- ID:
- ivo://CDS.VizieR/J/A+A/621/A139
- Title:
- VLA-COSMOS 3GHz sources average radio SED
- Short Name:
- J/A+A/621/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct the average radio spectral energy distribution (SED) of highly star-forming galaxies (HSFGs) up to z~4. Infrared and radio luminosities are bound by a tight correlation that is defined by the so-called q parameter. This infrared-radio correlation provides the basis for the use of radio luminosity as a star-formation tracer. Recent stacking and survival analysis studies find q to be decreasing with increasing redshift. It was pointed out that a possible cause of the redshift trend could be the computation of rest-frame radio luminosity via a single power-law assumption of the star-forming galaxies' (SFGs) SED. To test this, we constrained the shape of the radio SED of a sample of HSFGs. To achieve a broad rest-frame frequency range, we combined previously published Very Large Array observations of the COSMOS field at 1.4GHz and 3GHz with unpublished Giant Meterwave Radio Telescope (GMRT) observations at 325MHz and 610MHz by employing survival analysis to account for non-detections in the GMRT maps. We selected a sample of HSFGs in a broad redshift range (z{in}[0.3,4], SFR>=100M_{sun}_/yr) and constructed the average radio SED. By fitting a broken power-law, we find that the spectral index changes from {sigma}_1_=0.42+/-0.06 below a rest-frame frequency of 4.3GHz to {sigma}_2_=0.94+/-0.06 above 4.3GHz. Our results are in line with previous low-redshift studies of HSFGs (SFR>10M_{sun}_/yr) that show the SED of HSFGs to differ from the SED found for normal SFGs (SFR<10M_{sun}}/yr). The difference is mainly in a steeper spectrum around 10GHz, which could indicate a smaller fraction of thermal free-free emission. Finally, we also discuss the impact of applying this broken power-law SED in place of a simple power-law in K-corrections of HSFGs and a typical radio SED for normal SFGs drawn from the literature. We find that the shape of the radio SED is unlikely to be the root cause of the q-z trend in SFGs.
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Search Results
- ID:
- ivo://nasa.heasarc/vlacosmos
- Title:
- VLA-COSMOS Large Project 1.4-GHz Source Catalog
- Short Name:
- VLACOSMOS
- Date:
- 21 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The international COSMOS (Cosmic Evolution) survey (Scoville et al. 2007, ApJS, 172, 1) is a panchromatic imaging and spectroscopic survey of a 1.4 degree by 1.4 degree field designed to probe galaxy and SMBH (supermassive black hole) evolution as a function of cosmic environment. One major aspect of the COSMOS survey is the Hubble Space Telescope (HST) Treasury Project (Scoville et al. 2007, ApJS, 172, 38), entailing the largest ever allocation of HST telescope time. The equatorial location of the COSMOS field offers the critical advantage of allowing major observatories from both hemispheres to join forces in this endeavor. State-of-the-art imaging data at all wavelengths (X-ray to centimeter, plus large optical spectroscopic campaigns using the VLT VIMOS and the Magellan IMACS instruments (Lilly et al. 2007; Impey et al. 2007; Trump et al. 2007) have been or are currently being obtained for the COSMOS field. These make the COSMOS field an excellent resource for observational cosmology and galaxy evolution in the important redshift range z ~ 0.5 - 3, a time span covering ~ 75% of the lifetime of the universe. The VLA-COSMOS Large Project produced a catalog of 3643 radio sources found in the 2 square degrees COSMOS field at 1.4 GHz with a signal-to-noise threshold S/N >= 4.5. The observations in the VLA A and C configurations resulted in a resolution of 1.5" by 1.4" and a mean rms noise of ~ 10.5 µJy (µJy) beam<sup>-1</sup> in the central 1 deg<sup>2</sup>, and of 15 uJy in the 2 deg<sup>2</sup> field. Eighty radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested, and the uncertainty in the relative and absolute astrometry are 130 and < 55 mas, respectively. This table was created by the HEASARC in September 2007 based on the electronic version of Table 3 from the reference paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/vlacosmjsc
- Title:
- VLA-COSMOS Project 1.4-GHz Joint Source Catalog
- Short Name:
- VLACOSMJSC
- Date:
- 21 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- In the context of the VLA-COSMOS Deep project, additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2.5 arcseconds was used to search for sources down to 4 sigma with 1 sigma ~ 12 µJy beam<sup>-1</sup> in the central 50' x 50'. This new catalog is combined with the catalog from the Large project (obtained at 1.5" x 1.4" resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of >= 5 sigma at 1.5" and/or 2.5" resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slightly resolved at 1.5" resolution. All properties listed in the Joint catalog, such as peak flux density, integrated flux density, and source size, are determined in the 2.5" resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources. This table was created by the HEASARC in June 2010 based on the electronic version of Table 3 from the reference paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
22884. VLA-COSMOS survey. II.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/46
- Title:
- VLA-COSMOS survey. II.
