- ID:
- ivo://CDS.VizieR/J/A+A/653/A87
- Title:
- TOPGot sample, SEDs and CH3CN analysis
- Short Name:
- J/A+A/653/A87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The TOPGot project targets a sample of 86 high-mass star-forming regions in different evolutionary stages from starless cores to ultra compact HII regions. The aim of the survey is to analyze different molecular species in a statistically significant sample to study the chemical evolution in high-mass star-forming regions, and identify chemical tracers of the different phases. In the first paper we present the sample and analyze the spectral energy distributions (SEDs) of the TOPGot sources to derive physical parameters. We also use the MADCUBA software to analyze the emission of methyl cyanide (CH_3_CN), a well-known tracer of high-mass star formation. The emission of the CH_3_CN(5K-4K) K-transitions has been detected towards 73 sources (85% of the sample). The emission of CH_3_CN has been detected towards all evolutionary stages, with the mean abundances showing a clear increase of an order of magnitude from high-mass starless-cores to later evolutionary stages. We found a conservative abundance upper limit for high-mass starless cores of X_CH_3_CN_<4.0x10^-11^, and a range in abundance of 4.0x10^-11^<X_CH_3_CN_<7.0x10^-11^ for those sources that are likely high-mass starless cores or very early high-mass protostellar objects. In fact, in this range of abundance we have identified five sources previously not classified as being in a very early evolutionary stage. The abundance of CH_3_CN can thus be used to identify high-mass star-forming regions in early phases of star-formation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AN/333/634
- Title:
- Torun methanol source catalogue
- Short Name:
- J/AN/333/634
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the observations of 289 methanol maser sources at 6.7GHz obtained over a two month period with the Torun 32m telescope. The data form a catalogue of all objects north of {delta}=22{deg} brighter than 7.5Jy in the peak emission. The positions of sub-arcsecond accuracy are updated for 76% of the objects. We find that about one third of the sources show changes in the peak fluxes by a factor of two or more on time scales of 8.5-9.5 years.
- ID:
- ivo://CDS.VizieR/J/MNRAS/339/913
- Title:
- Two distant massive clusters of galaxies
- Short Name:
- J/MNRAS/339/913
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the radio, optical, and X-ray properties of two newly discovered, very X-ray luminous, distant clusters of galaxies. Both systems were noted as cluster candidates in a cross-correlation of data from the WENSS (<VIII/162>) radio survey and the ROSAT All-Sky Survey (<IX/10>). Follow-up observations performed by us and the Massive Cluster Survey (MACS) team confirmed both sources as distant galaxy clusters. The first cluster, MACS J0717.5+3745 at a redshift of z=0.5548, contains a very extended, steep-spectrum radio source offset from the cluster core, making it the most distant radio relic known. The second cluster, MACS J1621.3+3810 at z=0.465, is a strong cooling flow with a relatively weak central radio source. We present results from ROSAT High-Resolution Imager (HRI, Cat. <IX/28>) observations of both clusters as well as from optical imaging and VLA radio interferometry observations. Our discoveries demonstrate that distant clusters can be efficiently identified in a relatively shallow X-ray survey, that radio/X-ray selection is efficient, and that both cooling flow and non-cooling flow clusters are selected.
- ID:
- ivo://CDS.VizieR/J/ApJS/242/4
- Title:
- Two new catalogs of blazar candidates
- Short Name:
- J/ApJS/242/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two catalogs of radio-loud candidate blazars whose Wide-Field Infrared Survey Explorer (WISE) mid-infrared colors are selected to be consistent with the colors of confirmed {gamma}-ray-emitting blazars. The first catalog is the improved and expanded release of the WISE Blazar-like Radio-Loud Sources (WIBRaLS) catalog presented by D'Abrusco et al. It includes sources detected in all four WISE filters, spatially cross-matched with radio sources in one of three radio surveys and radio-loud based on their q_22_ spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, flat-spectrum radio quasars, or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6], and [12]) only, whose mid-infrared colors are similar to those of confirmed, {gamma}-ray BL Lacs. Members of KDBLLACS are also required to have a radio counterpart and be radio-loud based on the parameter q_12_, defined similarly to the q_22_ used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We cross-match the two new catalogs with the most recent catalogs of {gamma}-ray sources detected by the Fermi Large Area Telescope. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of {gamma}-ray unassociated sources confirmed that ~90% of these candidates are blazars, we anticipate that these new catalogs will again play an important role in the identification of the {gamma}-ray sky.
1545. Type 2 quasars from SDSS
- ID:
- ivo://CDS.VizieR/J/AJ/136/2373
- Title:
- Type 2 quasars from SDSS
- Short Name:
- J/AJ/136/2373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z<0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature.
- ID:
- ivo://CDS.VizieR/J/A+AS/138/87
- Title:
- UBVRI photometry of EUV stellar sources
- Short Name:
- J/A+AS/138/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of high-precision UBV(RI)_c_ photometric observations and of spectroscopic radial velocity measurements obtained at the European Southern Observatory for a sample of 51 cool stars detected in the EUV by the ROSAT Wide Field Camera (WFC). Using also recent results from HIPPARCOS, we infer spectral types and investigate the single or binary nature of the sample stars. Optical variability, with periods in the 0.4-13 day range, has been detected for the first time in 15 of these stars.
