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781. Circumstellar disk candidates in Orion
ID:
ivo://CDS.VizieR/J/AJ/119/3026
Title:
Circumstellar disk candidates in Orion
Short Name:
J/AJ/119/3026
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an optical study of four 45'x45' fields centered ~0.5{deg} east, west, north, and south of the Orion Nebula Cluster center. We have measured V and I_C_ photometry for ~5000 stars, and U photometry for ~1600 of these. We have obtained spectral classifications for ~300 of the stars with UVI_C_ photometry plus an additional ~200 stars located outside the area of our photometric survey. Dereddened photometry allows us to investigate the evidence for circumstellar accretion disks from excess emission at ultraviolet wavelengths, as well as the mass and age distributions of our sample. We find ~230 active accretion disk candidates and estimate the accretion disk fraction at >~40%. We use the magnitude of the ultraviolet excess to infer disk accretion rates. The mass accretion rate (dM/dt) decreases slowly with age over the limited age range spanned by our data, 1-3Myr, and increases slowly with mass over the limited mass range 0.2-1.2 M_{sun}_.
782. Circumstellar disk evolution in NGC 2068/71
ID:
ivo://CDS.VizieR/J/AJ/135/966
Title:
Circumstellar disk evolution in NGC 2068/71
Short Name:
J/AJ/135/966
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the disk and accretion properties of young stars in the NGC 2068 and NGC 2071 clusters. Using low-resolution optical spectra, we define a membership sample and determine an age for the region of ~2Myr. Using high-resolution spectra of the H{alpha} line we study the accretion activity of these likely members and also examine the disk properties of the likely members using IRAC and MIPS mid-infrared photometry. A substantial fraction (79%) of the 67 members have an infrared excess while all of the stars with significant infrared excess show evidence for active accretion. We find three populations of evolved disks (IRAC weak, MIPS weak, and transition disks) all of which show decreased accretion activity in addition to the evidence for evolution in the dust disk.
783. Circumstellar disks in Lupus complex
ID:
ivo://CDS.VizieR/J/A+A/642/A86
Title:
Circumstellar disks in Lupus complex
Short Name:
J/A+A/642/A86
Date:
21 Oct 2021
Publisher:
CDS
Description:
Previous star formation studies have, out of necessity, often defined a population of young stars confined to the proximity of a molecular cloud. Gaia allows us to examine a wider, three-dimensional structure of nearby star forming regions, leading to a new understanding of their history. We present a wide-area survey covering 494 deg^2^ of the Lupus complex, a prototypical low-mass star forming region. Our survey includes all known molecular clouds in this region as well as parts of the Upper Scorpius and Upper Centaurus Lupus (UCL) groups of the Sco-Cen complex. We combine Gaia DR2 proper motions and parallaxes as well as ALLWISE mid-infrared photometry to select young stellar objects (YSOs) with disks. The YSO ages are inferred from Gaia color-magnitude diagrams, and their evolutionary stages from the slope of the spectral energy distributions. We find 98 new disk-bearing sources. Our new sample includes objects with ages ranging from 1 to 15Myr and masses ranging from 0.05 to 0.5M_{sun}_, and consists of 56 sources with thick disks and 42 sources with anemic disks. While the youngest members are concentrated in the clouds and at distances of 160 pc, there is a distributed population of slightly older stars that overlap in proper motion, spatial distribution, distance, and age with the Lupus and UCL groups. The spatial and kinematic properties of the new disk-bearing YSOs indicate that Lupus and UCL are not distinct groups. Our new sample comprises some of the nearest disks to Earth at these ages, and thus provides an important target for follow-up studies of disks and accretion in very low mass stars, for example with ALMA and ESO-VLT X-shooter.
