- ID:
- ivo://CDS.VizieR/J/ApJ/870/122
- Title:
- Spectroscopy of low-metallicity star candidates
- Short Name:
- J/ApJ/870/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an observing campaign to identify low-metallicity stars in the Best & Brightest Survey. From medium-resolution (R~1200-2000) spectroscopy of 857 candidates, we estimate the stellar atmospheric parameters (T_eff_, logg, and [Fe/H]), as well as carbon and {alpha}-element abundances. We find that 69% of the observed stars have [Fe/H]<=-1.0, 39% have [Fe/H]<=-2.0, and 2% have [Fe/H]<=-3.0. There are also 133 carbon-enhanced metal-poor (CEMP) stars in this sample, with 97 CEMP Group I and 36 CEMP Group II stars identified in the A(C) versus [Fe/H] diagram. A subset of the confirmed low-metallicity stars were followed-up with high-resolution spectroscopy, as part of the R-process Alliance, with the goal of identifying new highly and moderately r-process-enhanced stars. Comparison between the stellar atmospheric parameters estimated in this work and from high-resolution spectroscopy exhibit good agreement, confirming our expectation that medium-resolution observing campaigns are an effective way of selecting interesting stars for further, more targeted, efforts.
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- ID:
- ivo://CDS.VizieR/J/ApJ/817/87
- Title:
- Spectroscopy of luminous compact blue galaxies
- Short Name:
- J/ApJ/817/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M>10^15^M_{sun}_), intermediate redshift (0.5<z<0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size-luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs at the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/139/2620
- Title:
- Spectroscopy of M81 globular clusters
- Short Name:
- J/AJ/139/2620
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained spectra of 74 globular clusters (GCs) in M81. These GCs had been identified as candidates in a Hubble Space Telescope (HST) Advanced Camera for Surveys I-band survey. Sixty-eight of these 74 clusters lie within 7' of the M81 nucleus. Sixty-two of these clusters are newly spectroscopically confirmed, more than doubling the number of confirmed M81 GCs from 46 to 108. We determined metallicities for our 74 observed clusters using an empirical calibration based on Milky Way GCs.
- ID:
- ivo://CDS.VizieR/J/AJ/147/20
- Title:
- Spectroscopy of 447 nearby M dwarfs
- Short Name:
- J/AJ/147/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present metallicities, radial velocities, and near-infrared (NIR) spectral types for 447 M dwarfs determined from moderate resolution (R{approx}2000) NIR spectra obtained with the NASA Infrared Telescope Facility (IRTF)/SpeX. These M dwarfs are primarily targets of the MEarth Survey, a transiting planet survey searching for super Earths around mid-to-late M dwarfs within 33pc. We present NIR spectral types for each star and new spectral templates for the IRTF in the Y, J, H, and K-bands, created using M dwarfs with near-solar metallicities. We developed two spectroscopic distance calibrations that use NIR spectral type or an index based on the curvature of the K-band continuum. Our distance calibration has a scatter of 14%. We searched 27 NIR spectral lines and 10 spectral indices for metallicity sensitive features, taking into account correlated noise in our estimates of the errors on these parameters. We calibrated our relation using 36 M dwarfs in common proper pairs with an F-, G-, or K-type star of known metallicity. We validated the physical association of these pairs using proper motions, radial velocities, and spectroscopic distance estimates. Our resulting metallicity calibration uses the sodium doublet at 2.2{mu}m as the sole indicator for metallicity. It has an accuracy of 0.12dex inferred from the scatter between the metallicities of the primaries and the estimated metallicities of the secondaries. Our relation is valid for NIR spectral types from M1V to M5V and for -1.0dex<[Fe/H]<+0.35dex. We present a new color-color metallicity relation using J-H and J-K colors that directly relates two observables: the distance from the M dwarf main sequence and equivalent width of the sodium line at 2.2{mu}m. We used radial velocities of M dwarf binaries, observations at different epochs, and comparison between our measurements and precisely measured radial velocities to demonstrate a 4km/s accuracy.