1547. UGSs. V. kernel approach
- ID:
- ivo://CDS.VizieR/J/ApJS/209/10
- Title:
- UGSs. V. kernel approach
- Short Name:
- J/ApJS/209/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearly one-third of the {gamma}-ray sources detected by Fermi are still unidentified, despite significant recent progress in this area. However, all of the {gamma}-ray extragalactic sources associated in the second Fermi-LAT catalog have a radio counterpart. Motivated by this observational evidence, we investigate all the radio sources of the major radio surveys that lie within the positional uncertainty region of the unidentified {gamma}-ray sources (UGSs) at a 95% level of confidence. First, we search for their infrared counterparts in the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) and then we analyze their IR colors in comparison with those of the known {gamma}-ray blazars. We propose a new approach, on the basis of a two-dimensional kernel density estimation technique in the single [3.4]-[4.6]-[12]{mu}m WISE color-color plot, replacing the constraint imposed in our previous investigations on the detection at 22{mu}m of each potential IR counterpart of the UGSs with associated radio emission. The main goal of this analysis is to find distant {gamma}-ray blazar candidates that, being too faint at 22{mu}m, are not detected by WISE and thus are not selected by our purely IR-based methods. We find 55 UGSs that likely correspond to radio sources with blazar-like IR signatures. An additional 11 UGSs that have blazar-like IR colors have been found within the sample of sources found with deep recent Australia Telescope Compact Array observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/341/993
- Title:
- u_j_br photometry and redshifts of QSOs
- Short Name:
- J/MNRAS/341/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of a sample of radio-detected quasars, obtained by matching together objects from the FIRST (<VIII/71>) survey and the 2dF Quasar Redshift Survey (2dF, <VII/223>). The data set consists of 113 sources, spanning a redshift range 0.35<~z<~2.2, with optical magnitudes 18.25<=bj<=20.85 and radio fluxes S_1.4GHz_>=1mJy. These objects exhibit properties such as redshift and colour distribution in full agreement with those derived for the whole quasar population, suggesting that the mechanism(s) controlling the birth and lifetime of quasars are independent of their level of radio emission. The long-debated question of the radio-loud/radio quiet (RL/RQ) dichotomy is then investigated for the combined FIRST-2dF and FIRST-LBQS (Large Bright Quasar Survey) samples, as they present similar selection criteria.
- ID:
- ivo://CDS.VizieR/J/ApJ/778/127
- Title:
- UKIDSS+FIRST+SDSS red QSOs candidates
- Short Name:
- J/ApJ/778/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K<=17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190deg^2^. These candidates reach up to ~1.5mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B-V)>0.1, including 3 at z>2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z>~2) are only moderately reddened, with E(B-V)~0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B-V)>~0.5) at z>2 and a depth of K=17, we would need to survey at least ~2.5 times more area.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A92
- Title:
- Ultracompact extragalactic radio sources at 86GHz
- Short Name:
- J/A+A/622/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very long baseline interferometry (VLBI) observations at 86 GHz (wavelength, {lambda}=3mm) reach a resolution of about 50{mu}as, probing the collimation and acceleration regions of relativistic outflows in active galactic nuclei (AGN). The physical conditions in these regions can be studied by performing 86GHz VLBI surveys of representative samples of compact extragalactic radio sources. To extend the statistical studies of compact extragalactic jets, a large global 86GHz VLBI survey of 162 compact radio sources was conducted in 2010-2011 using the Global Millimeter VLBI Array (GMVA). The survey observations were made in a snapshot mode, with up to five scans per target spread over a range of hour angles in order to optimize the visibility coverage. The survey data attained a typical baseline sensitivity of 0.1Jy and a typical image sensitivity of 5mJy/beam, providing successful detections and images for all of the survey targets. For 138 objects, the survey provides the first ever VLBI images made at 86GHz. Gaussian model fitting of the visibility data was applied to represent the structure of the observed sources and to estimate the flux densities and sizes of distinct emitting regions (components) in their jets. These estimates were used for calculating the brightness temperature (Tb) at the jet base (core) and in one or more moving regions (jet components) downstream from the core. These model-fit-based estimates of Tb were compared to the estimates of brightness temperature limits made directly from the visibility data, demonstrating a good agreement between the two methods. The apparent brightness temperature estimates for the jet cores in our sample range from 2.5x10^9^K to 1.3x10^12^K, with the mean value of 1.8x10^11^K. The apparent brightness temperature estimates for the inner jet components in our sample range from 7.0x10^7^K to 4.0x10^11^K. A simple population model with a single intrinsic value of brightness temperature, T0, is applied to reproduce the observed distribution. It yields T0=(3.77^+0.10^_0.14_)10^11^K for the jet cores, implying that the inverse Compton losses dominate the emission. In the nearest jet components, T0=(1.42^+0.16^_0.19_)10^11^K is found, which is slightly higher than the equipartition limit of 5x10^10^K expected for these jet regions. For objects with sufficient structural detail detected, the adiabatic energy losses are shown to dominate the observed changes of brightness temperature along the jet.
