- ID:
- ivo://CDS.VizieR/J/AJ/146/10
- Title:
- Spectroscopy of 120 emission-line ICRF2 candidates
- Short Name:
- J/AJ/146/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58m European Southern Observatory New Technology Telescope, the two 8.2m Gemini telescopes, the 2.5m Nordic Optical Telescope (NOT), and the 6.0m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy & Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z>4.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/570/A55
- Title:
- Spiderweb galaxy 870um and 1.4GHz images
- Short Name:
- J/A+A/570/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present APEX LABOCA 870{mu}m observations of the field around the high-redshift radio galaxy MRC1138-262 at z=2.16. We detect 16 submillimeter galaxies (SMGs) in this ~140-arcmin^2^ bolometer map with flux densities in the range 3-11mJy. The raw number counts indicate a density of SMGs that is up to four times that of blank field surveys. Based on an exquisite multiwavelength database, including VLA 1.4 GHz radio and infrared observations, we investigate whether these sources are members of the protocluster structure at z=~2.2. Using Herschel PACS and SPIRE and Spitzer MIPS photometry, we derive reliable far-infrared (FIR) photometric redshifts for all sources. Follow-up VLT ISAAC and SINFONI NIR spectra confirm that four of these SMGs have redshifts of z=~2.2. We also present evidence that another SMG in this field, detected earlier at 850{mu}m, has a counterpart that exhibits H{alpha} and CO(1-0) emission at z=2.15. Including the radio galaxy and two SMGs with FIR photometric redshifts at z=2.2, we conclude that at least eight submm sources are part of the protocluster at z=2.16 associated with the radio galaxy MRC1138-262. We measure a star formation rate density SFRD~1500M_{sun}_/yr/Mpc^3^, four magnitudes higher than the global SFRD of blank fields at this redshift. Strikingly, these eight sources are concentrated within a region of 2Mpc (the typical size of clusters in the local universe) and are distributed within the filaments traced by the HAEs at z=~2.2. This concentration of massive, dusty starbursts is not centered on the submillimeter-bright radio galaxy which could support the infalling of these sources into the cluster center. Approximately half (6/11) of the SMGs that are covered by the H{alpha} imaging data are associated with HAEs, demonstrating the potential of tracing SMG counterparts with this population. To summarize, our results demonstrate that submillimeter observations may enable us to study (proto)clusters of massive, dusty starbursts.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/79
- Title:
- Spitzer observations of radio-loud AGNs (CARLA)
- Short Name:
- J/ApJ/769/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2<z<3.2. These data, obtained for 387 fields, reach 3.6 and 4.5{mu}m depths of [3.6]_AB_=22.6 and [4.5]_AB_=22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6]-[4.5]>-0.1 (AB), which efficiently selects high-redshift (z>1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a>=2{sigma} level; 10% are overdense at a>=5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.
- ID:
- ivo://CDS.VizieR/J/A+A/508/117
- Title:
- Spitzer selected starbursts at z~2
- Short Name:
- J/A+A/508/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wide-field Spitzer surveys allow identification of thousands of potentially high-z submillimeter galaxies (SMGs) through their bright 24um emission and their mid-IR colors. We want to determine the average properties of such z~2 Spitzer-selected SMGs by combining millimeter, radio, and infrared photometry for a representative IR-flux (lambda_rest_~8um) limited sample of SMG candidates. A complete sample of 33 sources believed to be starbursts (5.8um-peakers) was selected in the (0.5deg^2^) J1046+56 field with selection criteria F_24um>400uJy, the presence of a redshifted stellar emission peak at 5.8um, and r'_Vega_>23. The field, part of the SWIRE Lockman Hole field, benefits from very deep VLA/GMRT 20cm, 50cm, and 90cm radio data (all 33 sources are detected at 50cm), and deep 160um and 70um Spitzer data. The 33 sources, with photometric redshifts ~1.5-2.5, were observed at 1.2mm with IRAM-30m/MAMBO to an rms ~0.7-0.8mJy in most cases. Their millimeter, radio, 7-band Spitzer, and near-IR properties were jointly analyzed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/500/3821
- Title:
- Square Kilometre Array Science Data Challenge 1
- Short Name:
- J/MNRAS/500/3821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As the largest radio telescope in the world, the Square Kilometre Array (SKA) will lead the next generation of radio astronomy. The feats of engineering required to construct the telescope array will be matched only by the techniques developed to exploit the rich scientific value of the data. To drive forward the development of efficient and accurate analysis methods, we are designing a series of data challenges that will provide the scientific community with high-quality datasets for testing and evaluating new techniques. In this paper we present a description and results from the first such Science Data Challenge (SDC1). Based on SKA MID continuum simulated observations and covering three frequencies (560MHz, 1400MHz and 9200MHz) at three depths (8h, 100h and 1000h), SDC1 asked participants to apply source detection, characterization and classification methods to simulated data. The challenge opened in November 2018, with nine teams submitting results by the deadline of April 2019. In this work we analyse the results for 8 of those teams, showcasing the variety of approaches that can be successfully used to find, characterise and classify sources in a deep, crowded field. The results also demonstrate the importance of building domain knowledge and expertise on this kind of analysis to obtain the best performance. As high-resolution observations begin revealing the true complexity of the sky, one of the outstanding challenges emerging from this analysis is the ability to deal with highly resolved and complex sources as effectively as the unresolved source population.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/914
- Title:
- Star formation in HI-selected galaxies
- Short Name:
- J/ApJ/613/914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 69 galaxies with radial velocities of less than 2500km/s was selected from the HI Parkes All-Sky Survey (HIPASS, Cat. <VIII/73>) and imaged in broadband B and R and narrowband H{alpha}, to deduce details about star formation in nearby disk galaxies while avoiding surface brightness selection effects.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A114
- Title:
- Star-forming galaxies over 0.35<z<2.25
- Short Name:
- J/A+A/625/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To better constrain the physical mechanisms driving star formation, we present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range 0.35<z<2.25. We use the VLA COSMOS 3GHz map (noise rms=2.3Jy/beam, {theta}_beam_=0.75arcsec) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main-sequence (MS) of SFGs. We constrain the overall extent of star formation activity in galaxies by applying a 2D-Gaussian model to their radio continuum emission. Extensive Monte Carlo simulations are used to validate the robustness of our measurements and characterize the selection function. We find no clear dependence between the radio size and stellar mass, M*, of SFGs with 10.5<log(M*/M_{sun}_)<11.5. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of Reff=1.5+/-0.2(1.0+/-0.2)kpc remains nearly constant with cosmic time; a parametrization of the form Reff{prop.to}(1+z)^alpha^ yields a shallow slope of only alpha=-0.26+/-0.08(0.12+/-0.14) for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than that inferred from radio continuum emission by a factor ~2(1.3) at z=0.5(2), indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density ({SIGMA}_SFR_) scales with the distance to the MS, except for a fraction of MS galaxies (~10%) that harbor starburst-like {SIGMA}_SFR_. These "hidden" starbursts might have experienced a compaction phase due to disk instability and/or merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to use {SIGMA}_SFR_ and distance to the MS in conjunction to better identify the galaxy population undergoing a starbursting phase.