- Short Name:
- J/ApJS/172/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLA-COSMOS Large Project is described and its scientific objective is discussed. We present a catalog of 3600 radio sources found in the 2deg^2^ COSMOS field at 1.4GHz. The observations in the VLA A and C configuration resulted in a resolution of 1.5"x1.4" and a mean rms noise of ~10.5(15)uJy/beam in the central 1(2)deg^2^. Eighty radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested, and the uncertainty in the relative and absolute astrometry are 130 and <55mas, respectively.
- ID:
- ivo://nasa.heasarc/vlacos324m
- Title:
- VLA-COSMOS Survey 324-MHz Continuum Source Catalog
- Short Name:
- VLACOS324M
- Date:
- 21 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source catalog based on 90-cm (324-MHz) Very Large Array (VLA) imaging of the COSMOS field, comprising a circular area of 3.14 square degrees centered on 10<sup>h</sup> 00<sup>m</sup> 28.6<sup>s</sup>, _02<sup>o</sup> 12' 21" (J2000.0 RA and Dec). The image from the merger of 3 nights of observations using all 27 VLA antennas had an effective total integration time of ~ 12 hours, an 8.0 arcsecond x 6.0 arcsecond angular resolution, and an average rms of 0.5 mJy beam<sup>-1</sup>. The extracted catalog contains 182 sources (down to 5.5 sigma), 30 of which are multi-component sources. Using Monte Carlo artificial source simulations, the authors derive the completeness of the catalog, and show that their 90-cm source counts agree very well with those from previous studies. In their paper, the authors use X-ray, NUV-NIR and radio COSMOS data to investigate the population mix of this 90-cm radio sample, and find that the sample is dominated by active galactic nuclei. The average 90-20 cm spectral index (S_nu_~ nu<sup>alpha</sup>, where S<sub>nu</sub> is the flux density at frequency nu and alpha the spectral index) of the 90-cm selected sources is -0.70, with an interquartile range from -0.90 to -0.53. Only a few ultra-steep-spectrum sources are present in this sample, consistent with results in the literature for similar fields. These data do not show clear steepening of the spectral index with redshift. Nevertheless, this sample suggests that sources with spectral indices steeper than -1 all lie at z >~ 1, in agreement with the idea that ultra-steep-spectrum radio sources may trace intermediate-redshift galaxies (z >~ 1). Using both the signal and rms maps (see Figs. 1 and 2 in the reference paper) as input data, the authors ran the AIPS task SAD to obtain a catalog of candidate components above a given local signal-to-noise ratio (S/N) threshold. The task SAD was run four times with search S/N levels of 10, 8, 6 and 5, using the resulting residual image each time. They recovered all the radio components with a local S/N > 5.00. Subsequently, all the selected components were visually inspected, in order to check their reliability, especially for the components near strong side-lobes. After a careful analysis, a S/N threshold of 5.50 was adopted as the best compromise between a deep and a reliable catalog. The procedure yielded a total of 246 components with a local S/N > 5.50. More than one component, identified in the 90-cm map sometimes belongs to a single radio source (e.g. large radio galaxies consist of multiple