuum cores have a kinetic temperature with the median width of 22.1+/-4.3K, which is obviously higher than the temperature in NH_2_D cores. We detect seven extremely high deuterium fractionation of 1.0<=D_frac_<=1.41. We find that the NH_2_D emission does not appear to coincide exactly with either dust continuum or NH3 peak positions, but often surrounds the star-formation active regions. This suggests that the NH_2_D has been destroyed by the central young stellar object (YSO) due to its heating. The detected NH_2_D lines are very narrow with a median width of 0.98+/-0.02km/s, which is dominated by non-thermal broadening. The extracted NH_2_D cores are gravitationally bound ({alpha}_vir_<1), are likely prestellar or starless, and can potentially form intermediate-mass or high-mass stars in future. Using NH3 (1,1) as a dynamical tracer, we find very complicated dynamical movement in all the eight clumps, which can be explained by a combined process with outflow, rotation, convergent flow, collision, large velocity gradient, and rotating toroids. High deuterium fractionation strongly depends on the temperature condition. NH_2_D is a poor evolutionary indicator of high-mass star formation in evolved stages, but a useful tracer in the starless and prestellar cores.
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- ID:
- ivo://CDS.VizieR/J/A+A/627/A85
- Title:
- 8 massive proto-cluster clumps observations
- Short Name:
- J/A+A/627/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby HII regions. We present a high angular resolution study of a sample of 8 massive proto-cluster clumps. Combining infrared data, we use few-arcsecond resolution radio- and millimeter interferometric data to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring HII regions. Taking advantage of that, we test triggered star formation using a novel method where we study the alignment of the centres of mass traced by dust emission at multiple scales. The eight massive clumps have masses ranging from 228 to 2279M_{sun}_. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff~0.02pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8M_{sun}_ at small scale of Reff~0.02pc. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1pc). We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.
- ID:
- ivo://CDS.VizieR/VII/2A
- Title:
- Master list of radio sources, updated 1978
- Short Name:
- VII/2A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Master List of Radio Sources (MSL) has been prepared by combining about thirty catalogues in a common format. Approcimately 25000 listings are included for some 12000 separate sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/148
- Title:
- 2MASX/NVSS galaxies brighter than K_20fe_=12.25
- Short Name:
- J/ApJ/872/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 15658 NRAO VLA Sky Survey (NVSS) radio sources among the 55288 2 Micron All-Sky Survey eXtended (2MASX) galaxies brighter than k_20fe_=12.25 at {lambda}=2.16{mu}m and covering the {Omega}=7.016sr of sky defined by J2000 {delta}>-40{deg} and |b|>20{deg}. The complete sample of 15043 galaxies with 1.4GHz flux densities S>=2.45mJy contains a 99.9% spectroscopically complete subsample of 9517 galaxies with k_20fe_<=11.75. We used only radio and infrared data to quantitatively distinguish radio sources powered primarily by recent star formation from those powered by active galactic nuclei. The radio sources with log[L(W/Hz)]>19.3 that we used to derive the local spectral luminosity and power-density functions account for >99% of the total 1.4GHz spectral power densities U_SF_=(1.54+/-0.20)x10^19^W/Hz/Mpc^3^ and U_AGN_=(4.23+/-0.78)x10^19^W/Hz/Mpc^3^ in the universe today, and the spectroscopic subsample is large enough that the quoted errors are dominated by cosmic variance. The recent comoving star formation rate density indicated by USF is {psi}~0.015M_{sun}_/yr/Mpc^3^.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/73
- Title:
- MAVERIC survey: deep VLA imaging of 25 GCs
- Short Name:
- J/ApJ/903/73
- Date:
- 17 Feb 2022 13:24:49
- Publisher:
- CDS
- Description:
- The MAVERIC survey is the first deep radio continuum imaging survey of Milky Way globular clusters, with a central goal of finding and classifying accreting compact binaries, including stellar-mass black holes. Here we present radio source catalogs for 25 clusters with ultra-deep Karl G. Jansky Very Large Array observations. The median observing time was 10 hr per cluster, resulting in typical rms sensitivities of 2.3 and 2.1{mu}Jy per beam at central frequencies of 5.0 and 7.2GHz, respectively. We detect nearly 1300 sources in our survey at 5{sigma}, and while many of these are likely to be background sources, we also find strong evidence for an excess of radio sources in some clusters. The radio spectral index distribution of sources in the cluster cores differs from the background, and shows a bimodal distribution. We tentatively classify the steep-spectrum sources (those much brighter at 5.0GHz) as millisecond pulsars and the flat-spectrum sources as compact or other kinds of binaries. These provisional classifications will be solidified with the future addition of X-ray and optical data. The outer regions of our images represent a deep, relatively wide-field (~0.4deg^2^) and high-resolution C band background survey, and we present source counts calculated for this area. We also release radio continuum images for these 25 clusters to the community.
