- ID:
- ivo://CDS.VizieR/J/A+A/622/A110
- Title:
- Spectroscopic membership for NGC 3532
- Short Name:
- J/A+A/622/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the 3.9m Anglo-Australian Telescope and 391 stars for observations with the Hydra-South spectrograph at the 4m Victor Blanco Telescope, obtaining spectroscopic observations over a decade for 145 stars. We measured radial velocities for our targets through cross-correlation with model spectra and standard stars, and supplemented them with radial velocities for 433 additional stars from the literature. We also measured logg, Teff, and [Fe/H] from the AAOmega spectra. The radial velocity distribution emerging from the observations is centred at 5.43+/-0.04km/s and has a width (standard deviation) of 1.46km/s. Together with proper motions from Gaia DR2 we find 660 exclusive members, of which five are likely binary members. The members are distributed across the whole cluster sequence, from giant stars to M dwarfs, making NGC~3532 one of the richest Galactic open clusters known to date, on par with the Pleiades. From further spectroscopic analysis of 153 dwarf members we find the metallicity to be marginally sub-solar, with [Fe/H]=-0.07+/-0.10. We confirm the extremely low reddening of the cluster, E_B-V_=0.034+/-0.012mag, despite its location near the Galactic plane. Exploiting trigonometric parallax measurements from Gaia DR2 we find a distance of 484^+35^_-30_pc [(m-M)_0_=8.42+/-0.14mag]. Based on the membership we provide an empirical cluster sequence in multiple photometric passbands. A comparison of the photometry of the measured cluster members with several recent model isochrones enables us to confirm the 300Myr cluster age. However, all of the models evince departures from the cluster sequence in particular regions, especially in the lower mass range.
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- ID:
- ivo://CDS.VizieR/J/ApJ/770/16
- Title:
- Spectroscopic members of Segue 2 galaxy
- Short Name:
- J/ApJ/770/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Segue 2, discovered by Belokurov et al. (2009, Cat. J/MNRAS/397/1748), is a galaxy with a luminosity of only 900L_{sun}_. We present Keck/DEIMOS spectroscopy of 25 members of Segue 2 - a threefold increase in spectroscopic sample size. The velocity dispersion is too small to be measured with our data. The upper limit with 90% (95%) confidence is {sigma}_v_<2.2(2.6)km/s, the most stringent limit for any galaxy. The corresponding limit on the mass within the three-dimensional half-light radius (46pc) is M_1/2_<1.5(2.1)x10^5^M_{sun}_. Segue 2 is the least massive galaxy known. We identify Segue 2 as a galaxy rather than a star cluster based on the wide dispersion in [Fe/H] (from -2.85 to -1.33) among the member stars. The stars' [{alpha}/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained Type Ia supernova ejecta despite its presently small mass and that star formation lasted for at least 100 Myr. The mean metallicity, <[Fe/H]>=-2.22+/-0.13 (about the same as the Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the Milky Way. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternatively, Segue 2 could have been born in a very low mass dark matter subhalo (v_max_<10km/s), below the atomic hydrogen cooling limit.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/46
- Title:
- Spectroscopic observations in VV124 (UGC 4879)
- Short Name:
- J/ApJ/751/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial velocities for different components of the galaxy, and photometry hinted at the presence of a stellar disk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS). We validated members based on their positions in the color-magnitude diagram, radial velocities, and spectral features. Our sample contains 67 members. The average radial velocity is <v_r_>=-29.1+/-1.3km/s in agreement with the previous radio measurements of H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by velocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an upper limit of 8.6km/s on any rotation in the photometric disk-like feature. The velocity dispersion is {sigma}_v_=9.4+/-1.0km/s, from which we inferred a mass of M_1/2_=(2.1 +/-0.2)x10^7^M_{sun}_ and a mass-to-light ratio of (M/L_V_)_1/2_=5.2+/-1.1M_{sun}_/L_{sun}_, both measured within the half-light radius. Thus, VV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines. The average metallicity, <[Fe/H]>=-1.14+/-0.06, is consistent with the mass-metallicity relation defined by dSph galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/839
- Title:
- Spectroscopic observations of globular clusters
- Short Name:
- J/MNRAS/405/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of medium-resolution spectroscopy of 28 globular clusters (GCs) in six nearby galaxies of different luminosities and morphological types, situated in M33 (15 objects), M31 (three), IC10 (four), UGCA86 (four), Holmberg IX (one) and DDO71 (one) obtained at the Special Astrophysical Observatory 6-m telescope. Measurements of Lick absorption line indices and comparison with Simple Stellar Population models enabled us to obtain their spectroscopic ages, metallicities and {alpha}-element to Fe abundance ratios.
