- ID:
- ivo://jvo/isas/darts/halca/halca_vsop_correlated_data
- Title:
- HALCA VSOP (the VLBI Space Observatory Programme) Correlated Data
- Short Name:
- HALCA
- Date:
- 19 Oct 2021 07:12:04
- Publisher:
- JVO
- Description:
- The VSOP (VLBI Space Observatory Programme) mission was led by the Institute of Space and Astronautical Science, in collaboration with the National Astronomical Observatory of Japan with international collaboration with NSAS, CSA, JIVE and the world radio telescopes in 14 countries. This mission provided a dedicated space radio telescope "HALCA" launched in February 1997, and carried out high-resolution observations at 1.6, 5.0, and 22 GHz with ground radio observatories to perform Very Long Baseline Interferometry (VLBI) on baselines of up to 2.6 Earth diameters. The observations are continued till 2003, and HALCA finished its operation in 2005.
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- ID:
- ivo://CDS.VizieR/J/ApJ/877/103
- Title:
- Half-mass radii for ~7000 galaxies at 1.0<=z<=2.5
- Short Name:
- J/ApJ/877/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial mass-to-light ratio gradients cause the half-mass and half-light radii of galaxies to differ, potentially biasing studies that use half-light radii. Here we present the largest catalog to date of galaxy half-mass radii at z>1: 7006 galaxies in the CANDELS fields at 1.0<=z<=2.5. The sample includes both star-forming and quiescent galaxies with stellar masses 9.0<=log(M_*_/M_{sun}_)<=11.5. We test three methods for calculating half-mass radii from multiband PSF-matched Hubble Space Telescope (HST) imaging: two based on spatially resolved spectral energy distribution modeling, and one that uses a rest-frame color profile. All three methods agree, with scatter <~0.3dex. In agreement with previous studies, most galaxies in our sample have negative color gradients (the centers are redder than the outskirts, and r_e,mass_<r_e,light_). We find that color gradient strength has significant trends with increasing stellar mass, half-light radius, U-V color, and stellar mass surface density. These trends have not been seen before at z>1. Furthermore, color gradients of star-forming and quiescent galaxies show a similar redshift evolution: they are flat at z>~2, then steeply decrease as redshift decreases. This affects the galaxy mass-size relation. The normalizations of the star-forming and quiescent r_mass_-M_*_ relations are 10%-40% smaller than the corresponding r_light_-M_*_ relations; the slopes are ~0.1-0.3dex shallower. Finally, the half-mass radii of star-forming and quiescent galaxies at M_*_=10^10.5^M_{sun}_ only grow by ~1% and ~8% between z~2.25 and z~1.25. This is significantly less than the ~37% and ~47% size increases found when using the half-light radius.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A28
- Title:
- Halo metal-poor stars chemical data
- Short Name:
- J/A+A/593/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an analysis of 107 extremely metal-poor (EMP) stars with metallicities lower than [Fe/H]=-3.0, identified in medium-resolution spectra in the Sloan Digital Sky Survey (SDSS). Our analysis provides estimates of the stellar effective temperatures and surface gravities, as well as iron, calcium, and magnesium abundances. We followed the same method as in previous papers of this series. The method is based on comparisons of the observed spectra with synthetic spectra. The abundances of Fe, Ca, and Mg were determined by fitting spectral regions that are dominated by lines of each element. In addition, we present a technique to determine upper limits for elements whose features are not detected in a given spectrum. We also analyzed our sample with the SEGUE stellar parameter pipeline to obtain additional determinations of the atmospheric parameters and iron and alpha-element abundances, which we then compare with ours. In addition, we used these parameters to infer [C/Fe] ratios. Ca is typically the only element in these spectra with a moderate to low signal-to-noise ratio and medium resolution in this metallicity regime with lines that are sufficiently strong to reliably measure its abundance. Fe and Mg exhibit weaker features that in most cases