- ID:
- ivo://CDS.VizieR/J/A+A/657/A25
- Title:
- A521 and Cosmic Snake ALMA abd HST images
- Short Name:
- J/A+A/657/A25
- Date:
- 16 Mar 2022 13:03:06
- Publisher:
- CDS
- Description:
- We study the spatially resolved physical properties of the Cosmic Snake arc in MACS J1206.2-0847 and the arc in Abell 0521 (A521). These are two strongly lensed galaxies at redshifts z=1.036 and z=1.044. We used observations of the Hubble Space Telescope (HST) and the Atacama Large Millimeter/submillimeter Array (ALMA). The former gives access to the star formation rate (SFR) and stellar mass (M*), and the latter to the H_2_ molecular gas mass (Mmol). HST and ALMA observations have similar angular resolutions of 0.15"-0.2", which with the help of strong gravitational lensing enable us to reach spatial resolutions down to ~30pc and ~100pc in these two galaxies, respectively. These resolutions are close to the resolution of observations of nearby galaxies. We study the radial profiles of SFR, M*, and Mmol surface densities of these high-redshift galaxies and compare the corresponding exponential scale lengths with those of local galaxies. We find that the scale lengths in the Cosmic Snake are about 0.5kpc-1.5kpc, and they are 3 to 10 times larger in A521. This is a significant difference knowing that the two galaxies have comparable integrated properties. These high-redshift scale lengths are nevertheless comparable to those of local galaxies, which cover a wide distribution. The particularity of our high-redshift radial profiles is the normalisation of the Mmol surface density profiles (Sigma Mmol), which are offset by up to a factor of 20 with respect to the profiles of z=0 counterparts. The SFR surface density profiles are also offset by the same factor as {SIGMA}Mmol, as expected from the Kennicutt-Schmidt law.
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- ID:
- ivo://CDS.VizieR/J/A+A/647/A3
- Title:
- Abell 3391-Abell 3395 ASKAP/EMU image
- Short Name:
- J/A+A/647/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The pre-merging system of galaxy clusters Abell 3391-Abell 3395 located at a mean redshift of 0.053 has been observed at 1GHz in an ASKAP/EMU Early Science observation as well as in X-rays with eROSITA. The projected separation of the X-ray peaks of the two clusters is ~50{deg} or ~3.1Mpc. Here we present an inventory of interesting radio sources in this field around this cluster merger. While the eROSITA observations provide clear indications of a bridge of thermal gas between the clusters, neither ASKAP nor MWA observations show any diffuse radio emission coinciding with the X-ray bridge. We derive an upper limit on the radio emissivity in the bridge region of <J>_1GHz_<1.2x10^-44^W/H/m3. A non-detection of diffuse radio emission in the X-ray bridge between these two clusters has implications for particle-acceleration mechanisms in cosmological large-scale structure. We also report extended or otherwise noteworthy radio sources in the 30deg^2^ field around Abell 3391-Abell 3395. We identified 20 Giant Radio Galaxies, plus 7 candidates, with linear projected sizes greater than 1Mpc. The sky density of field radio galaxies with largest linear sizes of >0.7Mpc is ~1.7deg^2^, three times higher than previously reported. We find no evidence for a cosmological evolution of the population of Giant Radio Galaxies. Moreover, we find seven candidates for cluster radio relics and radio halos.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A152
- Title:
- Abell 1795 GMRT and Chandra maps
- Short Name:
- J/A+A/618/A152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we analyze AGN activity signatures in the rich nearby galaxy cluster Abell 1795 aiming to confirm and characterize the long-term feedback history in the system. We combine radio observations at 610 and 235MHz from the Giant Metrewave Radio Telescope (GMRT) with 3.4Msec X-ray data from the Chandra Observatory. Extracting radial temperature profiles, as well as Xray and radio surface brightness profiles in three directions showing major morphological disturbances, we highlight the signatures of activity in the system. For the first time we observe radio emission corresponding to the NW X-ray depression, which provides evidence in favor of the classification of the depression as a cavity. We identify two other X-ray cavities situated NW and SW of the AGN. While the central radio emission corresponding to the inner cavities shows a flatter spectral index, the radio extensions associated with the farthest X-ray cavities consist of aged plasma. All observed signatures both in radio and X-ray are consistent with several consecutive episodes of AGN activity, which gave rise to the observed morphology NW and SW from the core. In the southern region, we confirm the cooling wake hypothesis for the origin of the long tail. The deep X-ray data also allows us to distinguish significant distortions in the tail's inner parts, which we attribute to the activity of the AGN.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/1519
- Title:
- Abell 1367 HI sources from AGES
- Short Name:
- J/MNRAS/383/1519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 21cm HI line observations of 5x1deg^2^ centred on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. One hundred sources are detected (79 new HI measurements and 50 new redshifts), more than half belonging to the cluster core and its infalling region. Combining the HI data with Sloan Digital Sky Survey (SDSS) optical imaging, we show that our HI selected sample follows scaling relations similar to the ones usually observed in optically selected samples. Interestingly, all galaxies in our sample appear to have nearly the same baryon fraction independently of their size, surface brightness and luminosity. The most striking difference between HI and optically selected samples resides in their large-scale distribution: whereas optical and X-ray observations trace the cluster core very well, in HI there is almost no evidence of the presence of the cluster. Some implications on the determination of the cluster luminosity function and HI distribution for samples selected at different wavelength are also discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A22