- ID:
- ivo://CDS.VizieR/J/A+AS/134/115
- Title:
- Medicina 6.7GHz methanol masers survey
- Short Name:
- J/A+AS/134/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table2 contains the name of the sources and their coordinates (1950) observed, but not detected, with the Medicina Radiotelescope at 6.7GHz in 1995, March. Source are associated with one or more type of phenomena typical of star forming regions (see note 1 for code description). The number of non detected sources is 387.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/39
- Title:
- Merging galaxy cluster deep observations
- Short Name:
- J/ApJS/240/39
- Date:
- 18 Jan 2022 14:59:05
- Publisher:
- CDS
- Description:
- Multi-band photometric and multi-object spectroscopic surveys of merging galaxy clusters allow for the characterization of the distributions of constituent DM and galaxy populations, constraints on the dynamics of the merging subclusters, and an understanding of galaxy evolution of member galaxies. We present deep photometric observations from Subaru/SuprimeCam and a catalog of 4431 spectroscopic galaxies from Keck/DEIMOS observations of 29 merging galaxy clusters ranging in redshift from z=0.07 to 0.55. The ensemble is compiled based on the presence of radio relics, which highlight cluster-scale collisionless shocks in the intracluster medium. Together with the spectroscopic and photometric information, the velocities, timescales, and geometries of the respective merging events may be tightly constrained. In this preliminary analysis, the velocity distributions of 28 of the 29 clusters are shown to be well fit by single Gaussians. This indicates that radio-relic mergers largely occur transverse to the line of sight and/or near-apocenter. In this paper, we present our optical and spectroscopic surveys, preliminary results, and a discussion of the value of radio-relic mergers for developing accurate dynamical models of each system.
- ID:
- ivo://CDS.VizieR/B/avo.rad
- Title:
- MERLIN+VLA images of HDF/HFF sources
- Short Name:
- B/avo.rad
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 18 days of MERLIN data and 42 hours of A-array VLA data at 1.4 GHz have been combined to image a 10 arcminute field centred on the Hubble Deep Field. This area includes both the Hubble Deep and Flanking Fields. A complete sample of 92 sources with flux densities above 40µJy have been detected using the VLA data, and imaged with the MERLIN+VLA combination at resolutions of 0.2, 0.3 and 0.5 arcsecond. These are the most sensitive 1.4 GHz images yet made, with rms noise levels of 3.3µJy/beam in the 0.2 arcsecond images. Virtually all the objects are resolved by the MERLIN+VLA combination images showing that they have angular sizes in the range 0.2 to 3 arcseconds, typically smaller than the sizes of the optical galaxy images. In addition to the imaging of 92 sources found with the VLA alone, the central 3 arcminutes, which encloses the HDF, has been separately imaged with the MERLIN+VLA combination at the full 3.3µJy/beam sensitivity to search for compact sources fainter than 40µJy. No additional sources were found that were not previously detected by the VLA, indicating that such sources are heavily resolved with MERLIN and hence must have typical angular sizes >0.5 arcseconds. In addition to the images, high quality astrometry is an equally important product of this work allowing reliable source identification in a crowded field. Radio sources associated with compact galaxies have been used to align both the HST WFPC2 frames and a CFHT optical field to the ICRF. The HST optical field has been aligned to better than 50 mas in the Deep Field itself, and to ∼150 mas in the outer parts of the Flanking Fields. The proportion of starburst systems is found to increase with decreasing source strength. At fluxes below 100µJy in excess of 70% of the µJy sources are found to be starburst type systems associated with major disc galaxies in the redshift range 0.3 - 1.3. Some 40% of the brighter sources are found to be intermediate luminosity AGN systems identified with galxies in a similar redshift range. Around 85% of the sources are identified with galaxies brighter than I=25mag. The remaining 15% are associated with optically faint systems close to or beyond the HDF limit; many of these may be dust-shrouded starburst galaxies at high redshift (z>3). Approaching half the sources in the 10 arcminute field are detected in X-rays by the Chandra Satellite. The X-ray detection rate appears to be uncorrelated with the radio source classification.
- ID:
- ivo://CDS.VizieR/J/MNRAS/235/1313
- Title:
- Metrewave Extragalactic Variability
- Short Name:
- J/MNRAS/235/1313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a detailed statistical study of the intensity variations in 412 extragalactic radio sources randomly selected from the ~2000 sources which have been observed with the Culgoora circular array at 80 and 160 MHz during the interval 1970-84. Our results are: (i) About 47 per cent of the sample displays significant variability on time scales of months or years. (ii) A similar degree of variability is shown by QSOs, radio galaxies and sources in blank optical fields. (iii) Sources with flatter radio spectra are more variable. (iv) There is a weak increase in variability for the lower-galactic-latitude sources. (v) There is a correlation between month-to-month variability and year-to year variability in the same sources. (vi) The degree of variability at 80MHz is related to that at 160MHz. (vii) Most of the sources in both the variable and non-variable categories have a component with angular diameter <1arcsec. Our results are partly consistent with an origin in refractive scintillation by large-scale electron density turbulence in the intervening medium. There are, however, serious difficulties in explaining, from the existing theory of slow galactic scintillation, the short time-scale of the scintillation. Our results are probably more in accord with the focusing and occulting effects of compact interstellar ionized structures recently identified at microwave frequencies.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A108
- Title:
- MG B2016+112 radio images
- Short Name:
- J/A+A/630/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6mas in the lensed images by comparing two very long baseline interferometric (VLBI) radio observations at 1.7GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of as. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components, separated by 175 pc, with proper motion of the order of tens {mu}as/yr for the two components at highest magnification ({mu}~350) and of the order of a few mas/yr for the two components at lower magnification ({mu}~2). We propose single Active Galactic Nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (~10^-5^) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.
