- ID:
- ivo://CDS.VizieR/J/A+A/402/37
- Title:
- UV to radio SED of galaxies in Virgo cluster
- Short Name:
- J/A+A/402/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies (>=S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of H{alpha}, CO and HI lines, homogeneously reduced, obtained from our own observations or compiled from the literature. Assuming the energy balance between the absorbed stellar light and that radiated in the IR by dust, we calibrate an empirical attenuation law suitable for correcting photometric and spectroscopic data of normal galaxies. The data, corrected for internal extinction, are used to construct the spectral energy distribution (SED) of each individual galaxy, and combined to trace the median SED of galaxies in various classes of morphological type and luminosity.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AZh/72/291
- Title:
- Variability at Frequencies 3.9 and 7.5 GHz
- Short Name:
- J/AZh/72/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete sample of radio sources from the Zelenchukskii survey with fluxes S(3.9GHz)>200mJy and declination range from +4 till +6 degrees were observed at 3.9 and 7.5GHz over the course of seven years. There are one hundred and eighty radio sources in the sample.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A107
- Title:
- Variability of 198 extragalactic radio sources
- Short Name:
- J/A+A/553/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining measurements taken using the Wilkinson Microwave Anisotropy Probe (WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to 2010, we investigate the long-term flux density variability of extragalactic radio sources selected from the Planck Early Release Compact Source Catalogue. The single-year, single-frequency WMAP maps are used to estimate yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33GHz), Q (41GHz), V (61GHz), and W (94GHz). We identify 82, 67, 32, and 15 sources respectively as variable at greater than 99% confidence level in these four bands. The amplitudes of variation are comparable between bands, and are not correlated with either the flux densities or the spectral indices of the sources. The number counts of WMAP Ka-band sources are stable from year to year despite the fluctuation caused by individual source variability. Most of our sources show strong correlation in variability between bands. Almost all the sources that show variability are blazars. We have attempted to fit two simple, four-parameter models to the time-series of 32 sources showing correlated variability at multiple frequencies - a long-term flaring model and a rotating-jet model. We find that 19 sources (60%) can be fit with the simple rotating-jet model, and ten of these also fit the simple long-term flaring model. The remaining 13 sources (40%) show more complex variability behaviour that is not consistent with either model. Extended radio galaxies in our sample show no sign of variability, as expected, with the exception of Pictor A for which we report evidence for a millimetre flare lasting between 2002 and 2010.
- ID:
- ivo://CDS.VizieR/J/A+A/370/468
- Title:
- Variability of gamma-ray sources
- Short Name:
- J/A+A/370/468
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of 40 low-latitude unidentified 3EG gamma-ray sources which were found to be not positionally coincident with any known class of potential gamma-ray emitters in the Galaxy (Romero et al., 1999A&A...348..868R). We have performed a variability analysis which reveals that many of these 40 sources are variable. These sources have, in addition, a steep mean value of the gamma-ray spectral index, <{Gamma}>=2.41+/-0.2, which, combined with the high level of variability, seems to rule out a pulsar origin. The positional coincidences with uncatalogued candidates to supernova remnants were also studied. Only 7 sources in the sample are spatially coincident with these candidates, a result that is shown to be consistent with the expected level of pure chance association. A complementary search for weak radio counterparts was also conducted and the results are presented as an extensive table containing all significant point-like radio sources within the 40 EGRET fields. We argue that in order to produce the high variability, steep gamma-ray spectra, and absence of strong radio counterparts observed in some of the gamma-ray sources of our sample, a new class of objects should be postulated, and we analyze a viable candidate.
