- ID:
- ivo://CDS.VizieR/J/ApJ/853/86
- Title:
- HST large programme on {omega} Centauri. II.
- Short Name:
- J/ApJ/853/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this second installment of the series, we look at the internal kinematics of the multiple stellar populations of the globular cluster {omega} Centauri in one of the parallel Hubble Space Telescope (HST) fields, located at about 3.5 half-light radii from the center of the cluster. Thanks to the over 15yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as ~10{mu}as/yr, and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified in our first paper are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with {eta}_1G_=-0.007+/-0.026 for the former and {eta}_2G_=0.074+/-0.029 for the latter, where {eta} is defined so that the velocity dispersion {sigma}_{mu}_ scales with stellar mass as {sigma}_{mu}_{propto}m^-{eta}^. The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in {omega} Centauri and other globular clusters.
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- ID:
- ivo://CDS.VizieR/J/ApJ/716/712
- Title:
- HST light curves of six SNe and Union2
- Short Name:
- J/ApJ/716/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z>1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/4
- Title:
- HST monitoring of flaring stars in the Galactic bulge
- Short Name:
- J/ApJ/754/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We utilize the Sagittarius Window Eclipsing Extrasolar Planet Search Hubble Space Telescope/Advanced Camera for Surveys data set for a Deep Rapid Archival Flare Transient Search (DRAFTS) to constrain the flare rate toward the older stellar population in the Galactic bulge. During seven days of monitoring 229293 stars brighter than V=29.5, we find evidence for flaring activity in 105 stars between V=20 and V=28. We divided the sample into non-variable stars and variable stars whose light curves contain large-scale variability. The flare rate on variable stars is ~700 times that of non-variable stars, with a significant correlation between the amount of underlying stellar variability and peak flare amplitude. The flare energy loss rates are generally higher than those of nearby well-studied single dMe flare stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/114
- Title:
- HST/NICMOS Galactic Center survey catalogue
- Short Name:
- J/MNRAS/417/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our Hubble Space Telescope/Near-Infrared Camera and Multi-Object Spectrometer (HST/NICMOS) Paschen {alpha} survey of the Galactic Centre, first introduced by Wang et al. (2010MNRAS.402..895W), provides a uniform, panoramic, high-resolution map of stars and an ionized diffuse gas in the central 416arcmin^2^ of the Galaxy. This survey was carried out with 144 HST orbits using two narrow-band filters at 1.87 and 1.90um in NICMOS Camera 3. In this paper, we describe in detail the data reduction and mosaicking procedures followed, including background level matching and astrometric corrections. We have detected ~570000 near-infrared (near-IR) sources using the 'starfinder' software and are able to quantify photometric uncertainties of the detections.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A10
- Title:
- HST/NICMOS III imaging in Orion Nebula Cluster
- Short Name:
- J/A+A/534/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep HST/NICMOS Camera 3 F110W and F160W imaging of a 26'x33', corresponding to 3.1x3.8pc^2^, non-contiguous field towards the Orion Nebula Cluster (ONC). The main aim is to determine the ratio of low-mass stars to brown dwarfs for the cluster as a function of radius out to a radial distance of 1.5pc. The sensitivity of the data outside the nebulous central region is F160W<=21.0mag, significantly deeper than previous studies of the region over a comparable area. We create an extinction limited sample and determine the ratio of low-mass stars (0.08-1M_{sun}_) to brown dwarfs (0.02-0.08M_{sun}_ and 0.03-0.08M_{sun}_) for the cluster as a whole and for several annuli. The ratio found for the cluster within a radius of 1.5pc is R_02_=N(0.08-1M_{sun}_)/N(0.02-0.08M_{sun}_)=1.7+/-0.2, and R_03_=N(0.08-1M_{sun}_)/N(0.03-0.08M_{sun}_)=2.4+/-0.2, after correcting for field stars. The ratio for the central 0.3x0.3pc^2^ region down to 0.03M_{sun}_ was previously found to be R_03_=3.3^+0.8^_-0.7_, suggesting the low-mass content of the cluster is mass segregated. We discuss the implications of a gradient in the ratio of stars to brown dwarfs in the ONC in the context of previous measurements of the cluster and for other nearby star forming regions. We further discuss the current evidence for variations in the low-mass IMF and primordial mass segregation.
