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Start Over Subject infrared astronomy
601. KiDS-VIKING-450 cosmic shear
ID:
ivo://CDS.VizieR/J/A+A/633/A69
Title:
KiDS-VIKING-450 cosmic shear
Short Name:
J/A+A/633/A69
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey (VIKING). This is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning 450 deg^2^, allows us to significantly improve the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and - most importantly - to solidify our knowledge of the redshift distributions of the sources. Based on a flat LCDM model we find S_8_=0.737^+0.040^_-0.036_ in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck Legacy CMB measurements remains in this systematically more robust analysis, with S_8_ differing by 2.3{sigma}. This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys. Data products from this analysis are available at http://kids.strw.leidenuniv.nl.
602. Kinematic analysis of M7-L8 dwarfs
ID:
ivo://CDS.VizieR/J/ApJS/225/10
Title:
Kinematic analysis of M7-L8 dwarfs
Short Name:
J/ApJS/225/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color-magnitude, luminosity, and effective temperature.
603. Kinematic analysis of the Minispiral
ID:
ivo://CDS.VizieR/J/A+A/426/81
Title:
Kinematic analysis of the Minispiral
Short Name:
J/A+A/426/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained BEAR spectro-imaging data of the Galactic Center HII region "Sgr A West", also known as the "Minispiral", in the hydrogen Brackett {gamma} line (2.166 microns). Through multi-component line fitting, we have decomposed this HII region into nine overlapping velocity structures, for which we have extracted the line flux and radial velocity maps. We have then fitted a set of Keplerian orbits onto the radial velocity map of the most extended structure (the "Northern Arm"), assuming that it was orbiting the central black hole candidate Sgr A*. This fit allows us to propose a three-dimensional kinematic model for this structure, which is hereby given as a set of FITS files. In this model, the central mass, its location in the field, and the distance to the Galactic Center are fixed: we use a mass of 3e6 solar masses and a distance of 8kpc; the pixel scale is 0.353 arcsec/pix, Sgr A* is considered to be located at pixel (59.2538, 38.9849) (IDL notation: (0, 0) is the center of the lower-left pixel, add 1 for FITS convention).
604. Kinematic data of 3 nearby low-mass galaxies
ID:
ivo://CDS.VizieR/J/ApJ/858/118
Title:
Kinematic data of 3 nearby low-mass galaxies
Short Name:
J/ApJ/858/118
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed study of the nuclear star clusters (NSCs) and massive black holes (BHs) of four of the nearest low-mass early-type galaxies: M32, NGC 205, NGC 5102, and NGC 5206. We measure the dynamical masses of both the BHs and NSCs in these galaxies using Gemini/NIFS or VLT/SINFONI stellar kinematics, Hubble Space Telescope (HST) imaging, and Jeans anisotropic models. We detect massive BHs in M32, NGC 5102, and NGC 5206, while in NGC 205, we find only an upper limit. These BH mass estimates are consistent with previous measurements in M32 and NGC 205, while those in NGC 5102 and NGC 5206 are estimated for the first time and both found to be <10^6^M_{sun}_. This adds to just a handful of galaxies with dynamically measured sub-million M_{sun}_ central BHs. Combining these BH detections with our recent work on NGC 404's BH, we find that 80% (4/5) of nearby, low-mass (10^9^-10^10^M_{sun}_; {sigma}_*_~20-70km/s) early-type galaxies host BHs. Such a high occupation fraction suggests that the BH seeds formed in the early epoch of cosmic assembly likely resulted in abundant seeds, favoring a low-mass seed mechanism of the remnants, most likely from the first generation of massive stars. We find dynamical masses of the NSCs ranging from 2 to 73x10^6^M_{sun}_ and compare these masses to scaling relations for NSCs based primarily on photometric mass estimates. Color gradients suggest that younger stellar populations lie at the centers of the NSCs in three of the four galaxies (NGC 205, NGC 5102, and NGC 5206), while the morphology of two are complex and best fit with multiple morphological components (NGC 5102 and NGC 5206). The NSC kinematics show they are rotating, especially in M32 and NGC 5102 (V/{sigma}_*_~0.7).
605. Kinematic distance ambiguity in HII regions
ID:
ivo://CDS.VizieR/J/ApJ/753/62
Title:
Kinematic distance ambiguity in HII regions
Short Name:
J/ApJ/753/62
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity.
606. Kinematic structure of the Galactic Center S cluster
ID:
ivo://CDS.VizieR/J/ApJ/896/100
Title:
Kinematic structure of the Galactic Center S cluster
Short Name:
J/ApJ/896/100
Date:
11 Mar 2022
Publisher:
CDS
Description:
We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high-velocity S cluster and orbit the supermassive black hole Sgr A* at the center of the Milky Way. For 39 of them, orbital elements are known; for the remainder, we know proper motions. The distribution of the inclinations and the proper motion flight directions deviate significantly from a uniform distribution, which one expects if the orientation of the orbits are random. Across the central arcseconds, the S-cluster stars are arranged in two almost edge-on disks that are located at a position angle approximately +/-45{deg} with respect to the Galactic plane. The angular momentum vectors for stars in each disk point in both directions, i.e., the stars in a given disk rotate in opposite ways. The poles of this structure are located only about 25{deg} from the line of sight. This structure may be the result of a resonance process that started with the formation of the young B-dwarf stars in the cluster about 6Myr ago. Alternatively, it indicated the presence of a disturber at a distance from the center comparable to the distance of the compact stellar association IRS 13.
