- ID:
- ivo://CDS.VizieR/J/ApJS/118/201
- Title:
- Galactic Center 6 and 20cm survey
- Short Name:
- J/ApJS/118/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the VLA to survey 10 fields at 20 cm (1658MHz) and 11 fields at 6 cm (5GHz) that are between 7' and 137' from SgrA*. Our objective was to identify extragalactic sources and measure their scattering diameters so as to constrain the GC-scattering region separation. In order to find sources within these fields, we have employed pdfCLEAN, a source detection algorithm in which sources are identified in an image by comparing the intensity histogram of the image to that expected from a noise-only image. We found over 100 sources, with the faintest sources being approximately 3 mJy. The average number of sources per field is approximately 10, though fields close to SgrA* tend to contain fewer sources. A number of Galactic sources are included in our source catalog. The double-lobed source 1LC 359.872+0.178, potentially an X-ray quiet version of 1E 1740.7-2942, a shell-like structure with a central point source, and a possible radio transient, are discussed in the paper.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PASJ/52/631
- Title:
- Galactic plane VERA survey
- Short Name:
- J/PASJ/52/631
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to search for new VLBI sources in the galactic plane that can be used as phase reference sources in differential VLBI, we conducted 22GHz observations of radio sources in the galactic plane using the Japanese VLBI Network (J-Net). We have observed 267 VLBI source candidates selected from existing radio surveys and have detected 93 sources at a signal-to-noise ratio larger than 5. While 42 of the 93 detected sources had already been detected with VLBI at relatively lower frequency (typically 2 to 8GHz), the remaining 51 are found to be new VLBI sources detected for the first time. These are located within |b|<=5{deg}, and have a large number of galactic maser sources around them. Thus, they are potential candidates for phase reference sources for VLBI Exploration of Radio Astrometry (VERA), which is the first VLBI array dedicated to phase-referencing VLBI astrometry aimed at measuring the parallax and proper motion of maser sources in the whole Galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/96/1655
- Title:
- Galactic plane VLA survey
- Short Name:
- J/AJ/96/1655
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a continuum VLA snapshot survey of the galactic plane in the longitude range 0{deg}<=l<=90{deg} at 1.5GHz. Observations were taken every 0.5{deg} in longitude at b=0{deg}. Most fields are complete to about 30mJy peak flux density. The positions, peak, and total flux density of 471 compact sources (<30") have been measured. A complete sample of 329 sources is defined. An excess of sources above that expected from extragalactic source counts is seen for l<40{deg} at all flux-density intervals. We find 86 compact sources that are within 2.4arcmin of a source in the recent radio recombination-line survey of Lockman (1989ApJS...71..469L) Source counts excluding these 86 sources agree with extragalactic source counts for all flux-density and longitude intervals. there may only be a small number of galactic objects present in this survey that remain unidentified as such.
- ID:
- ivo://CDS.VizieR/J/AJ/130/156
- Title:
- Galactic radio compact HII regions at 1.4GHz
- Short Name:
- J/AJ/130/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a new Very Large Array Galactic plane catalog at 1.4GHz (Cat. <J/AJ/130/586>) covering the first and second Galactic quadrants (340{deg}<=l<=120{deg}, |b|<=0.8{deg} with |b|<=1.8{deg} for 350{deg}<=l<=40{deg} and |b|<=2.5{deg} for 100{deg}<=l<=105{deg}) in conjunction with the MSX6C (Cat. <V/114>) Galactic plane mid-infrared catalog to supplement and better understand our 5GHz catalog (Cat. <J/ApJS/91/347>).
295. Galaxies near S1189
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/2578
- Title:
- Galaxies near S1189
- Short Name:
- J/MNRAS/406/2578
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radio images of a sample of six wide-angle tail (WAT) radio sources, identified in the Australia Telescope Large Area Survey 1.4-GHz radio survey, and new spectroscopic redshifts for four of these sources. These WATs are in the redshift range of 0.1469-0.3762, and we find evidence of galaxy overdensities in the vicinity of four of the WATs from either spectroscopic or photometric redshifts. We also present follow-up spectroscopic observations of the area surrounding the largest WAT, S1189, which is at a redshift of ~0.22. The spectroscopic observations, taken using the AAOmega spectrograph on the Anglo-Australian Telescope, show an overdensity of galaxies at this redshift. The galaxies are spread over an unusually large area of ~12Mpc with a velocity spread of ~4500km/s. This large-scale structure includes a highly asymmetric Fanaroff-Riley type I radio galaxy and also appears to host a radio relic. It may represent an unrelaxed system with different sub-structures interacting or merging with one another. We discuss the implications of these observations for future large-scale radio surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/141/88
- Title:
- Galaxy cluster environments of radio sources
- Short Name:
- J/AJ/141/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Sloan Digital Sky Survey (SDSS) and the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) catalogs, we examined the optical environments around double-lobed radio sources. Previous studies have shown that multi-component radio sources exhibiting some degree of bending between components are likely to be found in galaxy clusters. Often this radio emission is associated with a cD-type galaxy at the center of a cluster. We cross-correlated the SDSS and FIRST catalogs and measured the richness of the cluster environments surrounding both bent and straight multi-component radio sources. This led to the discovery and classification of a large number of galaxy clusters out to a redshift of z~0.5.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A94
- Title:
- 6 galaxy clusters ATCA 2.1GHz images
- Short Name:
