- ID:
- ivo://CDS.VizieR/J/ApJS/202/2
- Title:
- VLA 1.4GHz observations of A370 and A2390
- Short Name:
- J/ApJS/202/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 1.4GHz catalogs for the cluster fields A370 and A2390 observed with the Very Large Array. These are two of the deepest radio images of cluster fields ever taken. The A370 image covers an area of 40'x40' with a synthesized beam of ~1.7" and a noise level of ~5.7uJy near the field center. The A2390 image covers an area of 34'x34' with a synthesized beam of ~1.4" and a noise level of ~5.6uJy near the field center. We catalog 200 redshifts for the A370 field. We construct differential number counts for the central regions (radius <16') of both clusters. We find that the faint (S_1.4GHz_<3mJy) counts of A370 are roughly consistent with the highest blank field number counts, while the faint number counts of A2390 are roughly consistent with the lowest blank field number counts. Our analyses indicate that the number counts are primarily from field radio galaxies. We suggest that the disagreement of our number counts can be largely attributed to cosmic variance.
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1562. VLA survey of CDF-S. II.
- ID:
- ivo://CDS.VizieR/J/ApJS/179/95
- Title:
- VLA survey of CDF-S. II.
- Short Name:
- J/ApJS/179/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical and infrared identifications of the 266 radio sources detected at 20cm with the Very Large Array in the Chandra Deep Field-South. Using deep i-band Advanced Camera for Surveys, R-band Wide Field Imager, K-band SOFI NTT, K-band ISAAC VLT and Spitzer imaging data, we are able to find reliable counterparts for 254 (~95%) VLA sources. Twelve radio sources remain unidentified, and three of them are "empty fields". Using literature and our own data we are able to assign redshifts to 186 (~70%) radio sources: 108 are spectroscopic redshifts and 78 are reliable photometric redshifts. Based on the rest-frame colors and morphological distributions of the host galaxies, we find evidences for a change in the submillijansky radio source population: (1) above ~0.08mJy early-type galaxies are dominating and (2) at flux densities below ~0.08mJy, starburst galaxies become dominant.
- ID:
- ivo://CDS.VizieR/J/AJ/151/74
- Title:
- VLA/VLBA obscured radio-loud active galactic nuclei
- Short Name:
- J/AJ/151/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Yan et al. 2012AJ....144..124Y. In this paper, we present both high-resolution radio continuum images for all of these sources and H I 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.5" and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ~three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H I 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral "window" (i.e., the percentage of H I 21 cm absorption-line detections could be as high as ~90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H I detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H I absorption may well be present but is masked by the RFI. Future searches for highly redshifted H I and molecular absorption can easily find more distant CSOs among bright, "blank field" radio sources, but will be severely hampered by an inability to determine accurate spectroscopic redshifts due to their lack of rest-frame UV continuum.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/113
- Title:
- VLBA astrometry combined with Gaia DR1 epoch
- Short Name:
- J/ApJ/861/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The canonical methods for gravitational wave detection are ground- and space- based laser interferometry, pulsar timing, and polarization of the cosmic microwave background. But as has been suggested by numerous investigators, astrometry offers an additional path to gravitational wave detection. Gravitational waves deflect light rays of extragalactic objects, creating apparent proper motions in a quadrupolar (and higher-order modes) pattern. Astrometry of extragalactic radio sources is sensitive to gravitational waves with frequencies between roughly 10^-18^ and 10^-8^Hz (H_0_ and 1/3yr^-1^), overlapping and bridging the pulsar timing and CMB polarization regimes. We present a methodology for astrometric gravitational wave detection in the presence of large intrinsic uncorrelated proper motions (i.e., radio jets). We obtain 95% confidence limits on the stochastic gravitational wave background using 711 radio sources, {Omega}_GW_<0.0064, and using 508 radio sources combined with the first Gaia data release: {Omega}_GW_<0.011. These limits probe gravitational wave frequencies 6x10^-18^Hz<~f<~1x10^-9^Hz. Using a WISE-Gaia catalog of 567721 AGN, we predict a limit expected from Gaia alone of {Omega}_GW_<0.0006, which is significantly higher than was originally forecast. Incidentally, we detect and report on 22 new examples of optical superluminal motion with redshifts 0.13-3.89.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/177
- Title:
- VLBA 5GHz observations of Fermi/LAT AGNs
- Short Name:
- J/ApJ/744/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed contemporaneously by the Very Long Baseline Array (VLBA). In total, 232 sources were observed with the VLBA. Ninety sources that were previously observed as part of the VLBA Imaging and Polarimetry Survey (VIPS) have been included in the sample, as well as 142 sources not found in VIPS. This very large, 5GHz flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong {gamma}-ray emission. In particular, we see that {gamma}-ray emission is related to strong, uniform magnetic fields in the cores of the host AGN. Included in this sample are non-blazar AGNs such as 3C84, M82, and NGC 6251. For the blazars, the total VLBA radio flux density at 5GHz correlates strongly with {gamma}-ray flux. The LAT BL Lac objects tend to be similar to the non-LAT BL Lac objects, but the LAT flat-spectrum radio quasars (FSRQs) are significantly different from the non-LAT FSRQs. Strong core polarization is significantly more common among the LAT sources, and core fractional polarization appears to increase during LAT detection.