- Title:
- Abell 1914 multiwavelength radio images
- Short Name:
- J/A+A/622/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A number of radio observations have revealed the presence of large synchrotron-emitting sources associated with the intra-cluster medium. There is strong observational evidence that the emitting particles have been (re-)accelerated by shocks and turbulence generated during merger events. The particles that are accelerated are thought to have higher initial energies than those in the thermal pool but the origin of such mildly relativistic particles remains uncertain and needs to be further investigated. The galaxy cluster Abell 1914 is a massive galaxy cluster in which X-ray observations show clear evidence of merging activity. We carried out radio observations of this cluster with the LOw Frequency ARay (LOFAR) at 150MHz and the Giant Metrewave Radio Telescope (GMRT) at 610MHz. We also analysed Very Large Array (VLA) 1.4GHz data, archival GMRT 325MHz data, CFHT weak lensing data and Chandra observations. Our analysis shows that the ultra-steep spectrum source (4C38.39; {alpha}<~-2), previously thought to be part of a radio halo, is a distinct source with properties that are consistent with revived fossil plasma sources. Finally, we detect some diffuse emission to the west of the source 4C38.39 that could belong to a radio halo.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A37
- Title:
- Abell 1775 radio images
- Short Name:
- J/A+A/649/A37
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Thermal gas in the center of galaxy clusters can show substantial motions that generate surface brightness and temperature discontinuities known as cold fronts. The motions may be triggered by minor or o-axis mergers that preserve the cool-core of the system. The dynamics of the thermal gas can also generate radio emission from the intra-cluster medium (ICM) and impact the evolution of clusters radio sources. We study the central region of Abell 1775, a system in an ambiguous dynamical state at z=0.072 which is known to host an extended head-tail radio galaxy, with the aim of investigating the connection between thermal and non-thermal components in its center. We made use of a deep (100ks) Chandra observation accompanied by LOFAR 144MHz, GMRT 235MHz and 610MHz, and VLA 1.4GHz radio data. We find a spiral-like pattern in the X-ray surface brightness that is mirrored in the temperature and pseudo-entropy maps. Additionally, we characterize an arc-shaped cold front in the ICM. We interpret these features in the context of a slingshot gas tail scenario. The structure of the head-tail radio galaxy "breaks" at the position of the cold front, showing an extension that is detected only at low frequencies, likely due to its steep and curved spectrum. We speculate that particle re-acceleration is occurring in the outer region of this tail, that in total covers a projected size of 800kpc. We also report the discovery of revived fossil plasma with ultra-steep spectrum radio emission in the cluster core together with a central diffuse radio source that is bounded by the arc-shaped cold front. The results reported in this work demonstrate the interplay between thermal and non-thermal components in the cluster center and the presence of ongoing particle re-acceleration in the ICM on different scales.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A172
- Title:
- Abell 2626 radio source LOFAR image at 144MHz
- Short Name:
- J/A+A/643/A172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new LOFAR data of the galaxy cluster Abell 2626. Weproduced a new, resolved spectral index map of the source with a resolution of 7" and we studied the spatial correlation of radio and X-ray emission to investigate the interplay between thermal and nonthermal plasma. The new LOFAR data changed our view of the Kite because we discovered two steep-spectrum ({alpha}<-1.5) plumes of emission connected to the arcs. On the basis of our results, we propose that the Kite was originally an X-shaped radio galaxy whose fossil radio plasma, after the end of the activity of the central active galactic nucleus, has been compressed as a consequence of motions of the thermal plasma encompassing the galaxy. The interplay between the compression and advection of the fossil plasma, with the restarting of the nuclear activity of the central galaxy,could have enhanced the radio emission of the fossil plasma producing the arcs of the Kite. We also present the first, low-frequency observation of a jellyfish galaxy in the same field, in which we detect extended, low-frequency emission without a counterpart at higher frequencies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/4485
- Title:
- Absolute polarimetry observations of 33 pulsars
- Short Name:
- J/MNRAS/453/4485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Absolute polarimetry observations of 33 pulsars were carried out with the Green Bank Telescope in the 1100-1900 MHz band using the Green Bank Ultimate Pulsar Processing Instrument. This group was selected to help complete a larger sample for which accurate proper-motion measurements were available. A combination of profile analysis using the core/double cone model and polarization-angle fitting methods were applied to estimate the "fiducial" longitude of the magnetic axis for each star and refer the linear polarization angle at that point to infinite frequency. As had been found previously, a number of the pulsars are found to have fiducial polarization directions that fall either along or at right angles to their proper-motion directions, whereas upwards of a third of the stars studied show alignments that are neither parallel nor orthogonal.
