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501. Faint red galaxies in Coma cluster spectroscopy
ID:
ivo://CDS.VizieR/J/MNRAS/392/1265
Title:
Faint red galaxies in Coma cluster spectroscopy
Short Name:
J/MNRAS/392/1265
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the stellar populations in a sample of 89 faint red galaxies in the Coma cluster, using high signal-to-noise ratio (S/N) spectroscopy from the 6.5-m MMT. Our sample is drawn from two 1{deg} fields, one centred on the cluster core and the other located 1{deg} to the south-west of the cluster centre. The target galaxies are mostly 2-4mag fainter than M*; galaxies with these luminosities have been previously studied only using small samples, or at low S/N. For a comparison sample we use published high-S/N data for red-sequence galaxies in the Shapley supercluster. We use state-of-the-art stellar population models (by R. Schiavon, Cat. <J/ApJS/171/146>) to interpret the absorption-line indices and infer the single-burst-equivalent age and metallicity (Fe/H) for each galaxy, as well as the abundances of the light elements Mg, Ca, C and N.
502. Far-infrared emission from 5 galaxy clusters
ID:
ivo://CDS.VizieR/J/ApJ/405/94
Title:
Far-infrared emission from 5 galaxy clusters
Short Name:
J/ApJ/405/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analyzed IRAS image data using a random position, multiple-aperture photometry method to study diffuse far-infrared emission for a sample of 56 clusters of galaxies at 60 and 100um. Five of the clusters in the sample exhibit excess far-infrared emission, but at low levels of significance. For A496 (Perseus) and MKW 1, this emission appears to be associated with a strong point source: in A2344, the observed excess is probably due to a foreground cirrus cloud. Two clusters, A262 and A2670, show evidence for extended diffuse emission. This emission is unlikely to be due to point sources associated with the clusters. In these two clusters, the diffuse emission shows evidence of being extended along the cluster's major axis. Far-infrared maps at 60 and 100um are presented for these five clusters. We find that contamination due to diffuse Galactic cirrus represents the major source of uncertainty in the measurement of far-infrared emission. The mean cluster fluxes for the sample as a whole are 44 and 107mJy for a 4' diameter aperture at 60 and 100um, respectively. The corresponding fluxes for a 10' diameter aperture are 138 and 253mJy at 60 and 100um. Photometry for the entire sample shows statistical evidence for excess emission at 60um associated with clusters in apertures 4' and 10' in diameter. This result is unlikely to be caused by random sampling errors. The flux distributions are analyzed for evidence that excess far-infrared radiation correlates with cluster environmental characteristics. Although we find evidence that poorer X-ray clusters are stronger far-infrared emitters, this result is tentative owing to the small sample sizes involved. The far-infrared luminosities, dust temperatures, and dust masses which these results imply are also presented. Finally, the origin and possible heating mechanism for dust in the intracluster medium is discussed.
503. Far-UV excess object survey
ID:
ivo://CDS.VizieR/J/A+A/250/370
Title:
Far-UV excess object survey
Short Name:
J/A+A/250/370
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical spectra have been obtained for a selection of objects included in a catalog of far ultraviolet bright, high galactic latitude objects detected with a balloon-borne survey telescope. The observed objects provide a sample of subdwarf O and B stars, white dwarfs, and binary systems including a hot sub-luminous member. Model atmospheres analysis of the sub-dwarf sample is used to determine the temperature, gravity, and helium to hydrogen ratio of the individual objects. A smooth distribution of objects is found on the gravity versus temperature diagram near the theoretical location of the extended horizontal branch. A break between the helium rich and helium poor objects occurs at 40000K. Suspected binary objects were found and analyzed to determine the temperature and gravity of the hot subluminous member in each system. The number of subdwarf stars contained in binaries is determined to be from 65% to 100%. The number versus ultraviolet magnitude distribution of the subdwarf B sample is modeled to obtain a midplane density of 3.3x10^-6^pc^-3^ and a population scale height of 240pc. The proportion of white dwarfs that experience the subdwarf phase of evolution is found to be 0.94%.
