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931. Low-mass black holes in Sy1 galaxies. II. SDSS-DR7
ID:
ivo://CDS.VizieR/J/ApJS/235/40
Title:
Low-mass black holes in Sy1 galaxies. II. SDSS-DR7
Short Name:
J/ApJS/235/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) is presented with black hole masses in the range of (1-20)x10^5^M_{sun}_. The AGNs are selected through a systematic search among galaxies in the Seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS), and careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from SDSS DR4 makes it the largest LMBH sample so far, totaling over 500 objects. Some of the statistical properties of the combined LMBH AGN sample are briefly discussed in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [OIII] luminosity. The effective optical-to-X-ray spectral indices {alpha}_OX_, albeit with a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L_2500{AA}_. Interestingly, a correlation of {alpha}_OX_ with black hole mass is also found, with {alpha}OX being statistically flatter (stronger X-ray relative to optical) for lower black hole masses. Only 26 objects, mostly radio loud, were detected in radio at 20cm in the FIRST survey, giving a radio-loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 10^8.8^-10^12.4^M_{sun}_ and optical colors typical of Sbc spirals. They are dominated by young stellar populations that seem to have undergone continuous star formation history.
932. Low-mass members of Chamaeleon I
ID:
ivo://CDS.VizieR/J/ApJ/684/654
Title:
Low-mass members of Chamaeleon I
Short Name:
J/ApJ/684/654
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used images obtained with the Infrared Array Camera and the Multiband Imaging Photometer on board the Spitzer Space Telescope to search for low-mass stars and brown dwarfs with circumstellar disks in the Chamaeleon I star-forming region. Through optical spectroscopy of sources with red colors in these data, we have identified seven new disk-bearing members of the cluster. Three of these objects are probably brown dwarfs, according to their spectral types (M8, M8.5, M8-L0). Three of the other new members may have edge-on disks, based on the shapes of their infrared spectral energy distributions. One of the possible edge-on systems has a steeply rising slope from 4.5 to 24um, indicating that it could be a Class I source (star+disk+envelope) rather than a Class II source (star+disk). If so, then it would be one of the least massive known Class I protostars (M5.75, M~0.1M_{sun}_).
933. Low-mass stars in 25 Ori group and Orion OB1a
ID:
ivo://CDS.VizieR/J/AJ/154/14
Title:
Low-mass stars in 25 Ori group and Orion OB1a
Short Name:
J/AJ/154/14
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Orion OB1a sub-association is a rich low-mass star (LMS) region. Previous spectroscopic studies have confirmed 160 LMSs in the 25 Orionis stellar group (25 Ori), which is the most prominent overdensity of Orion OB1a. Nonetheless, the current census of the 25 Ori members is estimated to be lower than 50% complete, leaving a large number of members to be still confirmed. We retrieved 172 low-resolution stellar spectra in Orion OB1a observed as ancillary science in the SDSS-III/BOSS survey, for which we classified their spectral types and determined physical parameters. To determine memberships, we analyzed the H{alpha} emission, LiI{lambda}6708 absorption, and NaI{lambda}{lambda}8183,8195 absorption as youth indicators in stars classified as M type. We report 50 new LMSs spread across the 25 Orionis, ASCC18, and ASCC20 stellar groups with spectral types from M0 to M6, corresponding to a mass range of 0.10{<=}m/M_{Sun}_{<=}0.58. This represents an increase of 50% in the number of known LMSs in the area and a net increase of 20% in the number of 25 Ori members in this mass range. Using parallax values from the Gaia DR1 catalog, we estimated the distances to these three stellar groups and found that they are all co-distant, at 338+/-66pc. We analyzed the spectral energy distributions of these LMSs and classified their disks into evolutionary classes. Using H-R diagrams, we found a suggestion that 25 Ori could be slightly older than the other two observed groups in Orion OB1a.
934. Low-mass stars in {sigma} Ori and {lambda} Ori
ID:
ivo://CDS.VizieR/J/A+A/488/167
Title:
Low-mass stars in {sigma} Ori and {lambda} Ori
Short Name:
J/A+A/488/167
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10Myr) clusters {sigma} Ori and {lambda} Ori. We observed 98 and 49 low-mass (0.2-1.0M_{sun}_stars in {sigma} Ori and {lambda} Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R~17000) HR15N grating (6470-6790{AA}). We used radial velocities, Li and H{alpha} to establish cluster membership and H{alpha} and other optical emission lines to analyze the accretion properties of members. We identified 65 and 45 members of the {sigma} Ori and {lambda} Ori clusters, respectively, and discovered 16 new candidate binary systems.
935. Low-mass stars in Trumpler 37
ID:
ivo://CDS.VizieR/J/A+A/559/A3
Title:
Low-mass stars in Trumpler 37
Short Name:
J/A+A/559/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr 37. With a well-studied solar-type population, Tr 37 is a benchmark for disk evolution. We used low-resolution spectroscopy to identify and classify 141 members (78 new ones) and 64 probable members, mostly M-type stars. H{alpha} emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the spectral energy distributions (SEDs) and search for disks. We construct radiative transfer models to explore the structures of full-disks, pre-transition, transition, and dust-depleted disks.
