- ID:
- ivo://CDS.VizieR/J/A+A/648/A4
- Title:
- LoTSS Deep Fields DR1 photometric redshifts
- Short Name:
- J/A+A/648/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) is a sensitive, high-resolution 120-168MHz survey split across multiple tiers over the northern sky. The first LoTSS Deep Fields data release consists of deep radio continuum imaging at 150 MHz of the Bootes, European Large Area Infrared Space Observatory Survey-North 1 (ELAIS-N1), and Lockman Hole fields, down to rms sensitivities of ~32, 20, and 22 muJy/beam, respectively. In this paper we present consistent photometric redshift (photo-z) estimates for the optical source catalogues in all three fields - totalling over 7 million sources (~5 million after limiting to regions with the best photometric coverage). Our photo-z estimation uses a hybrid methodology that combines template fitting and machine learning and is optimised to produce the best possible performance for the radio continuum selected sources and the wider optical source population. Comparing our results with spectroscopic redshift samples, we find a robust scatter ranging from 1.6 to 2% for galaxies and 6.4 to 7% for identified optical, infrared, or X-ray selected active galactic nuclei (AGN). Our estimated outlier fractions (|z_phot-z_spec|/(1+z_spec)>0.15) for the corresponding subsets range from 1.5 to 1.8% and 18 to 22%, respectively. Replicating trends seen in analyses of previous wide-area radio surveys, we find no strong trend in photo-$z$ quality as a function of radio luminosity for a fixed redshift. We exploit the broad wavelength coverage available within each field to produce galaxy stellar mass estimates for all optical sources at z<1.5. Stellar mass functions derived for each field are used to validate our mass estimates, with the resulting estimates in good agreement between each field and with published results from the literature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/635/A5
- Title:
- LoTSS giant radio galaxies. I.
- Short Name:
- J/A+A/635/A5
- Date:
- 02 Mar 2022 11:49:28
- Publisher:
- CDS
- Description:
- Giant radio galaxies (GRGs) are a subclass of radio galaxies, which have grown to megaparsec scales. GRGs are much rarer than normal-sized radio galaxies (<0.7Mpc) and the reason for their gigantic sizes is still debated. Here, we report on the biggest sample of GRGs identified to date. These objects were found in the LOFAR Two-metre Sky Survey (LoTSS) first data release images, which cover a 424 deg^2^ region. Of the 239 GRGs found, 225 are new discoveries. The GRGs in our sample have sizes ranging from 0.7Mpc to 3.5Mpc and have redshifts (z) between 0.1 and 2.3. Seven GRGs have sizes above 2Mpc and one has a size of ~3.5Mpc. The sample contains 40 GRGs hosted by spectroscopically confirmed quasars. Here, we present the search techniques employed and the resulting catalogue of the newly discovered large sample of GRGs along with their radio properties. In this paper, we also show for the first time that the spectral index of GRGs is similar to that of normal-sized radio galaxies, indicating that most of the GRG population is not dead or is not similar to a remnant-type radio galaxy. We find that 20 out of 239 GRGs in our sample are located at the centres of clusters and we present our analysis on their cluster environment and radio morphology.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/5049
- Title:
- Low-frequency study of 3C 31 with LOFAR
- Short Name:
- J/MNRAS/474/5049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178MHz), Very Large Array (VLA; 290-420MHz), Westerbork Synthesis Radio Telescope (WSRT; 609MHz) and Giant Metre Radio Telescope (GMRT; 615MHz) observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/17
- Title:
- Luminosity functions for 1.3<z<3.2 galaxies
- Short Name:
- J/ApJ/786/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 4.5 {mu}m luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3<z<3.2. The clusters were identified as Spitzer/Infrared Array Camera (IRAC) color-selected overdensities in the Clusters Around Radio-Loud AGN project, which imaged 420 powerful radio-loud active galactic nuclei (RLAGNs) at z>1.3. The luminosity functions are derived for different redshift and richness bins, and the IRAC imaging reaches depths of m*+2, allowing us to measure the faint end slopes of the luminosity functions. We find that {alpha}=-1 describes the luminosity function very well in all redshift bins and does not evolve significantly. This provides evidence that the rate at which the low mass galaxy population grows through star formation gets quenched and is replenished by in-falling field galaxies does not have a major net effect on the shape of the luminosity function. Our measurements for m* are consistent with passive evolution models and high formation redshifts (z_f_~3). We find a slight trend toward fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. Modeling shows that a contribution of a star-forming population of up to 40% cannot be ruled out. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z~1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of RLAGNs - which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift - and they may therefore be older and more evolved systems than the general protocluster population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/479/3509
- Title:
- LVHIS. far-infrared radio correlation
- Short Name:
- J/MNRAS/479/3509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we measure the far-infrared (FIR) and radio flux densities of a sample of 82 local gas-rich galaxies, including 70 "dwarf" galaxies (M_*_<10^9^M_{sun}_), from the Local Volume HI Survey (LVHIS), which is close to volume limited. It is found that LVHIS galaxies hold a tight linear FIR-radio correlation (FRC) over four orders of magnitude. However, for detected galaxies only, a trend of larger FIR-to-radio ratio with decreasing flux density is observed. We estimate the star formation rate by combining UV and mid-IR data using empirical calibration. It is confirmed that both FIR and radio emission are strongly connected with star formation but with significant non-linearity. Dwarf galaxies are found radiation deficient in both bands, when normalized by star formation rate. It urges a "conspiracy" to keep the FIR-to-radio ratio generally constant. By using partial correlation coefficient in Pearson definition, we identify the key galaxy properties associated with the FIR and radio deficiency. Some major factors, such as stellar mass surface density, will cancel out when taking the ratio between FIR and radio fluxes. The remaining factors, such as HI-to-stellar mass ratio and galaxy size, are expected to cancel each other due to the distribution of galaxies in the parameter space. Such cancellation is probably responsible for the "conspiracy" to keep the FRC alive.
