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14271. Spectroscopy of 12 [WC] planetary nebulae
ID:
ivo://CDS.VizieR/J/A+A/538/A54
Title:
Spectroscopy of 12 [WC] planetary nebulae
Short Name:
J/A+A/538/A54
Date:
21 Oct 2021
Publisher:
CDS
Description:
Planetary nebulae (PNe) around Wolf-Rayet [WR] central stars ([WR]PNe) constitute a particular photoionized nebula class that represents about 10% of the PNe with classified central stars. We analyse deep high-resolution spectrophotometric data of 12 [WR] PNe. This sample of [WR]PNe represents the most extensive analysed so far, at such high spectral resolution. We aim to select the optimal physical conditions in the nebulae to be used in ionic abundance calculations that will be presented in a forthcoming paper.
14272. Spectroscopy of W UMa-type binary stars
ID:
ivo://CDS.VizieR/J/AJ/146/70
Title:
Spectroscopy of W UMa-type binary stars
Short Name:
J/AJ/146/70
Date:
21 Oct 2021
Publisher:
CDS
Description:
This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080{AA} and 5285{AA}. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32<(B-V)_0_<0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m_1_index of the Stromgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]_1_ are distributed within -0.65<[M/H]_1_<+0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]_1_within -0.37<[M/H]_1_<+0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial velocity data for 78 binaries of the full sample, shows that the F-type sub-sample binaries (44 stars with both velocities and metallicity determinations) have similar kinematic properties to solar-neighborhood, thin-disk dwarfs with space velocity component dispersions: {sigma}U=33km/s, {sigma}V=23km/s and {sigma}W=14km/s. FU Dra with a large spatial velocity, V_tot_=197km/s and [M/H]_1_=-0.6+/-0.2, appears to be the only thick-disk object in the F-type sub-sample. The kinematic data indicate that the F-type EW binaries are typical, thin-disk population stars with ages about 3-5.5Gyr. The F-type binaries that appear to be older than the rest tend to have systematically smaller mass ratios than most of the EW binaries of the same period.
14273. Spectroscopy of X-ray sources in ECDF-S
ID:
ivo://CDS.VizieR/J/ApJ/693/1713
Title:
Spectroscopy of X-ray sources in ECDF-S
Short Name:
J/ApJ/693/1713
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results of our optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South. A total of 339 sources were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. We measured redshifts for 186 X-ray sources, including archival data and a literature search. We find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley". The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity.
14274. Spectroscopy of 3<z<4 quiescent galaxies
ID:
ivo://CDS.VizieR/J/A+A/618/A85
Title:
Spectroscopy of 3<z<4 quiescent galaxies
Short Name:
J/A+A/618/A85
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Keck-MOSFIRE H and K spectra for a sample of 24 candidate quiescent galaxies at 3<z<4, identified from their rest-frame UVJ colors and photometric redshifts in the ZFOURGE and 3DHST surveys. With median integration times of one hour in H and five in K, we obtain spectroscopic redshifts for half of the sample, using either Balmer absorption lines or nebular emission lines. We confirm the high accuracy of the photometric redshifts for this spectroscopically-confirmed sample, with a median |Zphot-Zspec|/(1+Zspec) of 1.2%. Two galaxies turn out to be dusty H{alpha} emitters at lower redshifts (z<2.5), and these are the only two detected in the sub-mm with ALMA. High equivalent-width [OIII] emission is observed in two galaxies, contributing up to 30% of the K-band flux and mimicking the UVJ colors of an old stellar population. This implies a failure rate of only 20% for the UVJ selection at these redshifts. Lastly, Balmer absorption features are identified in four galaxies, among the brightest of the sample, confirming the absence of OB stars. We then modeled the spectra and photometry of all quiescent galaxies with a wide range of star-formation histories. We find specific star-formation rates (sSFR) lower than 0.15Gyr^-1^ (a factor of ten below the main sequence) for all but one galaxy, and lower than 0.01Gyr^-1^ for half of the sample. These values are consistent with the observed H{beta} and [OII] luminosities, and the ALMA non-detections. The implied formation histories reveal that these galaxies have quenched on average 300Myr prior to being observed, between z=3.5 and 5, and that half of their stars were formed by z~5.5 with a mean SFR~300M_{sun}_/yr. We finally compared the UVJ selection to a selection based instead on the sSFR, as measured from the photometry. We find that galaxies a factor of ten below the main sequence are 40% more numerous than UVJ-selected quiescent galaxies, implying that the UVJ selection is pure but incomplete. Current models fail at reproducing our observations, and underestimate either the number density of quiescent galaxies by more than an order of magnitude, or the duration of their quiescence by a factor two. Overall, these results confirm the existence of an unexpected population of quiescent galaxies at z>3, and offer the first insights on their formation histories.