components). Using the 90-cm COSMOS radio map, the authors combined the various components into single sources based on visual inspection. The final catalog (contained in this HEASARC table) lists 182 radio sources, 30 of which have been classified as multiple, i.e. they are better described by more than a single component. Moreover, in order to ensure a more precise classification, all sources identified as multi-component sources have been also double-checked using the 20-cm radio map. The authors found that all the 26 multiple 90-cm radio sources within the 20-cm map have 20-cm counterpart sources already classified as multiple. The authors have made use of the VLA-COSMOS Large and Deep Projects over 2 square degrees, reaching down to an rms of ~15 µJy beam<sup>1</sup> ^ at 1.4 GHz and 1.5 arcsec resolution (Schinnerer et al. 2007, ApJS, 172, 46: the VLACOSMOS table in the HEASARC database). The 90-cm COSMOS radio catalog has, however, been extracted from a larger region of 3.14 square degrees (see Fig. 1 and Section 3.1 of the reference paper). This implies that a certain number of 90-cm sources (48) lie outside the area of the 20-cm COSMOS map used to select the radio catalog. Thus, to identify the 20-cm counterparts of the 90-cm radio sources, the authors used the joint VLA-COSMOS catalog (Schinnerer et al. 2010, ApJS, 188, 384: the VLACOSMJSC table in the HEASARC database) for the 134 sources within the 20-cm VLA-COSMOS area and the VLA- FIRST survey (White et al. 1997, ApJ, 475, 479: the FIRST table in the HEASARC database) for the remaining 48 sources. The 90-cm sources were cross-matched with the 20-cm VLA-COSMOS sources using a search radius of 2.5 arcseconds, while the cross-match with the VLA-FIRST sources has been done using a search radius of 4 arcseconds in order to take into account the larger synthesized beam of the VLA-FIRST survey of ~5 arcseconds. Finally, all the 90 cm - 20 cm associations were visually inspected in order to ensure also the association of the multiple 90-cm radio sources for which the value of the search radius used during the cross-match could be too restrictive. In summary, out of the total of 182 sources in the 90-cm catalog, 168 have counterparts at 20 cm. This table was created by the HEASARC in October 2014 based on an electronic version of Table 1 from the reference paper which was obtained from the COSMOS web site at IRSA, specifically the file vla-cosmos_327_sources_published_version.tbl at <a href="http://irsa.ipac.caltech.edu/data/COSMOS/tables/vla/">http://irsa.ipac.caltech.edu/data/COSMOS/tables/vla/</a>. This is a service provided by NASA HEASARC .
22886. V360 Lac spectroscopy
- ID:
- ivo://CDS.VizieR/J/A+A/455/1037
- Title:
- V360 Lac spectroscopy
- Short Name:
- J/A+A/455/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We include existing photometric and spectroscopic material with new observations in a detailed study of the Be+F binary V360 Lac. We used the programs FOTEL and KOREL to derive an improved linear ephemeris and to disentangle the line profiles of both binary components and telluric lines. The BINSYN software suite (described in the paper) is used to calculate synthetic light curves and spectra to fit the UBV photometry, an IUE spectrum, blue and red ground-based spectra, and observed radial-velocity curves.