- ID:
- ivo://CDS.VizieR/J/A+A/466/63
- Title:
- VLBI observations of BL Lac objects
- Short Name:
- J/A+A/466/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present EVN observations of seven BL Lac objects selected from the RGB sample. To investigate the intrinsic radiation property of BL Lac objects, we estimated the Doppler factor with the VLA or MERLIN core and the total 408MHz luminosity for a sample of 170 BL Lac objects. The intrinsic (comoving) synchrotron peak frequency was then calculated by using the estimated Doppler factor. Assuming a Lorentz factor of 5, the viewing angle of jets was constrained. The high-resolution VLBI images of seven sources all show a core-jet structure. We estimated the proper motions of three sources with the VLBI archive data, and find that the apparent speed increases with the distance of components to the core for all of them.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3609
- Title:
- VLBI observations of southern ICRF sources
- Short Name:
- J/AJ/127/3609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 8.4GHz very long baseline interferometry (VLBI) observations of 69 southern hemisphere extragalactic sources in the International Celestial Reference Frame. These are the first in a series of observations intended to image all such sources at milliarcsecond resolution in order to determine their continued suitability for reference-frame use based on intrinsic structure. We use the resultant images to calculate a core fraction, that is, the ratio of core flux density to total flux density, for all observed sources. The resulting distribution, with a mean value of 0.83, suggests that most sources are relatively compact. However, just over half the observed sources show significant extended emission in the form of multiple compact components. These sources are probably poorly suited for high-accuracy reference-frame use unless intrinsic structure and potential variability can be taken into account. Our observations represent the first large, comprehensive VLBI imaging survey in the southern hemisphere, significantly extending the existing limited VLBI surveys and, along with some well-known objects, containing many sources that have never been imaged at milliarcsecond resolution. The overlap with Very Long Baseline Array images of sources between 0{deg} and -35{deg} declination helps determine the limits to imaging with the southern hemisphere-accessible telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJ/663/164
- Title:
- VLT and ACS observations in RDCS J1252.9-2927
- Short Name:
- J/ApJ/663/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an extensive spectroscopic survey, carried out with VLT FORS, and from an extensive multiwavelength imaging data set from the HST Advanced Camera for Surveys and ground-based facilities, of the cluster of galaxies RDCS J1252.9-2927.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A57
- Title:
- VLT/MUSE MACS J0416.1-2403 redshift catalogue
- Short Name:
- J/A+A/646/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A census of faint and tiny star forming complexes at high redshift is key to improving our understanding of reionizing sources, galaxy growth, and the formation of globular clusters. We present the MUSE Deep Lensed Field (MDLF) program, which is aimed at unveiling the very faint population of high redshift sources that are magnified by strong gravitational lensing and to significantly increase the number of constraints for the lens model. We describe Deep MUSE observations of 17.1 hours of integration on a single pointing over the Hubble Frontier Field galaxy cluster MACS J0416, providing line flux limits down to 2x10^19^erg/s/cm^2^ within 300km/s and continuum detection down to magnitude 26, both at the three sigma level at {lambda}=7000{AA}. For point sources with a magnification ({mu}) greater than 2.5 (7.7), the MLDF depth is equivalent to integrating more than 100 (1000) hours in blank fields, as well as complementing non-lensed studies of very faint high-z sources. The source-plane effective area of the MDLF with {mu}>6.3 is <50% of the image-plane field of view. We confirm spectroscopic redshifts for all 136 multiple images of 48 source galaxies at 0.9<z<6.2. Within those galaxies, we securely identify 