- ID:
- ivo://CDS.VizieR/J/A+A/431/793
- Title:
- Ly-alpha emitters around MRC 0316-257
- Short Name:
- J/A+A/431/793
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the radio galaxy MRC 0316-257 at z=3.13 and the surrounding field resulted in the discovery of 77 candidate Ly{alpha} emitters with a rest-frame equivalent width of >15{AA}. 31 of 40 candidate emitters observed spectroscopically have redshifts similar to that of the radio galaxy. The properties of the Ly{alpha} emission line of the 31 confirmed emitters and the radio galaxy are presented in the file table2.dat (Table 2 in the paper). The magnitudes and continuum slopes of these z~3.1 galaxies are printed in the file table4.dat (Table 4 in the paper). The Ly{alpha} galaxies are faint, blue and small, consistent with the emitters being young starforming galaxies which are still nearly dust free.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/L66
- Title:
- Ly{alpha} emitters near B3 J2330+3927
- Short Name:
- J/MNRAS/400/L66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of a candidate of giant radio-quiet Ly{alpha} blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Ly{alpha} halo B3 J2330+3927 at redshift z=3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Ly{alpha} emitters (LAEs) and absorbers (LAAs) at redshift z=3.09+/-0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31x24arcmin^2^ (58x44 comoving Mpc).
- ID:
- ivo://CDS.VizieR/J/A+A/596/A86
- Title:
- Lynx-Cancer void sample galaxies HI data
- Short Name:
- J/A+A/596/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Void population consists mainly of late-type and low surface brightness (LSB) dwarf galaxies, whose atomic hydrogen is the main component of their baryonic matter. Therefore observations of void galaxy HI are mandatory to understand both their evolution and dynamics. Our aim was to obtain integrated HI parameters for a fainter part of the nearby Lynx-Cancer void galaxy sample (total of 45 objects) with the Nancay Radio Telescope (NRT) and to conduct the comparative analysis of the whole 103 void galaxies with known HI data with a sample of similar galaxies residing in denser environments of the Local Volume. For HI observations we used the NRT with its sensitive antenna/receiver system FORT and standard processing. The comparison of the void and "control" samples on the parameter M(HI)/L_B_ is conducted with the non-parametric method "The 2x2 Contingency Table test". We obtained new HI data for about 40% of the Lynx-Cancer galaxy sample. Along with data from the literature, we use for further analysis data for 103 void objects. The proxy of the evolutional parameter M(HI)/L_B_ of the void sample is compared with that of 82 galaxies of morphological types 8-10 residing in the Local Volume groups and aggregates. At the confidence level of P=0.988, we conclude that for the same luminosity, these void galaxies are systematically gas-richer, in average by ~39%. This result is consistent with the authors' earlier conclusion on the smaller gas metallicities and evidences for the slower low-mass galaxy evolution in voids.
- ID:
- ivo://CDS.VizieR/J/ApJS/230/20
- Title:
- Machine learning technique to classify CoNFIG gal.
- Short Name:
- J/ApJS/230/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff-Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)-Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ~200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a "fusion classifier," which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A23
- Title:
- M82-A radio continuum and polarisation study I.
- Short Name:
- J/A+A/555/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the cosmic ray propagation and determine the magnetic field strength and dominant loss processes in the nearby prototypical starbursting galaxy M82, a multi-frequency analysis at four radio wavelengths is presented. Archival data from the Westerbork Synthesis Radio Telescope (WSRT) was reduced and a new calibration technique introduced to reach the high dynamic ranges needed for the complex source morphology. These data were combined with archival Very Large Array (VLA) data, yielding total power maps at {lambda}3cm, {lambda}6cm, {lambda}22cm, and {lambda}92cm. The data show a confinement of the emission at wavelengths of {lambda}3/{lambda}6cm to the core region and a largely extended halo reaching up to 4kpc away from the galaxy midplane at wavelengths of {lambda}22/{lambda}92cm up to a sensitivity limit of 90uJy and 1.8mJy respectively indicating different physical processes in the core and halo regions. The results are used to calculate the magnetic field strength to 98uG in the core region and to 24uG in the halo regions. From the observation of ionisation losses, the filling factor of the ionised medium could be estimated to 2%. This leads to a revised view of the magnetic field distribution in the core region and the propagation processes from the core into the halo regions.