14275. Spectroscopy of 88 z<0.7 SDSS QSOs
ID:
ivo://CDS.VizieR/J/ApJS/201/23
Title:
Spectroscopy of 88 z<0.7 SDSS QSOs
Short Name:
J/ApJS/201/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out a systematic search for subparsec supermassive black hole (BH) binaries among z<~0.7 Sloan Digital Sky Survey quasars. These are predicted by models of supermassive BH and host galaxy coevolution, therefore their census and population properties constitute an important test of these models. In our working hypothesis, one of the two BHs accretes at a much higher rate than the other and carries with it the only broad emission line region of the system, making the system analogous to a single-lined spectroscopic binary star. Accordingly, we used spectroscopic principal component analysis to search for broad H{beta} emission lines that are displaced from the quasar rest frame by |{Delta}{nu}|>~1000km/s. This method also yields candidates for rapidly recoiling BHs. Of the 88 candidates, several were previously reported in the literature. We found a correlation between the peak offset and skewness of the broad H{beta} profiles, suggesting a common physical explanation for these profiles. We carried out follow-up spectroscopic observations of 68 objects to search for changes in the peak velocities of the H{beta} lines.
14276. Spectroscopy on LMC clusters
ID:
ivo://CDS.VizieR/J/ApJ/749/124
Title:
Spectroscopy on LMC clusters
Short Name:
J/ApJ/749/124
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of an ongoing program to measure detailed chemical abundances in nearby galaxies, we use a sample of young- to intermediate-age clusters in the Large Magellanic Cloud with ages of 10Myr-2Gyr to evaluate the effect of isochrone parameters, specifically core convective overshooting, on Fe abundance results from high-resolution, integrated light spectroscopy. In this work we also obtain fiducial Fe abundances from high-resolution spectroscopy of the cluster individual member stars. We compare the Fe abundance results for the individual stars to the results from isochrones and integrated light spectroscopy to determine whether isochrones with convective overshooting should be used in our integrated light analysis of young- to intermediate-age (10Myr-3Gyr) star clusters. We find that when using the isochrones from the Teramo group, we obtain more accurate results for young- and intermediate-age clusters over the entire age range when using isochrones without convective overshooting. While convective overshooting is not the only uncertain aspect of stellar evolution, it is one of the most readily parameterized ingredients in stellar evolution models, and thus important to evaluate for the specific models used in our integrated light analysis. This work demonstrates that our method for integrated light spectroscopy of star clusters can provide unique tests for future constraints on stellar evolution models of young- and intermediate-age clusters.
14277. SPECULOOS. Ultracool dwarf transit survey
ID:
ivo://CDS.VizieR/J/A+A/645/A100
Title:
SPECULOOS. Ultracool dwarf transit survey
Short Name:
J/A+A/645/A100
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the most promising avenues for the detailed study of temperate Earth-sized exoplanets is the detection of such planets in transit in front of stars that are small and near enough to make it possible to carry out a thorough atmospheric characterisation with next-generation telescopes, such as the James Webb Space telescope (JWST) or Extremely Large Telescope (ELT). In this context, the TRAPPIST-1 planets form a unique benchmark system that has garnered the interest of a large scientific community. The SPECULOOS survey is an exoplanet transit survey targeting a volume-limited (40pc) sample of ultracool dwarf stars (of spectral type M7 and later) that is based on a network of robotic 1m telescopes especially designed for this survey. The strategy for brighter and earlier targets leverages its synergy with the ongoing TESS space-based exoplanet transit survey. We define the SPECULOOS target list as the sum of three non-overlapping sub-programmes incorporating the latest type objects (Teff<3000K). Programme1 features 365 dwarfs that are small and near enough to make it possible to detail atmospheric characterisation of an 'Earth-like' planet with the upcoming James Webb Space Telescope (JWST). Programme2 features 171 dwarfs of M5-type and later for which a significant detection of a planet similar to TRAPPIST-1b should be within reach of TESS. Programme3 features 1121 dwarfs that are later than M6-type. These programmes form the basis of our statistical census of short-period planets around ultracool dwarf stars. Our compound target list includes 1657 photometrically classified late-type dwarfs, with 260 of these targets classified, for the first time, as possible nearby ultracool dwarf stars. Our general observational strategy was to monitor each target between 100 and 200hr with our telescope network, making efficient use of the synergy with TESS for our Programme2 targets and a proportion of targets in our Programme1. Based on Monte Carlo simulations, we expect to detect up to a few dozen temperate, rocky planets. We also expect a number of them to prove amenable for atmospheric characterisation with JWST and other future giant telescopes, which will substantially improve our understanding of the planetary population of the latest-type stars.