only provide upper limits. We measured [Ca/Fe] and [Mg/Fe] for EMP stars in the SDSS spectra and conclude that most of the stars exhibit the typical enhancement level for alpha-elements, ~+0.4, although some stars for which only [Fe/H] upper limits could be estimated indicate higher [alpha/Fe] ratios. We also find that 26% of the stars in our sample can be classified as carbon-enhanced metal-poor (CEMP) stars and that the frequency of CEMP stars also increases with decreasing metallicity, as has been reported for previous samples. We identify a rare, bright (g=11.90) EMP star, SDSS J134144.61+474128.6, with [Fe/H]=-3.27, [C/Fe]=+0.95, and elevated magnesium ([Mg/Fe]=+0.62), an abundance pattern typical of CEMP-no stars.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A112
- Title:
- Halo oxygen-rich AGB stars catalog
- Short Name:
- J/A+A/626/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To construct a catalogue of oxygen-rich (M) asymptotic giant branch (AGB) stars in the halo, complementing the catalogues of carbon-rich (C) stars, previous lists of Miras and SRa semi-regulars located in the northern hemisphere are merged and cleaned of various defects. After putting aside known C stars, characteristics such as colours and periods indicate that most of the remaining objects are M stars. Distances are obtained through the period-luminosity relation. By considering their position in the sky, stars lying at |Z|>5kpc are confirmed to be in majority in the Sgr tidal arms. The M stars are more numerous than C ones. Our distance scale is supported by two cool variables located in the Pal 4 globular cluster. Along the Sgr arms, there is reasonable agreement on distances of our objects with recent RR Lyrae distances. A few stars may be as distant as 150kpc, with possibly four at the trailing arm apocentre, and two in the A16 sub-structure, angularly close to two C stars. Ninety radial velocities are collected from Gaia and other sources. A catalogue with 417 M pulsating AGB stars is provided. This catalogue contains about 260 stars in the halo with |Z|>5kpc. Their Ks magnitudes range from 8 up to 13. For comparison, the catalogue also provides about 150 stars in the disc having 5<Ks<8.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A136
- Title:
- Halo red giants from the SEGUE survey
- Short Name:
- J/A+A/534/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic search for halo field stars that originally formed in globular clusters. Using moderate-resolution SDSS-III/SEGUE-2 spectra of 561 red giants with typical halo metallicities (-1.8<=[Fe/H]<=-1.0), we identify 16 stars, 3% of the sample, with CN and CH bandstrength behavior indicating depleted carbon and enhanced nitrogen abundances relative to the rest of the data set. Since globular clusters are the only environment known in which stars form with this pattern of atypical light-element abundances, we claim that these stars are second-generation globular cluster stars that have been lost to the halo field via normal cluster mass-loss processes.
- ID:
- ivo://CDS.VizieR/J/AJ/107/1577
- Title:
- Halo red giants reddening
- Short Name:
- J/AJ/107/1577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Updated uvby observations for a larger sample of metal-deficient red giants are presented and combined with a select sample of data from the literature transformed to a common system. Using the reddening maps of Burstein & Heiles [AJ, 87, 1165 (1982)], new absolute magnitudes, distances, metallicities, and reddenings are derived for each star. The metallicities are determined with a revised calibration of the m1, (b-y) diagram based upon comparison to a compilation of recent spectroscopic abundances transformed to a common system. The photometric abundances agree very well with the spectroscopic; the dispersion among the residuals for 58 giants is +/-0.16dex. The dereddened indices are used to show that for red giants with [Fe/H]<-1.5, there is a well-defined relation in the c0, (b-y)0 diagram which exhibits only a weak dependence upon metallicity. Use of the standard relations allows one to obtain reddening estimates for normal halo field giants and globular clusters in the appropriate metallicity range.