504. Far-UV spectral atlas of O-type stars
ID:
ivo://CDS.VizieR/J/ApJS/202/17
Title:
Far-UV spectral atlas of O-type stars
Short Name:
J/ApJS/202/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we present a spectral atlas covering the wavelength interval 930-1188{AA} for O2-O9.5 stars using Far-Ultraviolet Spectroscopic Explorer archival data. The stars selected for the atlas were drawn from three populations: Galactic main-sequence (classes III-V) stars, supergiants, and main-sequence stars in the Magellanic Clouds, which have low metallicities. For several of these stars, we have prepared FITS files comprised of pairs of merged spectra for user access via the Multimission Archive at Space Telescope (MAST). We chose spectra from the first population with spectral types O4, O5, O6, O7, O8, and O9.5 and used them to compile tables and figures with identifications of all possible atmospheric and interstellar medium lines in the region 949-1188{AA}. Our identified line totals for these six representative spectra are 821 (500), 992 (663), 1077 (749), 1178 (847), 1359 (1001), and 1798 (1392) lines, respectively, where the numbers in parentheses are the totals of lines formed in the atmospheres, according to spectral synthesis models. The total number of unique atmospheric identifications for the six main-sequence O-star template spectra is 1792, whereas the number of atmospheric lines in common to these spectra is 300. The number of identified lines decreases toward earlier types (increasing effective temperature), while the percentages of "missed" features (unknown lines not predicted from our spectral syntheses) drop from a high of 8% at type B0.2, from our recently published B-star far-UV atlas (Cat. J/ApJS/186/175), to 1%-3% for type O spectra. The percentages of overpredicted lines are similar, despite their being much higher for B-star spectra.
505. Far-UV spectra of Galactic corona sight lines
ID:
ivo://CDS.VizieR/J/ApJ/749/157
Title:
Far-UV spectra of Galactic corona sight lines
Short Name:
J/ApJ/749/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the properties of the transition temperature (T~10^5^K) gas in the Milky Way corona, based on the measurements of OVI, NV, CIV, SiIV, and FeIII absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60km/s. On average the integrated column densities are logN(OVI)=14.3, logN(NV)=13.5, logN(CIV)=14.2, logN(SiIV)=13.6, and logN(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor ~2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions.
506. Far-UV spectra of PN central stars
ID:
ivo://CDS.VizieR/J/A+A/553/A126
Title:
Far-UV spectra of PN central stars
Short Name:
J/A+A/553/A126
Date:
21 Oct 2021
Publisher:
CDS
Description:
The occurrence of stellar wind in the central star of a planetary nebula (CSPN) can be revealed by the presence of P Cygni profiles of high-excitation lines overimposed on its stellar continuum. We have examined the entire Far-Ultraviolet Spectroscopic Explorer FUSE archive and merged all useful spectroscopic observations of CSPNe to produce the highest quality spectra that can be used to assess the occurrence of stellar winds. Furthermore, the individual spectra of each CSPN have been compared to search for variability in the P Cygni profile. P Cygni profiles of high-excitation lines have been found in 44 CSPNe, with a clear correlation between the ionization potential of the lines and the effective temperature of the star.
507. Far-UV spectroscopic atlas of B stars
ID:
ivo://CDS.VizieR/J/ApJS/186/175
Title:
Far-UV spectroscopic atlas of B stars
Short Name:
J/ApJS/186/175
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have constructed a detailed spectral atlas covering the wavelength region 930-1225{AA} for 10 sharp-lined B0-B9 stars near the main sequence. Most of the spectra we assembled are from the archives of the Far Ultraviolet Spectroscopic Explorer satellite, but for nine stars, wavelength coverage above 1188{AA} was taken from high-resolution International Ultraviolet Explorer or echelle Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra. To represent the tenth star at type B0.2V, we used the Copernicus atlas of tau Sco. We made extensive line identifications in the region 949-1225{AA} of all atomic features having published oscillator strengths at types B0, B2, and B8. These are provided as a supplementary data product-hence the term detailed atlas. Our list of found features totals 2288, 1612, and 2469 lines, respectively. We were able to identify 92%, 98%, and 98% of these features with known atomic transitions with varying degrees of certainty in these spectra. The remaining lines do not have published oscillator strengths. Photospheric lines account for 94%, 87%, and 91%, respectively, of all our identifications, with the remainder being due to interstellar (usually molecular H2) lines. We also discuss the numbers of lines with respect to the distributions of various ions for these three most studied spectral subtypes. A table is also given of 162 least blended lines that can be used as possible diagnostics of physical conditions in B star atmospheres.