- ID:
- ivo://CDS.VizieR/J/AZh/87/739
- Title:
- Steep and ultra-steep spectra RC sources
- Short Name:
- J/AZh/87/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopy of 71 objects with steep and ultra-steep spectra (alpha<-0.9, S{prop.to}nu^alpha^) from the "Big Trio" (RATAN-600-VLA-BTA) project, performed with the "Scorpio" spectrograph on the 6-m telescope of the Special Astrophysical Observatory (Russian Academy of Sciences). Redshifts were determined for these objects. We also present several other parameters of the sources, such as their R magnitudes, maximum radio sizes in seconds of arc, flux densities at 500, 1425, and 3940MHz, radio luminosities at 500 and 3940MHz, and morphology. Of the total number of radio galaxies studied, four have redshifts 1<=z<2, three have 2<=z<3, one has 3<=z<4, and one has z=4.51. Thirteen sources have redshifts 0.7<z<1 and 15 have 0.2<z<0.7. Of all the quasars studied, five have redshifts 0.7<z<1, seven have 1<=z<2, four have 2<=z<3, and one has z=3.57. We did not detect any spectral lines for 17 objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/37
- Title:
- Stellar specific angular momentum & mass relation
- Short Name:
- J/ApJ/860/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the relation between stellar specific angular momentum j*, stellar mass M*, and bulge-to-total light ratio {beta} for The HI Nearby Galaxy Survey, the Calar Alto Legacy Integral Field Area Survey, and Romanowsky & Fall (2012ApJS..203...17R) data sets, exploring the existence of a fundamental plane between these parameters, as first suggested by Obreschkow & Glazebrook (2014ApJ...784...26O). Our best-fit M*-j* relation yields a slope of {alpha}=1.03+/-0.11 with a trivariate fit including {beta}. When ignoring the effect of {beta}, the exponent {alpha}=0.56+/-0.06 is consistent with {alpha}=2/3 that is predicted for dark matter halos. There is a linear {beta}-j*/M* relation for {beta}<~0.4, exhibiting a general trend of increasing {beta} with decreasing j*/M*. Galaxies with {beta}>~0.4 have higher j* than predicted by the relation. Pseudobulge galaxies have preferentially lower {beta} for a given j*/M* than galaxies that contain classical bulges. Pseudobulge galaxies follow a well- defined track in {beta}-j*/M* space, consistent with Obreschkow & Glazebrook, while galaxies with classical bulges do not. These results are consistent with the hypothesis that while growth in either bulge type is linked to a decrease in j*/M*, the mechanisms that build pseudobulges seem to be less efficient at increasing bulge mass per decrease in specific angular momentum than those that build classical bulges.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1442
- Title:
- 78 Stripe82 galaxies masses
- Short Name:
- J/MNRAS/478/1442
- Date:
- 19 Jan 2022 11:53:49
- Publisher:
- CDS
- Description:
- We present a cross-calibration of CO- and dust-based molecular gas masses at z<=0.2. Our results are based on a survey with the IRAM 30-m telescope collecting CO(1-0) measurements of 78 massive (logM*/M_{sun}_>10) galaxies with known gas-phase metallicities and with IR photometric coverage from Wide-field Infrared Survey Explorer(WISE; 22um) and Herschel Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, 500um). We find a tight relation (~0.17dex scatter) between the gas masses inferred from CO and dust continuum emission, with a minor systematic offset of 0.05dex. The two methods can be brought into agreement by applying a metallicity-dependent adjustment factor (~0.13dex scatter). We illustrate that the observed offset is consistent with a scenario in which dust traces not only molecular gas but also part of the HI reservoir, residing in the H_2_-dominated region of the galaxy. Observations of the CO(2-1) to CO(1-0) line ratio for two-thirds of the sample indicate a narrow range in excitation properties, with a median ratio of luminosities <R_21_>~0.64. Finally, we find dynamical mass constraints from spectral line profile fitting to agree well with the anticipated mass budget enclosed within an effective radius, once all mass components (stars, gas, and dark matter) are accounted for.
