- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1098
- Title:
- UV-upturn of elliptical galaxies model
- Short Name:
- J/MNRAS/380/1098
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A long-standing problem in the study of elliptical galaxies is the far-ultraviolet (FUV) excess in their spectra (also known as UV-upturn, UV rising-branch, UV rising flux, or UVX). While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes. We have developed an evolutionary population synthesis (EPS) model for the FUV excess of elliptical galaxies based on the binary model of Han et al. (2002MNRAS.336..449H and 2003MNRAS.341..669H) for the formation of hot subdwarfs in our Galaxy. We give the colour evolution of a simple stellar population (SSP) (including binaries) of 10^10^M_{sun}_ for our standard simulation set. We have also compiled a file for the SED evolution, in which the SEDs without binary interactions are also supplied.
- ID:
- ivo://CDS.VizieR/J/A+AS/121/461
- Title:
- UV variability of Fairall-9
- Short Name:
- J/A+AS/121/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a study of the UV variability of the galaxy Fairall-9 between 1978 and 1991. Table 1 shows the UV continuum fluxes measured in three "line-free" windows centered at 1171, 1400 and 1910 A (observed wavelengths), and corrected for E(B-V)=0.035 extinction. The IUE Fine Error Sensor (FES) counts (optical photometry) are also given in this table, corrected for the same extinction. Tables 10, 11, 12 and 13 show the variability of the components for the main UV lines (Ly{alpha}+NV, SiIV, CIV and MgII). Line profile variability has been used to isolate four gaussian line components, which are sufficient to describe all lines at all levels of brightness in a consistent way: one narrow (i.e. unresolved at the IUE resolution) and three broad components: a central (velocity same as the narrow line), a redshifted (v=3300 km/s) and a blue shifted one (v=-3600 km/s). The Ly{alpha}-NV blend is fitted together in the Ly{alpha} region (Table 10), to account the NV presence (one narrow and one red component). The results for SiIV are shown in Table 11. In CIV (Table 12) have been included a very weak component bluer than the blue component, most likely associated with NIV] 1486. Table 13 shows MgII results.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1137
- Title:
- UV, VIH photometry of NGC 1311
- Short Name:
- J/AJ/140/1137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extracted point-spread-function-fitted stellar photometry from near-ultraviolet, optical, and near-infrared images, obtained with the Hubble Space Telescope, of the nearby (D~5.5Mpc) SBm galaxy NGC 1311. The ultraviolet and optical data reveal a population of hot main-sequence (MS) stars with ages of 2-10Myr. We also find populations of blue supergiants with ages between 10 and 40Myr and red supergiants with ages between 10 and 100Myr.
- ID:
- ivo://CDS.VizieR/J/other/RAA/14.1251
- Title:
- Variability of bright X-ray point sources
- Short Name:
- J/other/RAA/14.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present long term optical variability studies of bright X-ray sources in four nearby elliptical galaxies with the Chandra Advanced CCD Imaging Spectrometer array (ACIS-S) and observations from the Hubble Space Telescope (HST) Advanced Camera for Surveys. Out of the 46 bright (X-ray counts >60) sources that are in the common field of view of the Chandra and HST observations, 34 of them have potential optical counterparts, while the rest of them are optically dark. After taking into account systematic errors, estimated using optical sources in the field as a reference, we find that four of the X-ray sources (three in NGC 1399 and one in NGC 1427) have variable optical counterparts at a high level of significance. The X-ray luminosities of these sources are ~10^38^erg/s and are also variable on similar time scales. The optical variability implies that the optical emission is associated with the X-ray source itself rather than being the integrated light from a host globular cluster. For one source, the change in optical magnitude is >0.3, which is one of the highest reported for this class of X-ray sources and this suggests that the optical variability is induced by the X-ray activity. However, the optically variable sources in NGC 1399 have been reported to have blue colors (g-z>1). All four sources have been detected in the infrared (IR) by Spitzer as point sources, and their ratios of 5.8 to 3.6um flux are >0.63, indicating that their IR spectra are like those of Active Galactic Nuclei (AGNs). While spectroscopic confirmation is required, it is likely that all four sources are background AGNs. We find none of the X-ray sources having optical/IR colors different from AGNs to be optically variable.