508. Far-UV spectroscopy of T Tau stars
ID:
ivo://CDS.VizieR/J/ApJ/744/121
Title:
Far-UV spectroscopy of T Tau stars
Short Name:
J/ApJ/744/121
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a far-ultraviolet (FUV) spectral atlas consisting of spectra of 91 pre-main-sequence stars. Most stars in this sample were observed with the Space Telescope Imaging Spectrograph and Advanced Camera for Surveys on the Hubble Space Telescope (HST). A few archival spectra from the International Ultraviolet Explorer and the Goddard High Resolution Spectrograph on HST are included for completeness. We find strong correlations among the OI{lambda}1304 triplet, the SiIV {lambda}{lambda}1394/1403 doublet, the CIV{lambda}1549 doublet, and the HeII {lambda}1640 line luminosities. For classical T Tauri stars (CTTSs), we also find strong correlations between these lines and the accretion luminosity, suggesting that these lines form in processes related to accretion. These FUV line fluxes and X-ray luminosity correlate loosely with large scatters. The FUV emission also correlates well with H{alpha}, H{beta}, and CaII K line luminosities. These correlations between FUV and optical diagnostics can be used to obtain rough estimates of FUV line fluxes from optical observations. Molecular hydrogen (H_2_) emission is generally present in the spectra of actively accreting CTTSs but not the weak-lined T Tauri stars that are not accreting. The presence of H_2_ emission in the spectrum of HD 98800N suggests that the disk should be classified as actively accreting rather than a debris disk.
509. -2.6<=[Fe/H]<=0.2 F and G dwarfs. II. Abundances
ID:
ivo://CDS.VizieR/J/ApJ/833/225
Title:
-2.6<=[Fe/H]<=0.2 F and G dwarfs. II. Abundances
Short Name:
J/ApJ/833/225
Date:
21 Oct 2021
Publisher:
CDS
Description:
For the first time, we present an extensive study of stars with individual non-LTE (NLTE) abundances for 17 chemical elements from Li to Eu in a sample of stars uniformly distributed over the -2.62<=[Fe/H]<=+0.24 metallicity range that is suitable for the Galactic chemical evolution research. The star sample has been kinematically selected to trace the Galactic thin and thick disks and halo. We find new results and improve earlier ones as follows: (i) the element-to-iron ratios for Mg, Si, Ca, and Ti form a metal-poor (MP) plateau at a similar height of 0.3 dex, and the knee occurs at common [Fe/H]~-0.8. The knee at the same metallicity is observed for [O/Fe], and the MP plateau is formed at [O/Fe]=0.61. (ii) The upward trend of [C/O] with decreasing metallicity exists at [Fe/H]<-1.2, supporting the earlier finding of Akerman et al. (iii) An underabundance of Na relative to Mg in the [Fe/H]<-1 stars is nearly constant, with the mean [Na/Mg]~-0.5. (iv) The K/Sc, Ca/Sc, and Ti/Sc ratios form well-defined trends, suggesting a common site of the K-Ti production. (v) Sr follows the Fe abundance down to [Fe/H]~-2.5, while Zr is enhanced in MP stars. (vi) The comparisons of our results with some widely used Galactic evolution models are given. The use of the NLTE element abundances gives increased credit to the interpretation of the data in the context of the chemical evolution of the Galaxy.
510. FeII emission in quasars
ID:
ivo://CDS.VizieR/J/ApJ/687/78
Title:
FeII emission in quasars
Short Name:
J/ApJ/687/78
Date:
21 Oct 2021
Publisher:
CDS
Description:
Broad FeII emission is a prominent feature of the optical and ultraviolet spectra of quasars. We report on a systematical investigation of optical FeII emission in a large sample of 4037 z<0.8 quasars selected from the SDSS-DR5 quasar catalog (Cat. VII/252). We have developed and tested a detailed line-fitting technique, taking into account the complex continuum and narrow and broad emission-line spectra. Our primary goal is to quantify the velocity broadening and velocity shift of the FeII spectrum in order to constrain the location of the FeII-emitting region and its relation to the broad-line region. We find that the majority of quasars show FeII emission that is redshifted, typically by ~400km/s, but up to 2000km/s, with respect to the systemic velocity of the narrow-line region or of the conventional broad-line region as traced by the H{beta} line. Moreover, the line width of FeII is significantly narrower than that of the broad component of H{beta}. We show that the magnitude of the FeII redshift correlates inversely with the Eddington ratio, and that there is a tendency for sources with redshifted FeII emission to show red asymmetry in the H{beta} line. These characteristics strongly suggest that FeII originates from a location different from, and most likely exterior to, the region that produces most of H{beta}. The FeII-emitting zone traces a portion of the broad-line region of intermediate velocities whose dynamics may be dominated by infall.