- ID:
- ivo://CDS.VizieR/J/ApJS/220/7
- Title:
- Abundance of X-shaped radio sources. I. VLA survey
- Short Name:
- J/ApJS/220/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cheung (2007, J/AJ/133/2097) identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here, we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1". Fifty-one of the 52 were observed at 1.4GHz, 7 were observed at 1.4 and 5GHz, and 1 was observed only at 5GHz. We also present overlays of the Sloan Digital Sky Survey red images for 48 of the sources, and DSS-II overlays for the remainder. Optical counterparts have been identified for most sources, but there remain a few empty fields. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% of sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A78
- Title:
- A case study of the HI content of HCG 16
- Short Name:
- J/A+A/632/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hickson Compact Group (HCG) 16 is a prototypical compact group of galaxies in an intermediate stage of the evolutionary sequence proposed by Verdes-Montenegro et al. (2001A&A...377..812V), where its galaxies are losing gas to the intra-group medium (IGrM). The group hosts galaxies that are HI-normal, HI-poor, centrally active with both AGN and starbursts, as well as a likely new member and a 160kpc long HI tidal feature. Despite being a well-studied group at all wavelengths, no previous study of HCG 16 has focused on its extraordinary HI component. The characteristics of HCG 16 make it an ideal case study for exploring which processes are likely to dominate the late stages of evolution in compact groups, and ultimately determine their end states. In order to build a coherent picture of the evolution of this group we make use of the multi-wavelength data available, but focus particularly on HI as a tracer of interactions and evolutionary phase. We reprocess archival VLA L-band observations of HCG 16 using the multi-scale CLEAN algorithm to accurately recover diffuse features. Tidal features and galaxies are separated in 3 dimensions using the SlicerAstro package. The HI deficiency of the separated galaxies is assessed against the benchmark of recent scaling relations of isolated galaxies. This work has been performed with particular attention to reproducibility and is accompanied by a complete workflow to reproduce all the final data products, figures, and results. Despite the clear disruption of the HI component of HCG 16 we find that it is not globally HI deficient, even though HCG 16a and b have lost the majority of their HI and almost 50% of the group's HI is in the IGrM. The HI content of HCG 16d shows highly disturbed kinematics, with only a marginal velocity gradient that is almost perpendicular to its optical major axis. The ~160kpc long tail extending towards the South-East appears to be part of an even larger structure which spatially and kinematically connects NGC 848 to the North-West corner of the group. This study indicates that in the recent past (1Gyr) galaxies HCG 16a and b likely underwent major interactions that unbound gas without triggering significant star formation. This gas was then swept away by a high speed, close encounter with NGC 848. The starburst events HCG 16c and d, likely initiated by their mutual interaction, have triggered galactic winds which, in the case of HCG 16d, appears to have disrupted its HI reservoir. The tidal features still connected to all these galaxies indicate that more HI will soon be lost to the IGrM, while that which remains in the discs will likely be consumed by star formation episodes triggered by their on-going interaction. This is expected to result in a collection of gas-poor galaxies embedded in a diffuse HI structure, which will gradually (over several Gyr) be evaporated by the UV background, resembling the final stage of the evolutionary model of compact groups.