- ID:
- ivo://CDS.VizieR/J/AJ/143/126
- Title:
- Spectroscopy of 462 nearby Type Ia supernovae
- Short Name:
- J/AJ/143/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 2603 spectra of 462 nearby Type Ia supernovae (SNe Ia), including 2065 previously unpublished spectra, obtained during 1993-2008 through the Center for Astrophysics Supernova Program. There are on average eight spectra for each of the 313 SNe Ia with at least two spectra. Most of the spectra were obtained with the FAST spectrograph at the Fred Lawrence Whipple Observatory 1.5m telescope and reduced in a consistent manner, making this data set well suited for studies of SN Ia spectroscopic diversity. Using additional data from the literature, we study the spectroscopic and photometric properties of SNe Ia as a function of spectroscopic class using the classification schemes of Branch et al. (2006PASP..118..560B) and Wang et al. (2009, Cat. J/ApJ/699/L139). The width-luminosity relation appears to be steeper for SNe Ia with broader lines, although the result is not statistically significant with the present sample. Based on the evolution of the characteristic SiII{lambda}6355 line, we propose improved methods for measuring velocity gradients, revealing a larger range than previously suspected, from ~0 to ~400km/s/day considering the instantaneous velocity decline rate at maximum light.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/2265
- Title:
- Spectroscopy of NGC3310 HII regions
- Short Name:
- J/MNRAS/440/2265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Numerical simulations of minor mergers predict little enhancement in the global star formation activity. However, it is still unclear the impact they have on the chemical state of the whole galaxy and on the mass build-up in the galaxy bulge and disc. We present a two-dimensional analysis of NCG 3310, currently undergoing an intense starburst likely caused by a recent minor interaction, using data from the PPAK Integral Field Spectroscopy Nearby Galaxies Survey (PINGS). With data from a large sample of about a hundred HII regions identified throughout the disc and spiral arms, we derive, using strong-line metallicity indicators and direct derivations, a rather flat gaseous abundance gradient. Thus, metal mixing processes occurred, as in observed galaxy interactions. Spectra from PINGS data and additional multiwavelength imaging were used to perform a spectral energy distribution fitting to the stellar emission and a photoionization modelling of the nebulae. The ionizing stellar population is characterized by single populations with a narrow age range (2.5-5Myr) and a broad range of masses (10^4^-6x10^6^M_{sun}_). The effect of dust grains in the nebulae is important, indicating that 25-70% of the ultraviolet photons can be absorbed by dust. The ionizing stellar population within the Hii regions represents typically a few per cent of the total stellar mass. This ratio, a proxy to the specific star formation rate, presents a flat or negative radial gradient. Therefore, minor interactions may indeed play an important role in the mass build-up of the bulge.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2828
- Title:
- Spectroscopy of northern NLTT stars
- Short Name:
- J/AJ/123/2828
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present initial results of an all-sky search for late-type dwarfs within 20pc of the Sun using the New Luyten Two-Tenths (NLTT) catalog cross-referenced with the Two Micron All Sky Survey (2MASS) database. The results were obtained with low-resolution optical spectroscopic follow-up of candidate nearby stars as a preliminary test of our methodology. M_J_, derived using spectral indices, and 2MASS J are used to estimate distances. Out of the 70 objects observed, 28 are identified as previously unrecognized objects within 25pc of the Sun, and up to 19 of these are within 20pc. One, LP 647-13, is an M9-type dwarf at 10.5pc, making it one of the four closest M9 dwarfs currently known. We also discuss the chromospheric activity of the observed dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJS/175/29
- Title:
- Spectroscopy of QSO pairs
- Short Name:
- J/ApJS/175/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ly{alpha} forest has opened a new redshift regime for cosmological investigation. At z>2 it provides a unique probe of cosmic geometry and an independent constraint on dark energy that is not subject to standard candle or ruler assumptions. In Paper I of this series on using the Ly{alpha} forest observed in pairs of QSOs for a new application of the Alcock-Paczynski test, we present and discuss the results of a campaign to obtain moderate-resolution spectroscopy (FWHM~2.5{AA}) of the Ly{alpha} forest in pairs of QSOs with small redshift differences ({Delta}z<0.25, z>2.2) and arcminute separations ({Theta}<5'). This data set, composed of seven individual QSOs, 35 pairs, and one triplet, is also well suited for future investigations of the coherence of Ly{alpha} absorbers on ~1Mpc transverse scales and the transverse proximity effect. We note seven revisions for previously published QSO identifications and/or redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/17
- Title:
- Spectroscopy of quiescent gal. in 9 lensing clusters
- Short Name:
- J/ApJ/902/17
- Date:
- 03 Mar 2022 11:35:20
- Publisher:
- CDS
- Description:
- We measure the central stellar velocity dispersion function for quiescent galaxies in a set of nine northern clusters in the redshift range 0.18<z<0.29 and with strong lensing arcs in Hubble Space Telescope images. The velocity dispersion function links galaxies directly to their dark matter halos. From dense SDSS and MMT/Hectospec spectroscopy, we identify 222-463 spectroscopic members in each cluster. We derive physical properties of cluster members including redshift, D_n_4000, and central stellar velocity dispersion and we include a table of these measurements for 3419 cluster members. We construct the velocity dispersion functions for quiescent galaxies with D_n_4000>1.5 and within R200. The cluster velocity dispersion functions all show excesses at {sigma}>~250km/s compared to the field velocity dispersion function. The velocity dispersion function slope at large velocity dispersion ({sigma}>160km/s) is steeper for more massive clusters, consistent with the trend observed for cluster luminosity functions. The spatial distribution of galaxies with large velocity dispersion at radii larger than R200 further underscores the probable major role of dry mergers in the growth of massive cluster galaxies during cluster assembly.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A57
- Title:
- Spectroscopy of 400 red giants in the Bulge
- Short Name:
- J/A+A/546/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence of two stellar populations in the Milky Way bulge has been reported recently, based on observations of giant and dwarf stars in the inner an intermediate bulge. We aim at studying the abundances and kinematics of stars in the outer Galactic bulge, thereby providing additional constraints on formation models of the bulge. Spectra of 401 red giant stars in a field at (l,b)=(0,-10) were obtained with the FLAMES-GIRAFFE spectrograph at the VLT. Stars of luminosities down to below the two bulge red clumps are included in the data set. From these spectra we measure general metallicities, abundances of iron and the alpha-elements, and radial velocities of the stars. The abundances are derived from an interpolation and fitting procedure within a grid of COMARCS model atmospheres and spectra. These measurements as well as photometric data are compared to simulations with the Besancon and TRILEGAL models of the Galaxy. We confirm the presence of two populations among our sample stars: i) a metal-rich one at [M/H]~+0.3, comprising about 30% of the sample, with low velocity dispersion and low alpha-abundance, and ii) a metal-poor population at [M/H]~-0.6 with high velocity dispersion and high alpha-abundance. The metallicity difference between the two populations, a systematically and statistically robust figure, is Delta[M/H]=0.87+-0.03. The metal-rich population could be connected to the Galactic bar. We identify this population as the carrier of the double red clump feature. We do not find a significant difference in metallicity or radial velocity between the two red clumps, a small difference in metallicity being probably due to a selection effect and contamination by the metal-poor population. The velocity dispersion agrees well with predictions of the Besancon Galaxy model, but the metallicity of the "thick bulge" model component should be shifted to lower metallicity by 0.2 to 0.3dex to well reproduce the observations. We present evidence that the metallicity distribution function depends on the evolutionary state of the sample stars, suggesting that enhanced mass loss preferentially removes metal-rich stars. We also confirm the decrease of alpha-element over-abundance with increasing metallicity. Conclusions: Our sample is consistent with the existence of two populations, one being a metal-rich bar, the second one being more like a metal-poor classical bulge with larger velocity dispersion.