- ID:
- ivo://CDS.VizieR/J/ApJ/730/125
- Title:
- HST/NICMOS observations of bright IR galaxies
- Short Name:
- J/ApJ/730/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results on the physical nature of infrared-luminous sources at 0.5<z<2.8 as revealed by HST/NICMOS imaging and Infrared Spectrograph mid-infrared spectroscopy. Our sample consists of 134 galaxies selected at 24um with a flux of S(24um)>0.9mJy. We find many (~60%) of our sources to possess an important bulge and/or central point source component, most of which reveal additional underlying structures after subtraction of a best-fit Sersic (or Sersic+PSF) profile. Based on visual inspection of the NIC2 images and their residuals, we estimate that ~80% of all our sources are mergers. We calculate lower and upper limits on the merger fraction to be 62% and 91%, respectively. At z<1.5, we observe objects in early (pre-coalescence) merging stages to be mostly disk and star formation dominated, while we find mergers to be mainly bulge dominated and active galactic nucleus (AGN)-starburst composites during coalescence and then AGN dominated in late stages. This is analogous to what is observed in local ULIRGs. Finally, we observe obscured ({tau}_9.7um_>3.36) quasars to live in faint and compact hosts and show that these are likely high-redshift analogs of local dense-core mergers. We find late-stage mergers to possess predominantly unobscured AGN spectra, but do not observe other morphological classes to carry any specific combination of {tau}_9.7um_ and polycyclic aromatic hydrocarbon (PAH) equivalent width.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/85
- Title:
- HST observations for LMC Cepheids
- Short Name:
- J/ApJ/876/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an improved determination of the Hubble constant from Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud (LMC). These were obtained with the same WFC3 photometric system used to measure extragalactic Cepheids in the hosts of SNe Ia. Gyroscopic control of HST was employed to reduce overheads while collecting a large sample of widely separated Cepheids. The Cepheid period-luminosity relation provides a zero-point-independent link with 0.4% precision between the new 1.2% geometric distance to the LMC from detached eclipsing binaries (DEBs) measured by Pietrzynski+ (2019Natur.567..200P) and the luminosity of SNe Ia. Measurements and analysis of the LMC Cepheids were completed prior to knowledge of the new DEB LMC distance. Combined with a refined calibration of the count-rate linearity of WFC3-IR with 0.1% precision, these three improved elements together reduce the overall uncertainty in the geometric calibration of the Cepheid distance ladder based on the LMC from 2.5% to 1.3%. Using only the LMC DEBs to calibrate the ladder, we find H_0_=74.22+/-1.82km/s/Mpc including systematic uncertainties, 3% higher than before for this particular anchor. Combining the LMC DEBs, masers in NGC 4258, and Milky Way parallaxes yields our best estimate: H_0_=74.03+/-1.42km/s/Mpc, including systematics, an uncertainty of 1.91%-15% lower than our best previous result. Removing any one of these anchors changes H0 by less than 0.7%. The difference between H0 measured locally and the value inferred from Planck CMB and {Lambda}CDM is 6.6+/-1.5km/s/Mpc or 4.4{sigma} (P=99.999% for Gaussian errors) in significance, raising the discrepancy beyond a plausible level of chance. We summarize independent tests showing that this discrepancy is not attributable to an error in any one source or measurement, increasing the odds that it results from a cosmological feature beyond {Lambda}CDM.
- ID:
- ivo://CDS.VizieR/J/ApJ/746/88
- Title:
- HST observations of GCs in NGC 1399
- Short Name:
- J/ApJ/746/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine new Wide Field Camera 3 IR Channel (WFC3/IR) F160W (H_160_) imaging data for NGC 1399, the central galaxy in the Fornax cluster, with archival F475W (g_475_), F606W (V_606_), F814W (I_814_), and F850LP (z _850_) optical data from the Advanced Camera for Surveys (ACS). The purely optical g_475_-I_814_, V_606_-I_814_, and g_475_-z_850_colors of NGC 1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes I_814_>21.5. The optical-IR I_814_-H_160_ color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V_606_-H_160_ colors show marginal evidence for bimodality, consistent with bimodality in V_606_-I_814_ and unimodality in I_814_-H_160_.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/68
- Title:
- HST observations of low-mass BH host galaxies
- Short Name:
- J/ApJ/742/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope observations of 147 host galaxies of low-mass black holes (BHs), we systematically study the structures and scaling relations of these active galaxies. Our sample is selected to have central BHs with virial masses of ~10^5^-10^6^M_{sun}_. The host galaxies have total I-band magnitudes of -23.2<M_I_<-18.8mag and bulge magnitudes of -22.9<M_I_<-16.1mag. Detailed bulge-disk-bar decompositions with GALFIT show that 93% of the galaxies have extended disks, 39% have bars, and 5% have no bulges at all at the limits of our observations. Based on the Sersic index and bulge-to-total ratio, we conclude that the majority of the galaxies with disks are likely to contain pseudobulges and very few of these low-mass BHs live in classical bulges. The fundamental plane of our sample is offset from classical bulges and ellipticals in a way that is consistent with the scaling relations of pseudobulges. The sample has smaller velocity dispersion at fixed luminosity in the Faber-Jackson plane compared with classical bulges and elliptical galaxies. The galaxies without disks are structurally more similar to spheroidals than to classical bulges according to their positions in the fundamental plane, especially the Faber-Jackson projection. Overall, we suggest that BHs with mass <~10^6^M_{sun}_ live in galaxies that have evolved secularly over the majority of their history. A classical bulge is not a prerequisite to host a BH.
- ID:
- ivo://CDS.VizieR/J/AJ/142/187
- Title:
- HST observations of 7 Pop.II variable stars
- Short Name:
- J/AJ/142/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new absolute trigonometric parallaxes and proper motions for seven Population II variable stars - five RR Lyr variables: RZ Cep, XZ Cyg, SU Dra, RR Lyr, and UV Oct; and two type 2 Cepheids: VY Pyx and {kappa} Pav. We obtained these results with astrometric data from Fine Guidance Sensors, white-light interferometers on Hubble Space Telescope. We find absolute parallaxes in milliseconds of arc: RZ Cep, 2.12+/-0.16mas; XZ Cyg, 1.67+/-0.17mas; SU Dra, 1.42+/-0.16mas; RR Lyr, 3.77+/-0.13mas; UV Oct, 1.71+/-0.10mas; VY Pyx, 6.44+/-0.23mas; and {kappa} Pav, 5.57+/-0.28mas; an average {sigma}_{pi}_/{pi}=5.4%. With these parallaxes, we compute absolute magnitudes in V and K bandpasses corrected for interstellar extinction and Lutz-Kelker-Hanson bias. Using these RR Lyrae variable star absolute magnitudes, we then derive zero points for M_V_-[Fe/H] and M_K_-[Fe/H]-logP relations. The technique of reduced parallaxes corroborates these results. We employ our new results to determine distances and ages of several Galactic globular clusters and the distance of the Large Magellanic Cloud. The latter is close to that previously derived from Classical Cepheids uncorrected for any metallicity effect, indicating that any such effect is small. We also discuss the somewhat puzzling results obtained for our two type 2 Cepheids.