- 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.
4017. Variables in M33
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1405
- Title:
- Variables in M33
- Short Name:
- J/MNRAS/371/1405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a variability survey of the Local Group galaxy M33, using g', r', and i' observations from 27 nights spanning 17 months, made with the MegaPrime/MegaCam instrument on the 3.6m CFHT telescope (Canada-France-Hawaii Telescope). We identify more than 36000 variable sources with g', r', i'<~24, out of approximately two million point sources in a 1-deg^2^ field of view. This increases the number of known variables in this galaxy by more than a factor of 20. In this paper, we provide a brief description of the data and a general overview of the variable star population which includes more than 1300 candidate variable blue and red supergiant stars, more than 2000 Cepheids, and more than 19000 long-period variable asymptotic giant branch and red giant branch stars.
4018. Variable stars in Cen A
- ID:
- ivo://CDS.VizieR/J/A+A/478/755
- Title:
- Variable stars in Cen A
- Short Name:
- J/A+A/478/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Difference imaging has proven to be a powerful technique for detecting and monitoring the variability of unresolved stellar sources in M 31. Using this technique in surveys of galaxies outside the Local Group could have many interesting applications. The goal of this paper is to test difference imaging photometry on Centaurus A, the nearest giant elliptical galaxy, at a distance of 4Mpc. We obtained deep photometric data with the Wide Field Imager at the ESO/MPG 2.2m at La Silla spread over almost two months. Applying the difference imaging photometry package DIFIMPHOT, we produced high-quality difference images and detected variable sources. The sensitivity of the current observational setup was determined through artificial residual tests. In the resulting high-quality difference images, we detect 271 variable stars. We find a difference flux detection limit corresponding to m_R_~=24.5. Based on a simple model of the halo of Centaurus A, we estimate that a ground-based microlensing survey would detect in the order of 4 microlensing events per year due to lenses in the halo. Conclusions: Difference imaging photometry works very well at the distance of Centaurus A and promises to be a useful tool for detecting and studying variable stars in galaxies outside the local group. For microlensing surveys, a higher sensitivity is needed than achieved here, which would be possible with a large ground-based telescope or space observatory with wide-field imaging capabilities.
- ID:
- ivo://CDS.VizieR/J/ApJ/674/L81
- Title:
- Variable stars in dwarf galaxy CVn I
- Short Name:
- J/ApJ/674/L81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 23 RR Lyrae stars and three possible anomalous Cepheids (ACs) among 84 candidate variables in the recently discovered Canes Venatici I (CVn I) dwarf spheroidal galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/121
- Title:
- Variable stars in Her dwarf galaxy
- Short Name:
- J/ApJ/756/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first time-series study of the ultra-faint dwarf galaxy Hercules. Using a variety of telescope/instrument facilities we secured about 50 V and 80 B epochs. These data allowed us to detect and characterize 10 pulsating variable stars in Hercules. Our final sample includes six fundamental-mode (ab-type) and three first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The average period of the ab-type RR Lyrae stars, <P_ab_>=0.68days ({sigma}=0.03days), places Hercules in the Oosterhoff II group, as found for almost the totality of the ultra-faint dwarf galaxies investigated so far for variability. The RR Lyrae stars were used to obtain independent estimates of the metallicity, reddening, and distance to Hercules, for which we find [Fe/H]=-2.30+/-0.15dex, E(B-V)=0.09+/-0.02mag, and (m-M)_0_=20.6+/-0.1mag, in good agreement with the literature values. We have obtained a V, B-V color-magnitude diagram (CMD) of Hercules that reaches V~25mag and extends beyond the galaxy's half-light radius over a total area of 40'x36'. The CMD and the RR Lyrae stars indicate the presence of a population as old and metal-poor as (at least) the Galactic globular cluster M68.