784. Circumstellar-interacting supernovae
ID:
ivo://CDS.VizieR/J/A+A/580/A131
Title:
Circumstellar-interacting supernovae
Short Name:
J/A+A/580/A131
Date:
21 Oct 2021
Publisher:
CDS
Description:
Some circumstellar-interacting (CSI) supernovae (SNe) are produced by the explosions of massive stars that have lost mass shortly before the SN explosion. There is evidence that the precursors of some SNe IIn were luminous blue variable (LBV) stars. For a small number of CSI SNe, outbursts have been observed before the SN explosion. Eruptive events of massive stars are named SN impostors (SN IMs) and whether they herald a forthcoming SN or not is still unclear. The large variety of observational properties of CSI SNe suggests the existence of other progenitors, such as red supergiant (RSG) stars with superwinds. Furthermore, the role of metallicity in the mass loss of CSI SN progenitors is still largely unexplored. Our goal is to gain insight into the nature of the progenitor stars of CSI SNe by studying their environments, in particular the metallicity at their locations. We obtain metallicity measurements at the location of 60 transients (including SNe IIn, SNe Ibn, and SN IMs) via emission-line diagnostic on optical spectra obtained at the Nordic Optical Telescope and through public archives. Metallicity values from the literature complement our sample. We compare the metallicity distributions among the different CSI SN subtypes, and to those of other core-collapse SN types. We also search for possible correlations between metallicity and CSI SN observational properties. We find that SN IMs tend to occur in environments with lower metallicity than those of SNe IIn. Among SNe IIn, SN IIn-L(1998S-like) SNe show higher metallicities, similar to those of SNe IIL/P, whereas long-lasting SNe IIn (1988Z-like) show lower metallicities, similar to those of SN IMs. The metallicity distribution of SNe IIn can be reproduced by combining the metallicity distributions of SN IMs (which may be produced by major outbursts of massive stars like LBVs) and SNe IIP (produced by RSGs). The same applies to the distributions of the normalized cumulative rank (NCR) values, which quantifies the SN association to HII regions. For SNe IIn, we find larger mass-loss rates and higher CSM velocities at higher metallicities. The luminosity increment in the optical bands during SN IM outbursts tend to be larger at higher metallicity, whereas the SN IM quiescent optical luminosities tend to be lower. The difference in metallicity between SNe IIn and SN IMs indicates that LBVs are only one of the progenitor channels for SNe IIn, with 1988Z-like and 1998S-like SNe possibly arising from LBVs and RSGs, respectively. Finally, even though line-driven winds likely do not primarily drive the late mass-loss of CSI SN progenitors, metallicity has some impact on the observational properties of these transients.
785. CIV broad abs. line SDSS QSO obs. with Gemini
ID:
ivo://CDS.VizieR/J/ApJ/862/22
Title:
CIV broad abs. line SDSS QSO obs. with Gemini
Short Name:
J/ApJ/862/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We isolate a set of quasars that exhibit emergent CIV broad absorption lines (BALs) in their spectra by comparing spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 and the SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. We find an emergence rate consistent with the previously reported disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL quasars in the SDSS. We find that candidate newly emerged BALs are preferentially drawn from among BALs with smaller balnicity indices, shallower depths, larger velocities, and smaller widths. Within two rest-frame years (average) after a BAL has emerged, we find it equally likely to continue increasing in equivalent width in an observation 6 months later (average) as it is to start decreasing. From the time separations between our observations, we conclude that the coherence timescale of BALs is less than 100 rest-frame days. We observe coordinated variability among pairs of troughs in the same quasar, likely due to clouds at different velocities responding to the same changes in ionizing flux, and the coordination is stronger if the velocity separation between the two troughs is smaller. We speculate that the latter effect may be due to clouds having on average lower densities at higher velocities owing to mass conservation in an accelerating flow, causing the absorbing gas in those clouds to respond on different timescales to the same ionizing flux variations.