22887. V441 Lac VRI light curves
- ID:
- ivo://CDS.VizieR/J/other/NewA/36.32
- Title:
- V441 Lac VRI light curves
- Short Name:
- J/other/NewA/36.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first multi-color VRI CCD light curves of a short-period eclipsing binary star v441 Lac in this paper. We obtained our light curves on Oct. 4 and 8, 2013 at Xinglong station of National Astronomical Observatories, China. We updated the ephemeris of V441 Lac based on three new minima derived by our new observational data together with previously available light curve minima. By fitting the O-C (observed minus calculated) values of the minima, we found that the orbital period of V441 Lac exhibits an increasing trend of View the dP/dt=5.67(0.35)x10^-7^days/year, which might be explained by mass transfer from the secondary component to the primary one, or angular momentum exchange by magnetic activities. We also obtained the photometric orbital parameters with the Wilson & Devinney program. Our final result shows that the V441 Lac system is a semi-detached binary with the secondary component filling roche lobe.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A13
- Title:
- VLA double-double radio galaxy candidates images
- Short Name:
- J/A+A/622/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Double-double radio galaxies (DDRGs) represent a short but unique phase in the life-cycle of some of the most powerful radio-loud active galactic nuclei (RLAGN). These galaxies display large-scale remnant radio plasma in the intergalactic medium left behind by a past episode of active galactic nuclei (AGN) activity, and meanwhile, the radio jets have restarted in a new episode. The knowledge of what causes the jets to switch off and restart is crucial to our understanding of galaxy evolution, while it is important to know if DDRGs form a host galaxy dichotomy relative to RLAGN. The sensitivity and field of view of LOFAR enables the observation of DDRGs on a population basis rather than single-source observations. Using statistical comparisons with a control sample of RLAGN, we may obtain insights into the nature of DDRGs in the context of their host galaxies, where physical differences in their hosts compared to RLAGN as a population may allow us to infer the conditions that drive restarting jets. We utilised the LOFAR Two-Metre Sky Survey (LoTSS) DR1, using a visual identification method to compile a sample of morphologically selected candidate DDRGs, showing two pairs of radio lobes. To confirm the restarted nature in each of the candidate sources, we obtained follow-up observations with the Karl. G. Jansky Very Large Array (VLA) at higher resolution to observe the inner lobes or restarted jets, the confirmation of which created a robust sample of 33 DDRGs.We created a comparison sample of 777 RLAGN, matching the luminosity distribution of the DDRG sample, and compared the optical and infrared magnitudes and colours of their host galaxies. We find that there is no statistically significant difference in the brightness of the host galaxies between double-doubles and single-cycle RLAGN. The DDRG and RLAGN samples also have similar distributions in WISE mid-infrared colours, indicating similar ages of stellar populations and dust levels in the hosts of DDRGs. We conclude that DDRGs and 'normal' RLAGN are hosted by galaxies of the same type, and that DDRG activity is simply a normal part of the life cycle of RLAGN. Restarted jets, particularly for the class of low-excitation radio galaxies, rather than being a product of a particular event in the life of a host galaxy, must instead be caused by smaller scale changes, such as in the accretion system surrounding the black hole.