182 multiple images of 66 galaxy components that we use to constrain our lens model. This makes MACS J0416 the cluster with the largest number of confirmed constraints for any strong lens model to date. We identify 116 clumps belonging to background high-z galaxies; the majority of them are multiple images and span magnitude, size, and redshift intervals of [-18, -10], [~400-3] parsec and 1<z<6.6, respectively, with the faintest or most magnified ones probing possible single gravitationally bound star clusters. The multiplicity introduced by gravitational lensing allows us, in several cases, to triple the effective integration time up to 51 hours exposure per single family, leading to a detection limit for unresolved emission lines of a few 10^-20^erg/s/cm^2^, after correction for lensing magnification. Ultraviolet high-ionization metal lines (and HeII{lambda}1640) are detected with S/N>10 for individual objects down to de-lensed magnitudes between 28-30. The median stacked spectrum of 33 sources with a median M_UV_=~-17 and <z>=3.2 (1.7<z<3.9) shows high-ionization lines, suggesting that they are common in such faint sources. Deep MUSE observations, in combination with existing HST imaging, allowed us to: (1) confirm redshifts for extremely faint high-z sources; (2) peer into their internal structure to unveil clumps down to 100-200pc scale; (3) in some cases, break down such clumps into star-forming complexes matching the scales of bound star clusters (<20pc effective radius); (4) double the number of constraints for the lens model, reaching an unprecedented set of 182 bona-fide multiple images and confirming up to 213 galaxy cluster members. These results demonstrate the power of JWST and future adaptive optics facilities mounted on the Extremely Large Telescopes (e.g., European-ELT Multi-conjugate Adaptive Optics RelaY, MAORY, coupled with the Multi-AO Imaging CamerA for Deep Observations, MICADO) or Very Large Telescope (e.g., MCAO Assisted Visible Imager and Spectrograph, MAVIS) when combined in studies with gravitational telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/78
- Title:
- VLT/MUSE spectroscopic obs. of MACS J1149.5+2223
- Short Name:
- J/ApJ/822/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Multi Unit Spectroscopic Explorer (MUSE) observations in the core of the Hubble Frontier Fields (HFF) galaxy cluster MACSJ1149.5+2223, where the first magnified and spatially resolved multiple images of supernova (SN) "Refsdal" at redshift 1.489 were detected. Thanks to a Director's Discretionary Time program with the Very Large Telescope and the extraordinary efficiency of MUSE, we measure 117 secure redshifts with just 4.8hr of total integration time on a single 1arcmin^2^ target pointing. We spectroscopically confirm 68 galaxy cluster members, with redshift values ranging from 0.5272 to 0.5660, and 18 multiple images belonging to seven background, lensed sources distributed in redshifts between 1.240 and 3.703. Starting from the combination of our catalog with those obtained from extensive spectroscopic and photometric campaigns using the Hubble Space Telescope (HST), we select a sample of 300 (164 spectroscopic and 136 photometric) cluster members, within approximately 500kpc from the brightest cluster galaxy, and a set of 88 reliable multiple images associated with 10 different background source galaxies and 18 distinct knots in the spiral galaxy hosting SN "Refsdal". We exploit this valuable information to build six detailed strong-lensing models, the best of which reproduces the observed positions of the multiple images with an rms offset of only 0.26". We use these models to quantify the statistical and systematic errors on the predicted values of magnification and time delay of the next emerging image of SN "Refsdal". We find that its peak luminosity should occur between 2016 March and June and should be approximately 20% fainter than the dimmest (S4) of the previously detected images but above the detection limit of the planned HST/WFC3 follow-up. We present our two-dimensional reconstruction of the cluster mass density distribution and of the SN "Refsdal" host galaxy surface brightness distribution. We outline the road map toward even better strong-lensing models with a synergetic MUSE and HST effort.