786. CIV NAL systems from SDSS-DR14 quasar spectra
ID:
ivo://CDS.VizieR/J/ApJS/239/23
Title:
CIV NAL systems from SDSS-DR14 quasar spectra
Short Name:
J/ApJS/239/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the quasar spectra from the Sloan Digital Sky Survey, all with two-epoch to six-epoch observations, we search for CIV{lambda}{lambda}1548,1551 narrow absorption doublets in spectral data from the blue wing {upsilon}r=30000km/s until the red wing of CIV{lambda}1549 emission lines. We have obtained 21239 CIV narrow absorption line (NAL) systems, of which 647 systems were significantly changed on timescales from {Delta}MJD=0.24 to 1842.38 days at rest-frame. Both samples of the C IV NAL systems with multi-epoch observations and the variable C IV NAL systems are the largest ones to date. The offset velocity distribution of the variable C IV NALs from quasars has a peak at {upsilon}r~2000km/s and gently extends to a larger offset velocity. There are 110 variable C IV NALs with {upsilon}r>12000km/s. In addition, about 10% intrinsic C IV NALs show time variability on a timescale of <2000 days. We find that the variations of C IV NALs are positively or negatively correlated with the alternations of quasar continua. The two kinds of correlations suggest that the variable C IV NALs included in our absorber catalog can be classified into at least two populations: (1) highly ionized systems that are dominated by highly ionized absorbing gas and negatively respond to the fluctuations of quasar emissions; and (2) lowly ionized systems that are dominated by lowly ionized absorbing gas and positively respond to fluctuations of quasar emissions. We also find that the absolute fractional changes in the absorption strengths of C IV NALs are inversely correlated with absorption strengths.
787. CIV narrow absorption line systems in SDSS-DR14
ID:
ivo://CDS.VizieR/J/ApJS/236/39
Title:
CIV narrow absorption line systems in SDSS-DR14
Short Name:
J/ApJS/236/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
We assemble 207 variable quasars from the Sloan Digital Sky Survey, all with at least 3 observations, to analyze CIV narrow absorption doublets, and obtain 328 CIV narrow absorption line systems. We find that 19 out of 328 CIV narrow absorption line systems were changed by |{Delta}W_r_^{lambda}1548^|>=3{sigma}_{Delta}Wr_^{lambda}1548^ on timescales from 15.9 to 1477 days at rest-frame. Among the 19 obviously variable CIV systems, we find that (1) 14 systems have relative velocities {upsilon}_r_>0.01c and 4 systems have {upsilon}_r_>0.1c, where c is the speed of light; (2) 13 systems are accompanied by other variable CIV systems; (3) 9 systems were changed continuously during multiple observations; and (4) 1 system with {upsilon}_r_=16862km/s was enhanced by {Delta}W_r_^{lambda}1548^=2.7{sigma}_{Delta}Wr_^{lambda}1548^ in 0.67 day at rest-frame. The variations of absorption lines are inversely correlated with the changes in the ionizing continuum. We also find that large variations of CIV narrow absorption lines are form differently over a short timescale.
788. CLAMATO DR1: 3D Ly{alpha} forest tomography
ID:
ivo://CDS.VizieR/J/ApJS/237/31
Title:
CLAMATO DR1: 3D Ly{alpha} forest tomography
Short Name:
J/ApJS/237/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Faint star-forming galaxies at z~2-3 can be used as alternative background sources to probe the Ly{alpha} forest in addition to quasars, yielding high sightline densities that enable 3D tomographic reconstruction of the foreground absorption field. Here, we present the first data release from the COSMOS Ly{alpha} Mapping And Tomography Observations (CLAMATO) Survey, which was conducted with the LRIS spectrograph on the Keck I telescope. Over an observational footprint of 0.157deg^2^ within the COSMOS field, we used 240 galaxies and quasars at 2.17<z<3.00, with a mean comoving transverse separation of 2.37h^-1^Mpc, as background sources probing the foreground Ly{alpha} forest absorption at 2.05<z<2.55. The Ly{alpha} forest data was then used to create a Wiener-filtered tomographic reconstruction over a comoving volume of 3.15x10^5^h^-3^Mpc^3^ with an effective smoothing scale of 2.5h^-1^Mpc. In addition to traditional figures, this map is also presented as a virtual-reality visualization and manipulable interactive figure. We see large overdensities and underdensities that visually agree with the distribution of coeval galaxies from spectroscopic redshift surveys in the same field, including overdensities associated with several recently discovered galaxy protoclusters in the volume. Quantitatively, the map signal-to-noise is S/N^wiener^~3.4 over a 3h^-1^Mpc top-hat kernel based on the variances estimated from the Wiener filter. This data release includes the redshift catalog, reduced spectra, extracted Ly{alpha} forest pixel data, and reconstructed tomographic map of the absorption.