- ID:
- ivo://nasa.heasarc/vlaen20cm
- Title:
- VLA ELAIS N1, N2, N3 Fields 20-cm Source Catalog
- Short Name:
- VLAEN20CM
- Date:
- 21 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors have used the Very Large Array (VLA) in C configuration to carry out a sensitive 20-cm radio survey of regions of the sky that have been surveyed in the far-infrared (FIR) over the wavelength range 5 -200 microns (µm) with ISO (Infrared Space Observatory) as part of the European Large-Area ISO Survey (ELAIS). As usual in surveys based on a relatively small number of overlapping VLA pointings, the flux limit varies over the area surveyed: from a 5-sigma limit of 0.135 mJy over an area of 0.12 deg<sup>2</sup> to 1.15 mJy or better over the whole region covered of 4.22 deg<sup>2</sup>. In their paper, the authors present the complete radio catalog of 867 sources, 428 of which form a complete sample in the flux range 0.2 - 1.0 mJy. These regions of the sky have previously been surveyed to shallower flux limits at 20 cm with the VLA as part of the VLA D-configuration NVSS (full width at half-maximum, FWHM = 45arcseconds) and VLA-B configuration FIRST (FWHM = 5 arcseconds) surveys. This whole survey has a nominal 5-sigma flux limit a factor of 2 below that of the NVSS; 3.4 deg<sup>2</sup> of the survey reaches the nominal flux limit of the FIRST survey and 1.5 deg<sup>2</sup> reaches 0.25 mJy, a factor of 4 below the nominal FIRST survey limit. In addition, this survey is at a resolution intermediate between the two surveys and thus is well suited for a comparison of the reliability and resolution-dependent surface brightness effects that affect interferometric radio surveys. The authors have carried out a detailed comparison of their survey and these two independent surveys in order to assess the reliability and completeness of each. Considering the whole sample, they found that to the 5-sigma nominal limits of 2.3 and 1.0 mJy, respectively, the NVSS and FIRST surveys have a completeness of 96<sup>+2</sup><sub>-3</sub> and 89<sup>+2</sup><sub>-3</sub> % and a reliability of 99<sup>+1</sup><sub>-2</sub> and 94<sup>+2</sup><sub>-2</sub> %. The radio observations were obtained of three ISO ELAIS survey regions in the Northern celestial hemisphere (N1 1610+5430, N2 1636+4115 and N3 1429+3306) (see Table 1 of the reference paper for the details of the fields and the individual pointings). The observations are made with the Very Large Array (VLA) radio telescope at 1.4 GHz (20 cm) in the VLA C configuration (maximum baseline 3.4 km) with an angular resolution (FWHM) of ~15 arcseconds. The aim of these VLA observations was to obtain uniform coverage of the ELAIS regions with an rms noise limit of ~50 microJansky (µJy). This table contains the 921 components of 867 total sources detected at a level of >= 5 sigma (44 of which are multiple component sources as defined in Section 4.3 of the reference paper) over a total area of 4.222 deg<sup>2</sup>. There are also entries describing the properties of the total sources for the 44 multi-component sources (for which the positions have been computed as the flux-weighted average positions of their components), and thus this catalog contains 965 (921 + 44) entries. To filter out the latter, component_id values != 'T' should be selected when searching this table. This table was originally ingested by the HEASARC in August 2012, based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/302/222">CDS Catalog J/MNRAS/302/222</a> file table3.dat. It was last updated in September 2013 to remove a duplicate entry for the source ELAISR J142743+331323. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/vlaecdfscls
- Title:
- VLA Extended-Chandra Deep Field-South Classification Catalog
- Short Name:
- VLAECDFSCLS
- Date:
- 21 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The sub-mJy radio population is a mixture of active systems, that is star-forming galaxies (SFGs) and active galactic nuclei (AGNs). In their paper, the authors study a sample of 883 radio sources detected at 1.4 GHz in a deep Very Large Array (VLA) survey of the Extended Chandra Deep Field-South (E-CDF-S) that reaches a best rms sensitivity of 6 microJansky (µJy). The authors have used a simple scheme to disentangle SFGs, radio-quiet (RQ), and radio-loud (RL) AGNs based on the combination of radio data with Chandra X-ray data and mid-infrared observations from Spitzer. They find that at flux densities between about 30 and 100 uJy, the radio population is dominated by SFGs (~60%) and that RQ AGNs become increasingly important over RL ones below 100 uJy. In the paper, the authors also compare the host galaxy properties of the three classes in terms of morphology, optical colors and stellar masses. Their results show that both SFG and RQ AGN host galaxies have blue colors and late-type morphology while RL AGNs tend to be hosted by massive red galaxies with early-type morphology. This supports the hypothesis that radio emission in SFGs and RQ AGNs mainly comes from the same physical process: star formation in the host galaxy. This table was created by the HEASARC in January 2014 based on the machine-readable version of Table 1 from the reference paper which was obtained from the MNRAS web site. This is a service provided by NASA HEASARC .