- J/A+A/611/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A fraction of galaxy clusters host diffuse radio sources whose origins are investigated through multi-wavelength studies of cluster samples. We investigate the presence of diffuse radio emission in a sample of seven galaxy clusters in the largely unexplored intermediate redshift range (0.3<z<0.44). In search of diffuse emission, deep radio imaging of the clusters are presented from wide band (1.1-3.1GHz), full resolution (~5-arcsec) observations with the Australia Telescope Compact Array (ATCA). The visibilities were also imaged at lower resolution after point source modelling and subtraction and after a taper was applied to achieve better sensitivity to low surface brightness diffuse radio emission. In case of non-detection of diffuse sources, we set upper limits for the radio power of injected diffuse radio sources in the field of our observations. Furthermore, we discuss the dynamical state of the observed clusters based on an X-ray morphological analysis with XMM-Newton. We detect a giant radio halo in PSZ2 G284.97-23.69 (z=0.39) and a possible diffuse source in the nearly relaxed cluster PSZ2 G262.73-40.92 (z=0.421). Our sample contains three highly disturbed massive clusters without clear traces of diffuse emission at the observed frequencies. We were able to inject modelled radio halos with low values of total flux density to set upper detection limits; however, with our high-frequency observations we cannot exclude the presence of RH in these systems because of the sensitivity of our observations in combination with the high z of the observed clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/77
- Title:
- Galaxy clusters: radio halos, relics and parameters
- Short Name:
- J/ApJ/813/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics, and mini-halos for a sample of galaxy clusters from the literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio powers of relics, halos, and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, while the correlations concerning giant radio halos are in general the strongest. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitatively characterize the shock waves and turbulence in the intracluster medium responsible for re-accelerating particles to generate the observed diffuse radio emission. The power of radio halos and relics is correlated with cluster mass proxies and dynamical parameters in the form of a fundamental plane.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/22
- Title:
- GALFA-HI search for local dwarf galaxies
- Short Name:
- J/ApJ/879/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, ultrafaint dwarf (UFD) galaxies have been found through systematic searches of large optical surveys. However, the existence of Leo T, a nearby gas-rich dwarf, suggests that there could be other nearby UFDs that are optically obscured but have gas detectable at nonoptical wavelengths. With this in mind, we perform a search of the full Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey, a radio survey that covers one-third of the sky at velocities -650<V_LSR_<+650km/s, for neutral hydrogen sources. We are able to probe regions of the sky at lower Galactic latitudes and smaller |V_LSR_| compared to previous explorations. We use the Source Finding Application on GALFA-HI and select all sources with similar properties to Leo T and other local dwarf galaxies. We find 690 dwarf galaxy candidates, one of which is particularly promising and likely a new galaxy near the Galactic plane (b=-8{deg}) that is comparable in velocity width and HI-flux to other recently discovered local volume galaxies. We find we are sensitive to Leo T-like objects out to 1Mpc at velocities clear from background HI emission. We check each candidate's corresponding optical fields from Pan-STARRS and fit stars drawn from isochrones, but find no evidence of stellar populations. We thus find no other Leo T-like dwarfs within 500 kpc of the Milky Way in the one-third of the sky covered by the GALFA-HI footprint, and discuss our nondetection in a cosmological context.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A89
- Title:
- G328.2551-0.5321 ALMA images
- Short Name:
- J/A+A/617/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The conditions leading to the formation of the most massive O-type stars, are still an enigma in modern astrophysics. To assess the physical conditions of high-mass protostars in their main accretion phase, here we present a case study of a young massive clump selected from the ATLASGAL survey, G328.2551-0.5321. The source exhibits a bolometric luminosity of 1.3x10^4^L_{sun}_, which allows us to estimate its current protostellar mass to be between ~11 and 16 M_{sun}_. We show high angular-resolution observations with ALMA reaching a physical scale of ~400au. To reveal the structure of this high-mass protostellar envelope in detail at a ~0.17" resolution, we use the thermal dust continuum emission and spectroscopic information, amongst others from the CO (J=3-2) line, which is sensitive to the high velocity molecular outflow, the SiO (J=8-7), and SO_2_ (J=8_2,6_-7_1,7_) lines tracing shocks along the outflow, as well as several CH_3_OH and HC_3_N lines that probe the gas of the inner envelope in the closest vicinity of the protostar. The dust continuum emission reveals a single high-mass protostellar envelope, down to our resolution limit. We find evidence for a compact, marginally resolved continuum source, which is surrounded by azimuthal elongations that could be consistent with a spiral pattern. We also report on the detection of a rotational line of CH_3_OH within its vt=1 torsionally excited state. This shows two bright peaks of emission spatially offset from the dust continuum peak, and exhibiting a distinct velocity component +/-4.5km/s offset compared to the source Vlsr. Rotational diagram analysis and models based on local thermodynamic equilibrium (LTE) assumption require high CH3OH column densities reaching N(CH_3_OH)=1.2-2x10^19^cm^-2^, and kinetic temperatures of the order of 160-200K at the position of these peaks. A comparison of their morphology and kinematics with those of the outflow component of the CO line, and the SO2 line suggests that the high excitation CH3OH spots are associated with the innermost regions of the envelope. While the HC_3_N v7=0 (J=37-36) line is also detected in the outflow, the HC_3_N v7=1e (J=38-37) rotational transition within the molecule's vibrationally excited state shows a compact morphology. We find that the velocity shifts at the position of the observed high excitation CH3OH spots correspond well to the expected Keplerian velocity around a central object with 15M_{sun}_ consistent with the mass estimate based on the source's bolometric luminosity. We propose a picture where the CH_3_OH emission peaks trace the accretion shocks around the centrifugal barrier, pinpointing the interaction region between the collapsing envelope and an accretion disk. The physical properties of the accretion disk inferred from these observations suggest a specific angular momentum several times larger than typically observed towards low-mass protostars. This is consistent with a scenario of global collapse setting on at larger scales that could carry a more significant amount of kinetic energy compared to the core collapse models of low-mass star formation. Furthermore, our results suggest that vibrationally exited HC_3_N emission could be a new tracer for compact accretion disks around high-mass protostars.
