- ID:
- ivo://CDS.VizieR/J/ApJ/748/93
- Title:
- K-band spectra for 133 nearby M dwarfs
- Short Name:
- J/ApJ/748/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present K-band spectra for 133 nearby (d < 33 pc) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H_2_O opacity (the H_2_O-K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H_2_O-K2 index as an indicator of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na I, Ca I, and H_2_O-K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and H{alpha} emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H_2_O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/510/A19
- Title:
- K-band spectra of 6 LMC globular clusters
- Short Name:
- J/A+A/510/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project whose aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for future ones. Our pilot study presents spatially integrated K-band spectra of three old (>=10Gyr) and metal poor ([Fe/H]~-1.4), and three intermediate age (1-2Gyr) and more metal rich ([Fe/H]~-0.4) globular clusters in the LMC.
- ID:
- ivo://CDS.VizieR/J/AJ/121/97
- Title:
- K-band spectroscopy of ULIRGs
- Short Name:
- J/AJ/121/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared spectroscopy for a complete sample of 33 ultraluminous infrared galaxies at a resolution of R~1000. Most of the wavelength range from 1.80-2.20{mu}m in the rest frame is covered, including the Pa{alpha} and Br{gamma} hydrogen recombination lines, and the molecular hydrogen vibration-rotation 1-0 S(1) and S(3) lines. Other species, such as He I, [Fe II], and [Si VI] appear in the spectra as well, in addition to a number of weaker molecular hydrogen lines. Nuclear extractions for each of the individual galaxies are presented here, along with spectra of secondary nuclei, where available. The Pa{alpha} emission is seen to be highly concentrated on the nuclei, typically with very little emission extending beyond a radius of 1kpc. This survey was carried out primarily to search for signatures of active nuclei via velocity-broadened hydrogen recombination or the presence of the [Si VI] coronal line. These signatures are rare in the present sample, occurring in only two of the 33 galaxies. The extinction to the hydrogen recombination lines is investigated via the Pa{alpha}/Br{gamma} line ratio. It is found that visual extinctions to the nuclei in excess of 10mag are relatively common among ULIRGs and that visual extinctions greater than 25mag are necessary to conceal a QSO emitting half the total bolometric luminosity. The ionized hydrogen regions in many ULIRGs are sufficiently obscured that dust-enshrouded active galactic nuclei would remain hidden at 2{mu}m at the current level of sensitivity. The vibration-rotation lines of molecular hydrogen appear to be predominantly thermal in origin, with effective temperatures generally around 2200K. The relative nuclear velocities between double nucleus ULIRGs are investigated, through which it is inferred that the maximum deprojected velocity difference is ~200km.s-1. This figure is lower than the velocities predicted by physical models of strong interactions/mergers of large, gas-rich galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A110
- Title:
- K band spectrum of beta Pictoris b
- Short Name:
- J/A+A/633/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Beta Pictoris is arguably one of the most studied stellar systems outside of our own. Some 30 years of observations have revealed a highly-structured circumstellar disk, with rings, belts, and a giant planet: beta Pictoris b. However very little is known about how this system came into being. Our objective is to estimate the C/O ratio in the atmosphere of {beta} Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry. We used the GRAVITY instrument with the four 8.2m telescopes of the Very Large Telescope Interferometer to obtain K-band spectro-interferometric data on {beta} Pic b. We extracted a medium resolution (R=500) K-band spectrum of the planet and a high- precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio. Our new astrometry disfavors a circular orbit for beta Pic b (e=0.15^+0.05^_-0.04_). Combined with previous results and with Hipparcos/GAIA measurements, this astrometry points to a planet mass of M=12.7+/-2.2M_{Jup}_. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of beta Pic b. In particular, the C/O ratios derived with the two codes are identical (0.43+/-0.05 vs $0.43^+0.04^_-0.03_). We argue that if the stellar C/O in beta Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment.