- ID:
- ivo://CDS.VizieR/J/ApJ/653/657
- Title:
- Spectroscopic observations of Herbig Ae/Be stars
- Short Name:
- J/ApJ/653/657
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical spectra of 45 intermediate-mass Herbig Ae/Be stars. Together with the multiepoch spectroscopic and photometric data compiled for a large sample of these stars and ages estimated for individual stars by using pre-main-sequence evolutionary tracks, we have studied the evolution of emission-line activity in them. We find that, on average, the H{alpha} emission line strength decreases with increasing stellar age in Herbig Ae/Be stars, indicating that the accretion activity gradually declines during the pre-main-sequence phase.
- ID:
- ivo://CDS.VizieR/J/PAZh/32/628
- Title:
- Spectroscopic observations of southern stars
- Short Name:
- J/PAZh/32/628
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of spectrophotometric observations of 64 southern stars in the range from 320 to 730nm are presented as quasi-monochromatic luminosities from the stars on the external board of atmosphere expressed in the absolute energy units (W/m^2^/m) with spectral interval of 2.5nm.
- ID:
- ivo://CDS.VizieR/J/AJ/156/117
- Title:
- Spectroscopic orbits for late-type stars. II.
- Short Name:
- J/AJ/156/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined spectroscopic orbital elements for 13 systems - 10 single-lined binaries and three double-lined binaries. For the three binaries with previously published spectroscopic orbits, we have computed improved or comparable elements. While two systems have relatively short periods between 10 and 19 days, the remaining systems have much longer periods ranging from 604 to 9669 days. One of the single-lined systems, HD 142640, shows both short-period and long-period velocity variations and so is triple. For three systems - HD 59380, HD 160933, and HD 161163 - we have combined our spectroscopic results with Hipparcos astrometric observations to obtain astrometric orbits. For HD 14802 we have determined a joint orbital solution from spectroscopic velocities and interferometric observations. The orbits given here will be useful in combination with future interferometric and Gaia satellite observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/102
- Title:
- Spectroscopic redshift catalog in A2142 field
- Short Name:
- J/ApJ/863/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To investigate the dynamics of the galaxy cluster A2142, we compile an extended catalog of 2239 spectroscopic redshifts of sources, including 237 newly measured redshifts, within 30 arcmin from the cluster center. With the {sigma}-plateau algorithm from the caustic method, we identify 868 members and a number of substructures in the galaxy distribution both in the outskirts, out to ~3.5Mpc from the cluster center, and in the central region. In the outskirts, one substructure overlaps a falling clump of gas previously identified in the X-ray band. These substructures suggest the presence of multiple minor mergers, which are responsible for the complex dynamics of A2142, and the absence of recent or ongoing major mergers. We show that the distribution of the galaxies in the cluster core and in several substructures is consistent with the mass distribution inferred from the weak-lensing signal. Moreover, we use spatially resolved X-ray spectroscopy to measure the redshift of different regions of the intracluster medium within ~3 arcmin from the cluster center. We find a ring of gas near the two X-ray cold fronts identified in previous analyses and measure a velocity of this ring of 810+/-330km/s larger than the cluster mean velocity. Our analysis suggests the presence of another ring surrounding the core, whose velocity is 660+/-300km/s larger than the cluster velocity. These X-ray features are not associated with any optical substructures, and support the core-sloshing scenario suggested in previous work.
- ID:
- ivo://CDS.VizieR/J/PAZh/27/381
- Title:
- Spectroscopic study of BM Ori
- Short Name:
- J/PAZh/27/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two CCD spectra of the star BM Ori were obtained with the echelle spectrograph of the 6-m telescope. Measured line equivalent widths were used to estimate atmospheric parameters of the secondary star.
- 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.
