Search

Start Over Subject galaxies
3401. Spectroscopic study of Leo V dSph
ID:
ivo://CDS.VizieR/J/ApJ/694/L144
Title:
Spectroscopic study of Leo V dSph
Short Name:
J/ApJ/694/L144
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic study of Leo V, a recently discovered satellite of the Milky Way (MW). From stellar spectra obtained with the MMT/Hectochelle spectrograph we identify seven likely members of Leo V. Five cluster near the Leo V center (R<3') and have a velocity dispersion of 2.4^+2.4^_1.4_km/s. The other two likely members lie near each other but far from the center (R~13'~700pc) and inflate the global velocity dispersion to 3.7^+2.3^_1.4_km/s.
3402. Spectroscopic study of 65 nearby galaxies
ID:
ivo://CDS.VizieR/J/A+A/519/A40
Title:
Spectroscopic study of 65 nearby galaxies
Short Name:
J/A+A/519/A40
Date:
21 Oct 2021
Publisher:
CDS
Description:
With the aim of constraining the source of excitation and the origin of the ionized gas in early-type galaxies (ETGs), we analyzed intermediate resolution optical spectra of a sample of 65 ETGs mostly located in low density environments. Optical emission lines are detected in 89% of the sample. The incidence and strength of emission do not correlate either with the E/S0 classification, or with the fast/slow rotator classification. Comparing the nuclear r<r_e_/16 line emission with the classical [OIII]/Hb vs [NII]/Ha diagnostic diagram, the galaxy activity is so classified: 72% of the galaxies with emission are LINERs, 9% are Seyferts, 12% are Composite/Transition objects, and 7% are non-classified. Seyferts have young luminosity-weighted ages (<5Gyr), and appear, on average, significantly younger than LINERs and Composites. Excluding the Seyferts from our sample, we find that the spread in the ([OIII], Ha or [NII]) emission strength increases with the galaxy central velocity dispersion sigma_c_. The [NII]/Ha ratio decreases with increasing galacto-centric distance, indicating either a decrease of the nebular metallicity, or a progressive "softening" of the ionizing spectrum. The average oxygen abundance of the ionized gas is slightly less than solar, and a comparison with the results obtained in Paper III (Cat. J/A+A/463/455) from Lick indices reveals that it is ~0.2dex lower than that of stars. Conclusions: the nuclear emission can be explained with photoionization by PAGB stars alone only in ~22% of the LINERs/Composite sample. On the other hand, we can not exclude an important role of PAGB star photoionization at larger radii. For the major fraction of the sample, the nuclear emission is consistent with excitation from a low-accretion rate AGN, fast shocks (200-500km/s) in a relatively gas-poor environment (n<100cm^-3^), or coexistence of the two. The derived nebular metallicities suggest either an external origin of the gas, or an overestimate of the oxygen yields by SN models.
3403. Spectroscopic study of Segue 2
ID:
ivo://CDS.VizieR/J/MNRAS/397/1748
Title:
Spectroscopic study of Segue 2
Short Name:
J/MNRAS/397/1748
Date:
21 Oct 2021
Publisher:
CDS
Description:
We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope (MMT). From this, we derive a luminosity of Mv=-2.5, a half-light radius of 34pc and a systemic velocity of ~-40km/s. Our data also provide evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighbouring fields. We resolve the velocity dispersion of Segue 2 as 3.4km/s and the possible stream as ~7km/s. This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites - survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts z>10 and are good candidates for fossils of the reionization epoch.
3404. Spectroscopic survey of hypervelocity stars
ID:
ivo://CDS.VizieR/J/ApJ/647/303
Title:
Spectroscopic survey of hypervelocity stars
Short Name:
J/ApJ/647/303
Date:
21 Oct 2021
Publisher:
CDS
Description:
We discuss our targeted search for hypervelocity stars (HVSs), stars traveling with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Our survey, now half-complete, has successfully identified a total of four probable HVSs plus a number of other unusual objects. Here we report the two most recently discovered HVSs: SDSS J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with Galactic rest-frame velocities at least +508+/-12 and 418+/-10km/s, respectively.
