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761. IN-SYNC. I. APOGEE stellar parameters
ID:
ivo://CDS.VizieR/J/ApJ/794/125
Title:
IN-SYNC. I. APOGEE stellar parameters
Short Name:
J/ApJ/794/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Over two years, 8859 high-resolution H-band spectra of 3493 young (1-10Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of the SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. In addition, we present accurate extinctions by measuring the E(J-H) of these young stars with respect to the single-star photometric locus in the Pleiades. Finally, we identify an intrinsic stellar radius spread of about 25% for late-type stars in IC 348 using three (nearly) independent measures of stellar radius, namely, the extinction-corrected J-band magnitude, the surface gravity, and the Rsini from the rotational velocities and literature rotation periods. We exclude that this spread is caused by uncertainties in the stellar parameters by showing that the three estimators of stellar radius are correlated, so that brighter stars tend to have lower surface gravities and larger Rsini than fainter stars at the same effective temperature.
762. IN-SYNC. II. Candidate young stars in NGC 1333
ID:
ivo://CDS.VizieR/J/ApJ/799/136
Title:
IN-SYNC. II. Candidate young stars in NGC 1333
Short Name:
J/ApJ/799/136
Date:
21 Oct 2021
Publisher:
CDS
Description:
The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2Myr) stars in NGC 1333 is 0.92+/-0.12km/s after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a subvirial velocity dispersion of 0.5km/s. Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70{mu}G magnetic field acting on the dense cores or be the signature of a cluster with initial substructure undergoing global collapse.
763. IN-SYNC. IV. YSOs in Orion A
ID:
ivo://CDS.VizieR/J/ApJ/818/59
Title:
IN-SYNC. IV. YSOs in Orion A
Short Name:
J/ApJ/818/59
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the Sloan Digital Sky Survey APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high-resolution near-infrared spectroscopy of about 2700 young pre-main-sequence stars on a ~6{deg} field of view. We have measured accurate stellar parameters (T_eff_, logg, vsini) and extinctions and placed the sources in the Hertzsprung-Russel diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results to assess the performance and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium: we estimate an average R_V_=5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity-inferred ages and between extinction and disk presence; this strongly suggests a real spread of ages larger than a few Myr. Focusing on the young population around NGC 1980/{iota} Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (~5Myr) age and low A_V_, but considering that its radial velocity distribution is indistinguishable from Orion A's population, we suggest that NGC 1980 is part of Orion A's star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works.
764. IN-SYNC. VIII. YSOs in NGC 1333, IC 348 and Orion A
ID:
ivo://CDS.VizieR/J/ApJ/869/72
Title:
IN-SYNC. VIII. YSOs in NGC 1333, IC 348 and Orion A
Short Name:
J/ApJ/869/72
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we address two issues related to primordial disk evolution in three clusters (NGC1333, IC348, and OrionA) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC348 and OrionA is that primordial disks around intermediate-mass stars (2-5M_{sun}_) evolve faster than those around loss-mass stars (0.1-1M_{sun}_), which is consistent with previous results. However, considering only low-mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Second, in the OrionA molecular cloud, in the mass range of 0.35-0.7M_{sun}_, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5{mu}m excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC1333 and IC348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1{sigma} effect.
765. Integral Field 560-680nm observation of M81
ID:
ivo://CDS.VizieR/J/A+A/576/A58
Title:
Integral Field 560-680nm observation of M81
Short Name:
J/A+A/576/A58
Date:
21 Oct 2021
Publisher:
CDS
Description:
M81 has the nearest active nucleus with broad H{alpha} emission. A detailed study of this galaxy's centre is important for understanding the innermost structure of the AGN phenomenon. Our goal is to seek previously undetected structures using additional techniques to reanalyse a data cube obtained with the GMOS-IFU installed on the Gemini North telescope (Schnorr Muller et al., 2011MNRAS.413..149S). We analysed the data cube using techniques of noise reduction, spatial deconvolution, starlight subtraction, PCA Tomography and comparison with HST images. We identified a hot bubble with T>43500K that is associated with strong emission of [NII]{lambda}5755{AA} and large [OI]{lambda}6300/H{alpha} ratio, as well as with a bluish continuum, surrounded by a thin shell of H{alpha}+[NII] emission. We also reinterpret the outflow found by Schnorr Muller et al. (2011MNRAS.413..149S) showing that the blueshifted cone nearly coincides with the radio jet, as expected. We interpret the hot bubble as likely to be caused by post starburst events that left one or more clusters of young stars, somewhat similar to the ones found at the centre of the Milky Way, like the Arches and the IRS 16 clusters. Shocked structures from combined young stellar winds or supernova remnants are probably the cause of this hot gas and the low ionization emission.
