- ID:
- ivo://CDS.VizieR/J/A+AS/132/181
- Title:
- Very luminous IRAS galaxies spectra. II.
- Short Name:
- J/A+AS/132/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations of a sample of 73 very luminous IRAS galaxies (log(L_IR_/L_{sun}_)>=11.5 for H_0_=50km/s/Mpc, q_0_=0.5) from the 2Jy redshift survey catalogue were carried out using the 2.16m telescope at the Beijing Astronomical Observatory. The observational data, including the optical images (extracted from Digital Sky Survey) and spectra for these galaxies, are presented in paper I (Wu et al., 1998, Cat. <J/A+AS/127/521>). In this paper, we give the spectral and morphological classifications for these very luminous IRAS galaxies (VLIRGs). We show that about 60% of VLIRGs exhibit AGN-like spectra (Seyfert 1s, Seyfert 2s, LINER-like galaxies). This fraction goes up to 82% for the ultraluminous IRAS galaxies (ULIRGs) subsample (Log(L_IR_/ L_{sun}_)>=12.0). 56% of the VLIRGs show strong interaction or merging signatures; this fraction rises to 91% for the ULIRGs. These statistical results strongly suggest that interaction triggers nuclear activities and enhances the infrared luminosity. We find that LINER and a mixture type which have optical properties of both HII galaxies and LINERs could be at the transition stage from infrared luminous HII galaxies to AGNs; their main energy production is from starbursts as well as AGNs. Both infrared luminosities and Ha equivalent widths increase dramatically as nuclear separations between VLIRGs and their nearest neighbors decrease. There is little doubt that strong starbursts happen in the nuclei of VLIRGs. Assuming class 0 as advanced merger, we construct a simple merger sequence, from morphological classes 1 to 4 (with near or far companions), to class 5 and 6 (interacting pairs and mergers) and then to class 0 (isolated galaxies). Along this sequence, VLIRGs evolve from HII galaxies to AGNs.
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- ID:
- ivo://CDS.VizieR/J/A+A/608/A89
- Title:
- Very metal poor stars in MW halo
- Short Name:
- J/A+A/608/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, -4<=[Fe/H]<~-2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo. Our results are based on high-resolution spectroscopic datasets and homogeneous and accurate atmospheric parameters determined in Paper I. We show that once the NLTE effects are properly taken into account, all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [alpha/Fe]=0.3 for each of the alpha-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in alpha/Fe with increasing metallicity in the Bootes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. We show that Sr in the massive galaxies is better correlated with Mg than Fe and that its origin is essentially independent of Ba, for most of the [Ba/H] range. Our three UFDs, that is Bootes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg]=-1.3 and [Ba/Mg]=-1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Bootes I and UMa II indicate a common r-process origin of their neutron-capture elements. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H]<-2, is the strongest.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/1791
- Title:
- Very young galaxies from SDSS
- Short Name:
- J/MNRAS/492/1791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Only a handful of galaxies in the local Universe appear to be very young. We estimate the fraction of very young galaxies (VYGs), defined as those with more than half their stellar masses formed within the last Gyr. We fit non-parametric star formation histories (SFHs) to ~280000 galaxy spectra from a flux- and volume-limited subsample of the Main Galaxy Sample (MGS) of the SDSS, which is also complete in mass-to-light ratio, thus properly accounting for passive galaxies of a given mass. The VYG fractions decrease with increasing galaxy stellar mass, from ~50 per cent at m=10^8^M_{sun}_ to ~0.1 per cent at m=10^11.5^M_{sun}_, with differences of up to 1dex between the different spectral models used to estimate the SFH and on how we treat aperture effects. But old stellar populations may hide in our VYGs despite our conservative VYG sample built with galaxies that are globally bluer than within the region viewed by the SDSS fibre. The VYG fractions versus mass decrease more gradually compared to the Tweed et al. (2018MNRAS.477.1427T) predictions using analytical and semi-analytical models of galaxy formation, but agree better with the SIMBA hydrodynamical simulation. These discrepancies highlight the usefulness of VYGs in constraining the strong uncertainties in both galaxy formation models and spectral modelling of galaxy SFHs. Given the lognormal cosmic SFH, these mean VYG fractions suggest that galaxies above 10^8^M_{sun}_ undergo at most four major starbursts on average.
- ID:
- ivo://CDS.VizieR/J/ApJS/214/18
- Title:
- VII log(gf) values, and V abundance in HD 84937
- Short Name:
- J/ApJS/214/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Two spectrometers, independent radiometric calibration methods, and independent data analysis routines enable a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log{epsilon}(V)=3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H]=-2.08 from 68 lines, leading to a value of [V/Fe]=0.24.