7727. HaloSat Master Catalog
- ID:
- ivo://nasa.heasarc/halomaster
- Title:
- HaloSat Master Catalog
- Short Name:
- HALOMASTER
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table records high-level information for the observations obtained with HaloSat and provides access to the HaloSat data archive. HaloSat is the first astrophysics-focused CubeSat funded by NASA's Astrophysics Division (PI P. Kaaret, University of Iowa). HaloSat is designed to map soft X-ray oxygen line emissions across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. HaloSat was launched from the NASA Wallops Flight Facility and delivered to the International Space Station on May 21, 2018. HaloSat was deployed into orbit on July 13, 2018. The spacecraft and science instrument commissioning phase ended on October 16, 2018, and science operations started after that. Initially approved to operate for 12 months, HaloSat successfully collected science data from October 15, 2018, until September 29, 2020, effectively doubling the mission lifetime. HaloSat reentered Earth's atmosphere on January 4, 2021. To trace the Galactic halo, HaloSat is equipped with a non-focusing instrument, comprised of three independent silicon drift detectors (SDD14, SDD38, SDD54) operating in the energy range of 0.4 - 7.0 keV with a field of view of 10 deg in diameter and an energy resolution of 84.8 +/- 2.7 eV at 677 eV and 137.4 +/- 0.9 eV at 5895 eV. The observing strategy was to divide the sky into 333 positions (HaloSat fields) and acquire a minimum of 8000 detector-seconds for each position throughout the initial 12 months of operations. After launch, additional positions were added to the initial 333 positions. HaloSat observations of the chosen fields are divided in intervals of time such that the data files do not exceed 2GB. Each observation is labeled with a sequence number. This database table contains one record for each sequence number and includes parameters related to the observation. The contents of this database table are generated at the HEASARC using information from the data files. The table was last updated in April 2023. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/other/NatAs/4.1072
- Title:
- HaloSat survey of southern Galactic halo
- Short Name:
- J/other/NatAs/4.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity. The CGM may also be a repository for baryons seen in the early universe, but undetected locally. The CGM has an ionized component at temperatures near 2x10^6^K studied primarily in the soft X-ray band. Here we report a survey of the southern Galactic sky with a soft X-ray spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission is best fit with a disc-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of ~10 degrees indicate that the CGM is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/162
- Title:
- HaloSat targets to study the hot Galactic halo
- Short Name:
- J/ApJ/884/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HaloSat is a small satellite (CubeSat) designed to map soft X-ray oxygen line emission across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. The goal of HaloSat is to help determine if hot gas gravitationally bound to individual galaxies makes a significant contribution to the cosmological baryon budget. HaloSat was deployed from the International Space Station in 2018 July and began routine science operations in 2018 October. We describe the goals and design of the mission, the on-orbit performance of the science instrument, and initial observations.
7730. HaloSat Time Log
- ID:
- ivo://nasa.heasarc/halotimelg
- Title:
- HaloSat Time Log
- Short Name:
- HALOTIMELG
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table records the start and stop times of the uninterrupted observation intervals obtained by the three detectors on board of HaloSat and provides access to the HaloSat observations containing these intervals. HaloSat is the first astrophysics-focused CubeSat funded by NASA's Astrophysics Division (PI P. Kaaret, University of Iowa). HaloSat is designed to map soft X-ray oxygen line emissions across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. HaloSat was launched from the NASA Wallops Flight Facility and delivered to the International Space Station on May 21, 2018. HaloSat was deployed into orbit on July 13, 2018 and collected science data from October 15, 2018, until September 29, 2020. HaloSat reentered Earth's atmosphere on January 4, 2021. To trace the Galactic halo, HaloSat is equipped with a non-focusing instrument, comprised of three independent silicon drift detectors (SDD14, SDD38, SDD54) operating in the energy range of 0.4 - 7.0 keV with a field of view of 10 deg in diameter and an energy resolution of 84.8 +/- 2.7 eV at 677 eV and 137.4 +/- 0.9 eV at 5895 eV. The HaloSat data are divided by specific positions in the sky and labeled with a number, the sequence number. Each sequence number contains all data for a specific sky position collected during the HaloSat operations therefore each observation contains time intervals that may be apart day, week or months. This database table instead has in each record the start and stop times of one uninterrupted time interval of good data for a specific detector. This table therefore enables searches of the HaloSat data for a specific time event detected by different obsevatories. The contents of this database table are generated at the HEASARC using information from the data files. The table was created in April 2023. This is a service provided by NASA HEASARC .