14278. SpeX library of L-type dwarfs
ID:
ivo://CDS.VizieR/J/AJ/147/34
Title:
SpeX library of L-type dwarfs
Short Name:
J/AJ/147/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of the L dwarf WISE J174102.78-464225.5, which was discovered as part of a search for nearby L dwarfs using the Wide-field Infrared Survey Explorer (WISE). The distinct triangular peak of the H-band portion of its near-infrared spectrum and its red near-infrared colors (J-K_S_=2.35+/-0.08mag) are indicative of a young age. Via comparison to spectral standards and other red L dwarfs, we estimate a near-infrared spectral type of L7+/-2 (pec). From a comparison to spectral and low-mass evolutionary models, we determine self-consistent effective temperature, logg, age, and mass values of 1450+/-100K, 4.0+/-0.25 (cm/s2), 10-100Myr, and 4-21M_Jup_, respectively. With an estimated distance of 10-30pc, we explore the possibility that WISE J174102.78-464225.5 belongs to one of the young nearby moving groups via a kinematic analysis and we find potential membership in the {beta} Pictoris or AB Doradus associations. A trigonometric parallax measurement and a precise radial velocity can help to secure its membership in either of these groups.
14279. SpeX NIR survey of 886 nearby M dwarfs
ID:
ivo://CDS.VizieR/J/ApJS/220/16
Title:
SpeX NIR survey of 886 nearby M dwarfs
Short Name:
J/ApJS/220/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of near-infrared (NIR) spectra and associated measurements for 886 nearby M dwarfs. The spectra were obtained with the NASA-Infrared Telescope Facility SpeX Spectrograph during a two-year observing campaign; they have high signal-to-noise ratios (S/N>100-150), span 0.8-2.4{mu}m, and have R~2000. Our catalog of measured values contains useful T_eff_ and composition-sensitive features, empirical stellar parameter measurements, and kinematic, photometric, and astrometric properties compiled from the literature. We focus on measurements of M dwarf abundances ([Fe/H] and [M/H]), capitalizing on the precision of recently published empirical NIR spectroscopic calibrations. We explore systematic differences between different abundance calibrations, and from other similar M dwarf catalogs. We confirm that the M dwarf abundances we measure show the expected inverse dependence with kinematic-, activity-, and color-based age indicators. Finally, we provide updated [Fe/H] and [M/H] for 16 M dwarf planet hosts. This catalog represents the largest published compilation of NIR spectra and associated parameters for M dwarfs. It provides a rich and uniform resource for nearby M dwarfs, and will be especially valuable for measuring Habitable Zone locations and comparative abundances of the M dwarf planet hosts that will be uncovered by upcoming exoplanet surveys.
14280. SpeX spectroscopy of low mass binaries. I.
ID:
ivo://CDS.VizieR/J/ApJ/710/1142
Title:
SpeX spectroscopy of low mass binaries. I.
Short Name:
J/ApJ/710/1142
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the identification of 17 candidate brown dwarf binaries whose components straddle the L dwarf/T dwarf transition. These sources were culled from a large near-infrared spectral sample of L and T dwarfs observed with the Infrared Telescope Facility SpeX spectrograph. Candidates were selected on the basis of spectral ratios which segregate known (resolved) L dwarf/T dwarf pairs from presumably single sources. Composite templates, constructed by combining 13581 pairs of absolute flux-calibrated spectra, are shown to provide statistically superior fits to the spectra of our 17 candidates as compared to single templates. Ten of these candidates appear to have secondary components that are significantly brighter than their primaries over the 1.0-1.3um band, indicative of rapid condensate depletion at the L dwarf/T dwarf transition. Our results support prior indications of enhanced multiplicity amongst early-type T dwarfs; 53+/-7% of the T0-T4 dwarfs in our spectral sample are found to be either resolved or unresolved (candidate) pairs, although this is consistent with an intrinsic (volume complete) brown dwarf binary fraction of only 15%. If verified, this sample of spectral binaries more than doubles the number of known L dwarf/T dwarf transition pairs, enabling a broader exploration of this poorly understood phase of brown dwarf atmospheric evolution.

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