607. K & M giants equivalent widths
ID:
ivo://CDS.VizieR/J/A+A/328/175
Title:
K & M giants equivalent widths
Short Name:
J/A+A/328/175
Date:
21 Oct 2021
Publisher:
CDS
Description:
The analyses of high resolution infrared spectra have been done for CN lines in oxygen-rich cool evolved stars including 2 K giants, 20 M giants and 1 S-type star. Since CN lines analyzed in the present work are weak and resolved well, they are appropriate for quantitative analyses. CN lines of {DELTA}v=-2 and -1 sequences (red system) which are in the K- and the H-window regions, respectively, give the consistent nitrogen abundance for each star. The analyses of NH lines in the L-window region have been done for 5 late M giants for which CN lines have been also analyzed. Although the triplet structure of NH lines cannot be fully resolved, they are preferable because determination of nitrogen abundance is almost independent of other elemental abundances while nitrogen abundance based on CN depends on carbon abundance. The nitrogen abundances derived from NH for late M giants agree well with those from CN for which we adopt 7.75eV as the dissociation energy in the analysis. The results show that the nitrogen abundances in late M giants are larger than those in early M giants while decrease of the carbon abundance was found in late M giants by our previous work (Tsuji, 1991A&A...245..203T). These variations of abundances can not be explained by the first dredge-up model but require additional processing by the CN cycle and mixing after the first dredge-up. However, there is no obvious evidence of other processes such as the 3{alpha}-process and subsequent hot bottom burning in our program stars. Such variation of the carbon and nitrogen abundances is not well understood by the present evolutionary models of low-mass and intermediate-mass stars.
608. KMOS O-type star detection in Tr 16-SE
ID:
ivo://CDS.VizieR/J/A+A/648/A34
Title:
KMOS O-type star detection in Tr 16-SE
Short Name:
J/A+A/648/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Carina Nebula harbors a large population of high-mass stars, including at least 75 O-type and Wolf-Rayet (WR) stars, but the current census is not complete since further high-mass stars may be hidden in or behind the dense dark clouds that pervade the association. With the aim of identifying optically obscured O- and early B-type stars in the Carina Nebula, we performed the first infrared spectroscopic study of stars in the optically obscured stellar cluster Tr 16-SE, located behind a dark dust lane south of {eta} Car. We used the integral-field spectrograph KMOS at the ESO VLT to obtain H- and K-band spectra with a resolution of R~4000 ({Delta}{lambda}~5{AA}) for 45 out of the 47 possible OB candidate stars in Tr 16-SE, and we derived spectral types for these stars. We find 15 stars in Tr 16-SE with spectral types between O5 and B2 (i.e. high-mass stars with M>=8M_{sun}_), only two of which were known before. An additional nine stars are classified as (Ae)Be stars, i.e. intermediate-mass pre-main sequence stars, and most of the remaining targets show clear signatures of being late-type stars and are thus most likely foreground stars or background giants unrelated to the Carina Nebula. Our estimates of the stellar luminosities suggest that nine of the 15 O- and early B-type stars are members of Tr 16-SE, whereas the other six seem to be background objects. Our study increases the number of spectroscopically identified high-mass stars (M>=8M_{sun}_) in Tr 16-SE from two to nine and shows that Tr 16-SE is one of the larger clusters in the Carina Nebula. Our identification of three new stars with spectral types between O5 and O7 and four new stars with spectral types O9 to B1 significantly increases the number of spectroscopically identified O-type stars in the Carina Nebula.
609. KMOS view of the Galactic centre. I.
ID:
ivo://CDS.VizieR/J/A+A/584/A2
Title:
KMOS view of the Galactic centre. I.
Short Name:
J/A+A/584/A2
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic centre hosts a crowded, dense nuclear star cluster with a half-light radius of 4pc. Most of the stars in the Galactic centre are cool late-type stars, but there are also >=100 hot early-type stars in the central parsec of the Milky Way. These stars are only 3-8Myr old. Our knowledge of the number and distribution of early-type stars in the Galactic centre is incomplete. Only a few spectroscopic observations have been made beyond a projected distance of 0.5pc of the Galactic centre. The distribution and kinematics of early-type stars are essential to understand the formation and growth of the nuclear star cluster.
610. Knots in the deep [FeII]+[SiI] image of the SNR Cas A
ID:
ivo://CDS.VizieR/J/ApJ/866/139
Title:
Knots in the deep [FeII]+[SiI] image of the SNR Cas A
Short Name:
J/ApJ/866/139
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a long-exposure (~10hr), narrowband image of the supernova (SN) remnant Cassiopeia A (Cas A) centered at 1.644{mu}m emission. The passband contains [FeII] 1.644{mu}m and [SiI] 1.645{mu}m lines, and our "deep [FeII]+[SiI] image" provides an unprecedented panoramic view of Cas A, showing both shocked and unshocked SN ejecta, together with shocked circumstellar medium at subarcsecond (~0.7" or 0.012pc) resolution. The diffuse emission from the unshocked SN ejecta has a form of clumps, filaments, and arcs, and their spatial distribution correlates well with that of the Spitzer [SiII] infrared emission, suggesting that the emission is likely due to [SiI] not [FeII] as in shocked material. The structure of the optically invisible western area of Cas A is clearly seen for the first time. The area is filled with many quasi-stationary flocculi (QSFs) and fragments of the disrupted ejecta shell. We identified 309 knots in the deep [FeII]+[SiI] image and classified them into QSFs and fast-moving knots (FMKs). The comparison with previous optical plates indicates that the lifetime of most QSFs is >~60yr. The total H+He mass of QSFs is ~0.23M_{sun}_, implying that the mass fraction of dense clumps in the progenitor's mass ejection immediately prior to the SN explosion is about 4%-6%. FMKs in the deep [FeII]+[SiI] image mostly correspond to S-rich ejecta knots in optical studies, while those outside the southeastern disrupted ejecta shell appear Fe-rich. The mass of the [FeII] line emitting, shocked dense Fe ejecta is ~3x10^-5^M_{sun}_.