- ID:
- ivo://lam.cesam.aspic/vipers_dr2/q/ssa
- Title:
- VIPERS PDR-2 - Simple Spectrum Access
- Short Name:
- VIPERS2 SSAP
- Date:
- 24 Aug 2021 14:22:40
- Publisher:
- The CeSAM VO team
- Description:
- Spectra from the second data release (PDR-2) of VIPERS.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A9
- Title:
- VIPGI spectroscopic templates for FORS2
- Short Name:
- J/A+A/550/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The goal of this paper is twofold. Firstly, we present F-VIPGI, a new version of the VIMOS Interactive Pipeline and Graphical Interface (VIPGI) adapted to handle FORS2 spectroscopic data taken with the standard instrument configuration. Secondly, we investigate the spectro-photometric properties of a sample of galaxies residing in distant X-ray selected galaxy clusters, the optical spectra of which were reduced with this new pipeline.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/191
- Title:
- VI photometry and spectroscopy in h+{chi} Per
- Short Name:
- J/ApJS/186/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From photometric observations of ~47000 stars and spectroscopy of ~11000 stars, we describe the first extensive study of the stellar population of the famous Double Cluster, h and {chi} Persei, down to subsolar masses. By analyzing optical spectra and optical/infrared photometry, we constrain the distance moduli (dM), reddening (E(B-V)), and ages for h Persei, {chi} Persei, and the low-density halo population surrounding both cluster cores. With the exception of mass and spatial distribution, the clusters are nearly identical in every measurable way. From these data, we establish the first spectroscopic and photometric membership lists of cluster stars down to early/mid M dwarfs. At minimum, there are ~5000 members within 10' of the cluster centers, while the entire h and {chi} Persei region has at least ~13000 and as many as 20000 members. The Double Cluster contains ~8400M_{sun}_ of stars within 10' of the cluster centers. We estimate a total mass of at least 20000M_{sun}_. We conclude our study by outlining outstanding questions regarding the past and present properties of h and {chi} Persei. From comparing recent work, we compile a list of intrinsic colors and derive a new effective temperature scale for O-M dwarfs, giants, and supergiants.
- ID:
- ivo://padc.obspm.planeto/vir_ros/q/epn_core
- Title:
- VIRTIS Rosetta cometary phase (demo)
- Short Name:
- VRos
- Date:
- 28 Feb 2025 14:52:04
- Publisher:
- Paris Astronomical Data Centre - LESIA
- Description:
- Spectroscopy of comet 67P
- ID:
- ivo://CDS.VizieR/J/ApJ/704/842
- Title:
- VIRUS-P spectroscopy of NGC 5194
- Short Name:
- J/ApJ/704/842
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relation between the star formation rate (SFR) surface density ({Sigma}_SFR_) and the mass surface density of gas ({Sigma}_gas_) in NGC 5194 (a.k.a. M51a, Whirlpool Galaxy). Visible Integral field Replicable Unit Spectrograph Prototype (VIRUS-P) integral field spectroscopy of the central 4.1x4.1kpc^2^ of the galaxy is used to measure H{alpha}, H{beta}, [OIII]5007, [NII]6548,6584, and [SII]6717,6731 emission line fluxes for 735 regions ~170pc in diameter. We use the Balmer decrement to calculate nebular dust extinctions, and correct the observed fluxes in order to accurately measure {Sigma}_SFR_ in each region. Archival HI 21cm and CO maps with spatial resolution similar to that of VIRUS-P are used to measure the atomic and molecular gas surface density for each region.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A70
- Title:
- VIS3COS. III. Galaxy spectra
- Short Name:
- J/A+A/633/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic observations of 466 galaxies in and around a superstructure at z~0.84 targeted by the VIMOS Spectroscopic Survey of a Supercluster in the COSMOS eld (VIS3COS). We use [OII]3727, H{delta}, and Dn4000 to trace recent, medium-, and long-term star formation histories and investigate the eect of stellar mass and local environment on them. By studying trends in individual and composite galaxy spectra, we find that stellar mass and environment play a role in the observed galactic properties. Galaxies with low stellar mass (10<log10(M*/M_{sun}_)<10.5) in the eld show the strongest H{delta} absorption. Similarly, the massive population (log10(M*/M_{sun}_) > 11) shows an increase in H absorption strengths in intermediate-density environments (e.g. filaments). Galaxies with intermediate stellar mass (10.5<log10(M*/M_{sun}_)<11) have similar H{delta} absorption proles in all environments, but show an indication of enhanced [OII] emission in intermediate-density environments. This indicates that field galaxies with low stellar mass and lament galaxies with high stellar mass are more likely to have experienced a recent burst of star formation, while galaxies of the intermediate stellar-mass show an increase of star formation at lament-like densities. We also find that the median [OII] equivalent width (|EW[OII]|) decreases from 27+/-2{AA} to 2.0^+0,5^_-0.4_{AA} and Dn4000 increases from 1.09+/-0.01 to 1.56+/-0.03 with increasing stellar mass (from ~10^9.25^ to ~10^11.35^M_{sun}_). For the dependence on the environment, we find that at fixed stellar mass, |EW[OII]| is tentatively lower in environments with higher density. We find for Dn4000 that the increase with stellar mass is sharper in denser environments, which indicates that these environments may accelerate galaxy evolution. Moreover, we find higher Dn4000 values in denser environments at fixed stellar mass, suggesting that galaxies are on average older and/or more metal rich in these dense environments. This set of tracers depicts a scenario where the most massive galaxies have, on average, the lowest specic star formation rates and the oldest stellar populations (age>~1Gyr, showing a mass-downsizing eect). We also hypothesize that the observed increase in star formation (higher EW[OII], higher specic star formation rate) at intermediate densities may lead to quenching because we find that the quenched fraction increases sharply from the lament to cluster-like regions at similar stellar masses.