766. Integral Field Spectroscopy of 8 BCGs
ID:
ivo://CDS.VizieR/J/A+A/577/A21
Title:
Integral Field Spectroscopy of 8 BCGs
Short Name:
J/A+A/577/A21
Date:
21 Oct 2021
Publisher:
CDS
Description:
Blue Compact Galaxies (BCG) are gas rich, low luminosity, low metallicity systems, undergoing a violent burst of star formation. These galaxies offer us a unique opportunity to investigate collective star formation and its effects on galaxy evolution in a relatively simple environment. Spatially resolved spectrophotometric studies of BCGs are essential for a better understanding of the role of starburst-driven feedback processes on the kinematical and chemical evolution of low-mass galaxies near and far. We carry out an integral field spectroscopic study of a sample of BCGs, with the aim to probe the morphology, kinematics, dust extinction, and excitation mechanisms of their warm interstellar medium. Eight BCGs were observed with the VIMOS integral field unit at the Very Large Telescope using blue and orange grisms in high resolution mode. At a spatial sampling of 0.67 per spaxel we covered about 30x30-arcsec on the sky, with a wavelength range of 4150...7400{AA}. Emission lines were fitted with a single Gaussian profiles to measure their wavelength, flux, and width. From these data we built two-dimensional maps of the continuum and the most prominent emission-lines, as well as diagnostic line ratios, extinction, and kinematic maps. An atlas of emission-line fluxes and continuum emission; ionization, interstellar extinction, and electron density maps from line ratios; velocity and velocity dispersion fields. Additionally, from integrated spectroscopy, tables of the extinction corrected line fluxes and equivalent widths, diagnostic-line ratios, physical parameters and abundances for the brightest star-forming knots and for the whole galaxy.
767. Integrated spectroscopy of HRS galaxies
ID:
ivo://CDS.VizieR/J/A+A/550/A114
Title:
Integrated spectroscopy of HRS galaxies
Short Name:
J/A+A/550/A114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present long-slit integrated spectroscopy of 238 late-type galaxies belonging to the Herschel Reference Survey, a volume-limited sample representative of the nearby universe. This sample has a unique legacy value since it was ideally defined for any statistical study of the multifrequency properties of galaxies spanning a wide range in morphological type and luminosity. The spectroscopic observations cover the spectral range 3600-6900{AA} at a resolution R~=1000 and are thus suitable for separating both the underlying absorption from the emission of the H{beta} line and the two [NII] lines from the H{alpha} emission. We measured the fluxes and the equivalent widths of the strongest emission lines ([OII]{lambda}3727, H{beta}, [OIII]{lambda}4959 and [OIII]{lambda}5007, [NII]{lambda}6548, H{alpha}, [NII]{lambda}6584, [SII]{lambda}6717, and [SII]{lambda}6731). We used the data to study the distribution of the equivalent width of all the emission lines, of the Balmer decrement C(H{beta}), and of the observed underlying Balmer absorption under H{beta} (EWH{beta}_abs_) in this sample. Combining these new spectroscopic data with those available at other frequencies, we also study the dependence of C(H{beta}) and EWH{beta}_abs_ on morphological type, stellar mass, stellar surface density, star formation rate, birthrate parameter, and metallicity in galaxies belonging to different environments (fields vs. Virgo cluster). The distribution of the equivalent width of all the emission lines, of C(H{beta}) (or equivalently of A(H{alpha}), and of EWH{beta}_abs_ are systematically different in cluster and field galaxies. The Balmer decrement increases with the stellar mass, stellar surface density, metallicity, and star formation rate of the observed galaxies, while it is unexpectedly almost independent of the column density of the atomic and molecular gas. The dependence of C(H{beta}) on stellar mass is steeper than previously found in other works. The underlying Balmer absorption does not significantly change with any of these physical parameters.