- ID:
- ivo://CDS.VizieR/J/AJ/137/5022
- Title:
- Variability of radio-bright BL Lac objects
- Short Name:
- J/AJ/137/5022
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio-bright BL Lacertae objects (BLOs) are typically very variable and exhibit prominent flaring. We use a sample of 24 BLOs, regularly monitored at Metsahovi Radio Observatory, to get a clear idea of their flaring behavior in the radio domain and to find possible commonalities in their variability patterns. Our goal was to compare the results given by computational timescales and the observed variability parameters determined directly from the flux curves. Also, we wanted to find out if the BLO flares adhere to the generalized shock model, which gives a schematic explanation for the physical process giving rise to the variability. We use long-term monitoring data from 4.8, 8, 14.5, 22, 37, 90, and 230GHz, obtained mainly from the University of Michigan and Metsahovi Radio Observatories. The structure function, discrete correlation function, and Lomb-Scargle periodogram timescales, calculated in a previous study, are analyzed in more detail. Also, we determine flare durations, rise and decay times, and absolute and relative peak fluxes from the monitoring data.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/49
- Title:
- Variable and transient radio sources in FIRST
- Short Name:
- J/ApJ/742/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A comprehensive search for variable and transient radio sources has been conducted using ~55000 snapshot images of the Faint Images of the Radio Sky at Twenty-cm survey (Cat. VIII/90). We present an analysis leading to the discovery of 1627 variable and transient objects down to mJy levels over a wide range of timescales (a few minutes to years). Variations observed range from 20% to a factor of 25. Multi-wavelength matching for counterparts reveals the diverse classes of objects exhibiting variability, ranging from nearby stars and pulsars to galaxies and distant quasars. Interestingly, more than half of the objects in the sample have either no classified counterparts or no corresponding sources at any other wavelength and require multi-wavelength follow-up observations. We discuss these classes of variables and speculate on the identity of objects that lack multi-wavelength counterparts.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/45
- Title:
- Variable 1.4GHz radio sources from NVSS and FIRST
- Short Name:
- J/ApJ/737/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We augment the two widest/deepest 1.4GHz radio surveys, the NRAO VLA Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimeters (FIRST), with the mean epoch in which each source was observed. We use these catalogs to search for unresolved sources that vary between the FIRST and NVSS epochs. We find 43 variable sources (0.1% of the sources) that vary by more than 4{sigma}, and we construct the mean structure function of these objects. This enables us to explore radio variability on timescales between several months and about five years. We find that, on these timescales, the mean structure function of the variable sources is consistent with a flat structure function. A plausible explanation to these observations is that a large fraction of the variability at 1.4GHz is induced by scintillations in the interstellar medium, rather than by intrinsic variability. Finally, for a subsample of the variables for which the redshift is available, we do not find strong evidence for a correlation between the variability amplitude and the source redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/622/187
- Title:
- Velocity of eight RASSCALS galaxy groups
- Short Name:
- J/ApJ/622/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the distribution of gas pressure and entropy in eight groups of galaxies belonging to the ROSAT All-Sky Survey/Center for Astrophysics Loose Systems (RASSCALS, Cat. <J/ApJ/534/114>). We use archival and proprietary XMM-Newton observations, supplementing the X-ray data with redshifts derived from the literature; we also list 125 new redshifts measured with the Gemini North telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2487
- Title:
- VERA 22GHz Fringe Search Survey
- Short Name:
- J/AJ/133/2487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents results of a survey search for bright compact radio sources at 22GHz with the VERA radio interferometer. Each source from a list of 2494 objects was observed in one scan for 2 minutes. The purpose of this survey was to find compact extragalactic sources bright enough at 22GHz to be useful as phase calibrators. Observed sources were either (1) within 6{deg} of the Galactic plane, or (2) within 11{deg} of the Galactic center, or (3) within 2{deg} of known water masers. Among the observed sources, 549 were detected, including 180 extragalactic objects that were not previously observed with the very long baseline interferometry technique. Estimates of the correlated flux densities of the detected sources are presented. It was found that the probability of detecting a 200mJy source with 120s of integration time is 60%.
- ID:
- ivo://CDS.VizieR/J/MNRAS/360/340
- Title:
- Very Small Array. Flux density at 33GHz
- Short Name:
- J/MNRAS/360/340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the source subtraction strategy and observations for the extended Very Small Array (VSA), a cosmic microwave background interferometer operating at 33GHz. A total of 453 sources were monitored at 33GHz using a dedicated source subtraction baseline. 131 sources brighter than 20mJy were directly subtracted from the VSA visibility data. Some characteristics of the subtracted sources, such as spectra and variability, are discussed. The 33GHz source counts are estimated from a sample selected at 15GHz. The selection of VSA fields in order to avoid bright sources introduces a bias into the observed counts. This bias is corrected and the resulting source count is estimated to be complete in the flux-density range 20114mJy. The 33GHz source counts are used to calculate a correction to the VSA power spectrum for sources below the subtraction limit.