789. CLASH-VLT: the FF cluster MACS J0416.1-2403
ID:
ivo://CDS.VizieR/J/ApJS/224/33
Title:
CLASH-VLT: the FF cluster MACS J0416.1-2403
Short Name:
J/ApJS/224/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields (FF) cluster MACS J0416.1-2403 (z=0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ~600arcmin^2^, including ~800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ~2.2r_200_ (~4Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster (M_200_~0.9x10^15^M_{sun}_ and {sigma}_V,r200_~1000km/s) presenting two major features: (i) a bimodal velocity distribution, showing two central peaks separated by {Delta}V_rf_~1100km/s with comparable galaxy content and velocity dispersion, and (ii) a projected elongation of the main substructures along the NE-SW direction, with a prominent sub-clump ~600kpc SW of the center and an isolated BCG approximately halfway between the center and the SW clump. We also detect a low-mass structure at z~0.390, ~10' south of the cluster center, projected at ~3Mpc, with a relative line-of-sight velocity of {Delta}V_rf_~-1700km/s. The cluster mass profile that we obtain through our dynamical analysis deviates significantly from the "universal" NFW, being best fit by a Softened Isothermal Sphere model instead. The mass profile measured from the galaxy dynamics is found to be in relatively good agreement with those obtained from strong and weak lensing, as well as with that from the X-rays, despite the clearly unrelaxed nature of the cluster. Our results reveal an overall complex dynamical state of this massive cluster and support the hypothesis that the two main subclusters are being observed in a pre-collisional phase, in agreement with recent findings from radio and deep X-ray data. In this article, we also release the entire redshift catalog of 4386 sources in the field of this cluster, which includes 60 identified Chandra X-ray sources and 105 JVLA radio sources.
790. Classical Cepheids in MCs. I. LMC disk
ID:
ivo://CDS.VizieR/J/ApJ/832/176
Title:
Classical Cepheids in MCs. I. LMC disk
Short Name:
J/ApJ/832/176
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed investigation of the Large Magellanic Cloud (LMC) disk using classical Cepheids. Our analysis is based on optical (I, V; OGLE-IV), near-infrared (NIR: J, H, K_S_) and mid-infrared (MIR: w1; WISE) mean magnitudes. By adopting new templates to estimate the NIR mean magnitudes from single-epoch measurements, we build the currently most accurate, largest, and homogeneous multi-band data set of LMC Cepheids. We determine Cepheid individual distances using optical and NIR Period-Wesenheit relations (PWRs), to measure the geometry of the LMC disk and its viewing angles. Cepheid distances based on optical PWRs are precise at 3%, but accurate to 7%, while the ones based on NIR PWRs are more accurate (to 3%), but less precise (2%-15%), given the higher photometric error on the observed magnitudes. We found an inclination of i=25.05+/-0.02(stat.)+/-0.55(syst.){deg}, and a position angle of the lines of nodes P.A.=150.76+/-0.02(stat.)+/-0.07(syst.){deg}. These values agree well with estimates based either on young (Red Supergiants) or on intermediate-age (Asymptotic Giant Branch, Red Clump) stellar tracers, but they significantly differ from evaluations based on old (RR Lyrae) stellar tracers. This indicates that young/intermediate and old stellar populations have different spatial distributions. Finally, by using the reddening-law fitting approach, we provide a reddening map of the LMC disk, which is 10 times more accurate and 2 times larger than similar maps in the literature. We also found an LMC true distance modulus of {mu}_0,LMC_=18.48+/-0.10(stat. and syst.)mag, in excellent agreement with the currently most accurate measurement.