936. Low-Mass Stars' Membership in Alpha Persei Cluster
ID:
ivo://CDS.VizieR/V/80
Title:
Low-Mass Stars' Membership in Alpha Persei Cluster
Short Name:
V/80
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog contains the tabulated results of a combined astrometric, photometric, and spectroscopic search for low-mass members in the intermediate-age open cluster Alpha Persei. It contains information on 132 new members and likely members, and 16 uncertain members of Alpha Per. The new membership information suggested to the author a revised age of the cluster to approximately 8x10+7yr. Tabulated data include AP number, VBI photometry, 1950 coordinates, relative proper motions with errors, H-alpha equivalent widths, and spectral type. Included are the individual membership determinations, based on H-alpha emission, spectral type, and echelle spectra data. The photometric data were obtained with the Lick Obs. 1-m Nickel Telescope using a TI 500x500 pixel CCD in B, V, and I bands. Low dispersion CCD spectra centered on H-alpha for candidates whose V-I photometry indicated likely membership using the Lick 1-m Nickel and 3-m Shane telescopes. High-dispersion echelle spectra were obtained for many bright candidates using the Hamilton echelle spectrographic with the Shane and Coude auxiliary telescopes.
937. Low-metallicity HII regions and galaxies
ID:
ivo://CDS.VizieR/J/A+A/462/535
Title:
Low-metallicity HII regions and galaxies
Short Name:
J/A+A/462/535
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our aims are to estimate the validity of empirical methods, such as R23, R23-P, log([NII]/H{alpha}) (N2), log[([OIII]/H{beta})/([NII]/H{alpha}] (O3N2), and log([SII]/H{alpha}) (S2), and to re-derive (or add) the calibrations of R23, N2, O3N2, and S2 indices for oxygen abundances on the basis of a large sample of galaxies with Te-based abundances. We determined the gas-phase oxygen abundance for a sample of 695 galaxies and HII regions with reliable detections of [OIII]4363, using the reliable and direct temperature-sensitive (Te) method of measuring metallicity. We selected 531 star-forming galaxies from the SDSS-DR4 database with strong emission lines, including [OIII]4363 detected at a signal-to-noise ratio higher than 5{sigma}, as well as 164 galaxies and HII regions from the literature with Te measurements. The O/H abundances were derived from a two-zone model for the temperature structure, assuming a relationship between high ionization and low ionization species.
938. Low-redshift Ly{alpha} galaxies from GALEX
ID:
ivo://CDS.VizieR/J/ApJ/711/928
Title:
Low-redshift Ly{alpha} galaxies from GALEX
Short Name:
J/ApJ/711/928
Date:
21 Oct 2021
Publisher:
CDS
Description:
We construct a sample of low-redshift Ly{alpha} emission-line selected sources from Galaxy Evolution Explorer (GALEX) grism spectroscopy of nine deep fields to study the role of Ly{alpha} emission in galaxy populations with cosmic time. Our final sample consists of 119 (141) sources selected in the redshift interval z=0.195-0.44 (z=0.65-1.25) from the FUV (NUV) channel. We classify the Ly{alpha} sources as active galactic nuclei (AGNs) if high-ionization emission lines are present in their UV spectra and as possible star-forming galaxies otherwise. We classify additional sources as AGNs using line widths for our Ly{alpha} emitter (LAE) analysis. These classifications are broadly supported by comparisons with X-ray and optical spectroscopic observations, though the optical spectroscopy identifies a small number of additional AGNs. Defining the GALEX LAE sample in the same way as high-redshift LAE samples, we show that LAEs constitute only about 5% of NUV-continuum selected galaxies at z~0.3. We also show that they are less common at z~0.3 than they are at z~3. Finally, we confirm that the z~2 Lyman break galaxies have relatively low metallicities for their luminosities, and we find that they lie in the same metallicity range as the z~0.3 Ly{alpha} galaxies.
939. Low-resolution near-infrared stellar spectra from CIBER
ID:
ivo://CDS.VizieR/J/AJ/153/84
Title:
Low-resolution near-infrared stellar spectra from CIBER
Short Name:
J/AJ/153/84
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present near-infrared (0.8-1.8{mu}m) spectra of 105 bright (m_J_<10) stars observed with the low-resolution spectrometer on the rocket-borne Cosmic Infrared Background Experiment. As our observations are performed above the Earth's atmosphere, our spectra are free from telluric contamination, which makes them a unique resource for near-infrared spectral calibration. Two-Micron All-Sky Survey photometry information is used to identify cross-matched stars after reduction and extraction of the spectra. We identify the spectral types of the observed stars by comparing them with spectral templates from the Infrared Telescope Facility library. All the observed spectra are consistent with late F to M stellar spectral types, and we identify various infrared absorption lines.
940. Low-resolution NIR spectra of zodiacal light
ID:
ivo://CDS.VizieR/J/PASJ/65/119
Title:
Low-resolution NIR spectra of zodiacal light
Short Name:
J/PASJ/65/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog contains the 278 low-resolution (R~20) near-infrared (1.8-5.3micron) spectra of diffuse sky covering a wide range of galactic and ecliptic latitudes with the Infrared Camera (IRC) on board AKARI before the exhaustion of liquid-helium (from September 2006 to May 2007). Advanced reduction methods specialized for the slit spectroscopy of diffuse sky spectra are developed for constructing this spectral catalog. Filter wheel of the IRC instrument has dark position to measure the dark current, and uncertainty due to dark current subtraction is estimated to be <3nW/m2/sr at 2micron (Tsumura & Wada, 2011PASJ...63..755T). Point sources brighter than mK(Vega)=19 were detected on the slit and masked for deriving the diffuse spectrum. It was confirmed that the brightness due to unresolved galactic stars under this detection limit is negligible (<0.5% of the sky brightness at 2.2 micron) by a Milky Way star count model (TRILEGAL; Girardi et al., 2005A&A...436..895G). Cumulative brightness contributed by unresolved galaxies can be estimated by the deep galaxy counts, being <4nW/m2/sr at K band in the case of limiting magnitude of mK=19 (Keenan et al., 2010ApJ...723...40K).