3405. Spectroscopic survey of WISE-selected sources
ID:
ivo://CDS.VizieR/J/AJ/143/7
Title:
Spectroscopic survey of WISE-selected sources
Short Name:
J/AJ/143/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the results of an optical spectroscopic survey at high Galactic latitude (|b|>=30{deg}) of a sample of WISE-selected targets, grouped by WISE W1 ({lambda}_eff_=3.4{mu}m) flux, which we use to characterize the sources WISE detected. We observed 762 targets in 10 disjoint fields centered on ultraluminous infrared galaxy candidates using DEIMOS on Keck II. We find 0.30+/-0.02 galaxies arcmin^-2^ with a median redshift of z=0.33+/-0.01 for the sample with W1>=120{mu}Jy. The foreground stellar densities in our survey range from 0.23+/-0.07arcmin^-2^ to 1.1+/-0.1arcmin^-2^ for the same sample. We obtained spectra that produced science grade redshifts for >=90% of our targets for sources with W1 flux >=120{mu}Jy that also had an i-band flux >=18{mu}Jy. We used this for targeting very preliminary data reductions available to the team in 2010 August. Our results therefore present a conservative estimate of what is possible to achieve using WISE's Preliminary Data Release for the study of field galaxies.
3406. Spectroscopy and abundances of SINGS galaxies
ID:
ivo://CDS.VizieR/J/ApJS/190/233
Title:
Spectroscopy and abundances of SINGS galaxies
Short Name:
J/ApJS/190/233
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present intermediate-resolution optical spectrophotometry of 65 galaxies obtained in support of the Spitzer Infrared Nearby Galaxies Survey (SINGS). For each galaxy we obtain a nuclear, circumnuclear, and semi-integrated optical spectrum designed to coincide spatially with mid- and far-infrared spectroscopy from the Spitzer Space Telescope. We make the reduced, spectrophotometrically calibrated one-dimensional spectra, as well as measurements of the fluxes and equivalent widths of the strong nebular emission lines, publically available. We use optical emission-line ratios measured on all three spatial scales to classify the sample into star-forming, active galactic nuclei (AGNs), and galaxies with a mixture of star formation and nuclear activity. We find that the relative fraction of the sample classified as star forming versus AGN is a strong function of the integrated light enclosed by the spectroscopic aperture. We supplement our observations with a large database of nebular emission-line measurements of individual HII regions in the SINGS galaxies culled from the literature. We use these ancillary data to conduct a detailed analysis of the radial abundance gradients and average HII-region abundances of a large fraction of the sample. We combine these results with our new integrated spectra to estimate the central and characteristic (globally averaged) gas-phase oxygen abundances of all 75 SINGS galaxies. We conclude with an in-depth discussion of the absolute uncertainty in the nebular oxygen abundance scale.
3407. Spectroscopy and photometry of z~=5 galaxies
ID:
ivo://CDS.VizieR/J/ApJ/659/84
Title:
Spectroscopy and photometry of z~=5 galaxies
Short Name:
J/ApJ/659/84
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically selected galaxies with z'_850LP_<26.5 in the southern GOODS field. Following recent procedures introduced by Eyles et al. (2007MNRAS.374..910E), we estimate stellar masses for various subsamples for which reliable and unconfused Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most luminous sources with z{bar}=4.92 provides a firm lower limit to the stellar mass density of 1x10^6^M_{sun}_/Mpc^3^. We then consider a larger sample whose photometric redshifts in the publicly available GOODS-MUSIC catalog lie in the range 4.4<z<5.6.
3408. Spectroscopy & HST photometry of galaxy Leo V
ID:
ivo://CDS.VizieR/J/ApJ/885/53
Title:
Spectroscopy & HST photometry of galaxy Leo V
Short Name:
J/ApJ/885/53
Date:
16 Mar 2022 09:00:29
Publisher:
CDS
Description:
The ultra-faint dwarf galaxy Leo V has shown both photometric overdensities and kinematic members at large radii, along with a tentative kinematic gradient, suggesting that it may have undergone a close encounter with the Milky Way. We investigate these signs of disruption through a combination of (I) high precision photometry obtained with the Hubble Space Telescope (HST), (II) two epochs of stellar spectra obtained with the Hectochelle Spectrograph on the MMT, and (III) measurements from the Gaia mission. Using the HST data, we examine one of the reported stream-like overdensities at large radii, and conclude that it is not a true stellar stream, but instead a clump of foreground stars and background galaxies. Our spectroscopic analysis shows that one known member star is likely a binary, and challenges the membership status of three others, including two distant candidates that had formerly provided evidence for overall stellar mass loss. We also find evidence that the proposed kinematic gradient across Leo V might be due to small number statistics. We update the systemic proper motion of Leo V, finding ({mu}_{alpha}_/cos{delta},{mu}_{delta}_)= (0.009{+/-}0.560,-0.777{+/-}0 .314)mas/yr, which is consistent with its reported orbit that did not put Leo V at risk of being disturbed by the Milky Way. These findings remove most of the observational clues that suggested Leo V was disrupting; however, we also find new plausible member stars, two of which are located >5 half-light radii from the main body. These stars require further investigation. Therefore, the nature of Leo V still remains an open question.
3409. Spectroscopy in Abell 3921
ID:
ivo://CDS.VizieR/J/A+A/557/A62
Title:
Spectroscopy in Abell 3921
Short Name:
J/A+A/557/A62
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectrophotometric analysis of the galaxy population in the area of the merging cluster Abell 3921 at z=0.093. We investigate the impact of the complex cluster environment on galaxy properties such as morphology or star formation rate. We combine multi-object spectroscopy from the Two Degree Field (2dF) spectrograph with optical imaging taken with the ESO Wide Field Imager. We carry out a redshift analysis and determine cluster velocity dispersions using biweight statistics. Applying a Dressler-Shectman test we seek evidence for cluster substructure. Cluster and field galaxies are investigated with respect to [OII] and H{alpha} equivalent width, star formation rate and morphological descriptors such as concentration index and Gini coefficient. We study these cluster galaxy properties as a function of clustercentric distance and investigate the spatial distribution of various galaxy types. Applying the Dressler-Shectman test we find a third component (A3921-C) in addition to the two main subclusters (A3921-A and A3921-B) already known. The re-determined mass ratio between the main components A and B is ~2:1. Similar to previous studies of galaxy clusters, we find that a large fraction of the disk galaxies close to the cluster core show no detectable star formation. These are likely systems that are quenched due to ram pressure stripping. Interestingly, we also find quenched spirals at rather large distances of 3-4Mpc from the cluster core.
3410. Spectroscopy in cluster RDCS J1252.9-2927 (z=1.2)
ID:
ivo://CDS.VizieR/J/A+A/507/671
Title:
Spectroscopy in cluster RDCS J1252.9-2927 (z=1.2)
Short Name:
J/A+A/507/671
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent wide-field imaging observations of the X-ray luminous cluster RDCS J1252.9-2927 at z=1.24 uncovered several galaxy groups that appear to be embedded in filamentary structure extending from the cluster core. We make a spectroscopic study of the galaxies in these groups using GMOS on Gemini-South and FORS2 on VLT with the aim of determining if these galaxies are physically associated to the cluster. We find that three groups contain galaxies at the cluster redshift and that they are probably bound to the cluster. This is the first confirmation of filamentary structure as traced by galaxy groups at z>1. We then use several spectral features in the FORS2 spectra to determine the star formation histories of group galaxies.

Limit your search

more »

more »

more »

more »

  • 24,327
  • 11