- ID:
- ivo://CDS.VizieR/J/ApJS/173/471
- Title:
- Keck DEIMOS spectroscopy of GALEX sources
- Short Name:
- J/ApJS/173/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a pilot program to obtain spectroscopy for objects detected in the Galaxy Evolution Explorer (GALEX) Medium Imaging Survey (MIS). Our study examines the properties of galaxies detected by GALEX fainter than the Sloan Digital Sky Survey (SDSS) spectroscopic survey. This is the first study to extend the techniques of Salim and coworkers to estimate stellar masses, star formation rates (SFRs), and the b (star formation history) parameter for star-forming galaxies out to z~0.7. We obtain redshifts for 50 GALEX MIS sources reaching NUV=23.9 (AB mag) having counterparts in the SDSS Data Release 4 (DR4). Of our sample, 43 are star-forming galaxies with z<0.7, 3 have emission-line ratios indicative of active galactic nuclei with z<0.7, and 4 objects with z>1 are QSOs, 3 of which are not previously cataloged. We compare our sample to a much larger sample of ~50000 matched GALEX/SDSS galaxies with SDSS spectroscopy; while our survey is shallow, the optical counterparts to our sources reach ~3mag fainter in SDSS r than the SDSS spectroscopic sample. We use emission-line diagnostics for the galaxies to determine that the sample contains mostly star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/721/1
- Title:
- Keck ESI observations of Ly{alpha} systems
- Short Name:
- J/ApJ/721/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a survey of SDSS quasars selected for strong HI damped Ly{alpha} (DLA) absorption with corresponding low equivalent width absorption from strong low-ion transitions (e.g., CII{lambda}1334 and SiII{lambda}1260). These metal-poor DLA candidates were selected from the SDSS fifth release quasar spectroscopic database, and comprise a large new sample for probing low-metallicity galaxies. Medium-resolution echellette spectra from the Keck Echellette Spectrograph and Imager spectrograph for an initial sample of 35 systems were obtained to explore the metal-poor tail of the DLA distribution and to investigate the nucleosynthetic patterns at these metallicities. We have estimated saturation corrections for the moderately underresolved spectra, and systems with very narrow Doppler parameters (b<=5km/s) will likely have underestimated abundances. For those systems with Doppler parameters b>5km/s, we have measured low-metallicity DLA gas with [X/H]<-2.4 for at least one of C, O, Si, or Fe. Assuming non-saturated components, we estimate that several DLA systems have [X/H]<-2.8, including five DLA systems with both low equivalent widths and low metallicity in transitions of both CII and OI. All of the measured DLA metallicities, however, exceed or are consistent with a metallicity of at least 1/1000 of solar, regardless of the effects of saturation in our spectra.
- ID:
- ivo://CDS.VizieR/III/211
- Title:
- Keck/HIRES Sky Line Atlas
- Short Name:
- III/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog provides a list of atmospheric OH and O2 lines that are useful for wavelength calibration of high resolution spectra. Tables of observed OH lines, and calculated wavelengths for molecular oxygen (O2) are given; the journal of the observations is found in the "Tables 1" section below, and spectra with identified lines are provided as postscript figures, which are summarized in the "figs.dat" file.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A17
- Title:
- Keck+HIRES spectra of HD 80606 and HD 80607
- Short Name:
- J/A+A/582/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the probable chemical signature of planet formation in the remarkable binary system HD 80606/7. The star HD 80606 hosts a giant planet with 4 MJup detected by both transit and radial velocity techniques. We study condensation temperature Tc trends of volatile and refractory element abundances to determine whether there is a depletion of refractories that could be related to the terrestrial planet formation. Finally, we speculate about a possible planet around the star HD 80607.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/251
- Title:
- Keck/LRIS confirmation of Coma membership
- Short Name:
- J/ApJ/723/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of the lowest and highest surface brightness faint (19<R<22) dwarf galaxy candidates in the core region of the Coma Cluster. These spectra are used to measure redshifts and establish membership for these faint dwarf populations. The primary goal of the low surface brightness sample is to test our ability to use morphological and surface brightness criteria to distinguish between Coma Cluster members and background galaxies using high resolution Hubble Space Telescope/Advanced Camera for Surveys images. Candidates were rated as expected members, uncertain, or expected background. From 93 spectra, 51 dwarf galaxy members and 20 background galaxies are identified. Our morphological membership estimation success rate is ~100% for objects expected to be members and better than ~90% for galaxies expected to be in the background. We confirm that low surface brightness is a very good indicator of cluster membership. High surface brightness galaxies are almost always background with confusion arising only from the cases of the rare compact elliptical (cE) galaxies. The more problematic cases occur at intermediate surface brightness. Many of these galaxies are given uncertain membership ratings, and these were found to be members about half of the time. In a sample of 47 high surface brightness, ultracompact dwarf candidates, 19 objects have redshifts which place them in the Coma Cluster, while another 6 have questionable redshift measurements but may also prove to be members.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/123
- Title:
- Keck Lyman continuum spectroscopic survey (KLCS)
- Short Name:
- J/ApJ/869/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star-forming galaxies at z~3. We measure the ratio of ionizing to non-ionizing UV flux density <f_900_/f_1500_>_obs_, where f_900_ is the mean flux density evaluated over the range [880,910]{AA}. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of <f_900_/f_1500_>_out_, including a full-sample average <f_900_/f_1500>_out_=0.057{+/-}0.006. We show that <f_900_/f_1500_>_out_ increases monotonically with W_{lambda}_(Ly{alpha}), inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction f_c_ of the stellar continuum is covered by gas with column density N_HI_. We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L_900_/L_1500_)_int_ along with f_c_, N_HI_, E(B-V), and f_esc,abs_, the absolute escape fraction of ionizing photons. We find a sample-averaged f_esc,abs_=0.09{+/-}0.01, with subsamples falling along a linear relation <f_esc,abs_>~0.75[W_{lambda}_(Ly{alpha})/110{AA}]. Using the far-UV luminosity function, the distribution function n(W(Ly{alpha})), and the relationship between W_{lambda}_(Ly{alpha}) and <f_900_/f_1500_>_out_, we estimate the total ionizing emissivity of z~3 star-forming galaxies with M_uv_<=-19.5, which exceeds the contribution of quasi-stellar objects by a factor of ~3, and accounts for ~50% of the total {epsilon}LyC at z~3 estimated using indirect methods.