768. Intergalac. medium opacity from Lyman-break galaxies
ID:
ivo://CDS.VizieR/J/AJ/160/37
Title:
Intergalac. medium opacity from Lyman-break galaxies
Short Name:
J/AJ/160/37
Date:
08 Dec 2021
Publisher:
CDS
Description:
We measure the effective opacity ({tau}_eff_) of the intergalactic medium from the composite spectra of 281 Lyman-break galaxies in the redshift range 2<~z<~3. Our spectra are taken from the COSMOS Ly{alpha} Mapping And Tomographic Observations survey derived from the Low Resolution Imaging Spectrometer on the W.M. Keck I telescope. We generate composite spectra in two redshift intervals and fit them with spectral energy distribution (SED) models composed of simple stellar populations. Extrapolating these SED models into the Ly{alpha} forest, we measure the effective Ly{alpha} opacity ({tau}_eff_) in the 2.02<~z<~2.44 range. At z=2.22, we estimate {tau}_eff_=0.159{+/-}0.001 from a power-law fit to the data. These measurements are consistent with estimates from quasar analyses at z<2.5 indicating that the systematic errors associated with normalizing quasar continua are not substantial. We provide a Gaussian processes model of our results and previous {tau}_eff_ measurements that describes the steep redshift evolution in {tau}_eff_ from z=1.5-4.
769. Intermediate-line region in quasars
ID:
ivo://CDS.VizieR/J/ApJ/683/L115
Title:
Intermediate-line region in quasars
Short Name:
J/ApJ/683/L115
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on a systematic investigation of the H{beta} and FeII emission lines in a sample of 568 quasars within z<0.8 selected from the Sloan Digital Sky Survey quasar catalog (DR5, Cat. VII/252). The conventional broad H{beta} emission line can be decomposed into two components: one with intermediate velocity width and another with very broad width. The velocity shift and equivalent width of the intermediate-width component do not correlate with those of the very broad component of H{beta}, but its velocity shift and width do resemble FeII. Moreover, the width of the very broad component is roughly 2.5 times that of the intermediate-width component. These characteristics strongly suggest the existence of an intermediate-line region, whose kinematics seem to be dominated by infall, located at the outer portion of the broad-line region.
770. Intermediate-mass T Tau stars spectra
ID:
ivo://CDS.VizieR/J/A+A/622/A72
Title:
Intermediate-mass T Tau stars spectra
Short Name:
J/A+A/622/A72
Date:
21 Oct 2021
Publisher:
CDS
Description:
The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated. We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determined fundamental stellar parameters (T_eff_, L and vsini) and measured surface magnetic field characteristics (including detection limits for non-detections, and longitudinal fields and basic topologies for positive detections). Using PMS evolutionary models, we determined the mass, radius, and internal structure of these stars. We compared different PMS models to check that our determinations were not model- dependant. We then compared the magnetic characteristics of our sample accounting for their stellar parameters and internal structures. Results: We detect magnetic fields in about half of our sample. About 90% of the magnetic stars have outer convective envelopes larger than ~25% of the stellar radii, and heavier than ~2% of the stellar mass. Going to higher mass, we find that the magnetic incidence in intermediate-mass stars drops very quickly, within a time-scale of the order of few times 0.1Myr. Finally, we propose that intermediate-mass T Tauri stars with large convective envelopes, close to the fully convective limit, have complex fields and that their dipole component strengths may decrease as the sizes of their convective envelopes decrease, similar to lower-mass T Tauri stars.