- ID:
- ivo://CDS.VizieR/J/A+A/391/809
- Title:
- HII regions in NGC 5457 and NGC 4395
- Short Name:
- J/A+A/391/809
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Line intensities, visual extinction, abundances and ionization hardness parameter for HII regions in two spiral galaxies are presented. The following galaxies have been observed: NGC 5457 and NGC 4395. In NGC 5457 have been obtained data for 338 regions. In NGC 4395 have been obtained data for 158 regions. For each region position, visual extinction, H-alpha flux, H-alpha equivalent width, H-beta flux, H-beta equivalent width, [OII] flux, [OIII] flux, [SII] flux, [SIII] flux (only for NGC 5457), R23 parameter, oxygen abundance and ionization hardness parameter (only for NGC 5457) are given.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/830/13
- Title:
- Host-galaxy NUV-NIR data of 32 superluminous SNe
- Short Name:
- J/ApJ/830/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ultraviolet through near-infrared photometry and spectroscopy of the host galaxies of all superluminous supernovae (SLSNe) discovered by the Palomar Transient Factory prior to 2013 and derive measurements of their luminosities, star formation rates, stellar masses, and gas-phase metallicities. We find that Type I (hydrogen-poor) SLSNe (SLSNe I) are found almost exclusively in low-mass (M_*_<2x10^9^M_{sun}_) and metal-poor (12+log_10_[O/H]<8.4) galaxies. We compare the mass and metallicity distributions of our sample to nearby galaxy catalogs in detail and conclude that the rate of SLSNe I as a fraction of all SNe is heavily suppressed in galaxies with metallicities >~0.5Z_{sun}_. Extremely low metallicities are not required and indeed provide no further increase in the relative SLSN rate. Several SLSN I hosts are undergoing vigorous starbursts, but this may simply be a side effect of metallicity dependence: dwarf galaxies tend to have bursty star formation histories. Type II (hydrogen-rich) SLSNe (SLSNe II) are found over the entire range of galaxy masses and metallicities, and their integrated properties do not suggest a strong preference for (or against) low-mass/low-metallicity galaxies. Two hosts exhibit unusual properties: PTF 10uhf is an SLSN I in a massive, luminous infrared galaxy at redshift z=0.29, while PTF 10tpz is an SLSN II located in the nucleus of an early-type host at z=0.04.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/70
- Title:
- Hot subdwarf stars from Gaia DR2 and LAMOST DR5
- Short Name:
- J/ApJ/868/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 4593 hot subdwarf candidates from the Gaia DR2 Hertzsprung-Russell (HR) diagram. By combining the sample with Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we identified 294 hot subdwarf stars, including 169 sdB, 63 sdOB, 31 He-sdOB, 22 sdO, 7 He-sdO, and 2 He-sdB stars. The atmospheric parameters (e.g., Teff, logg, log(nHe/nH)) are obtained by fitting the hydrogen (H) and helium (He) line profiles with synthetic spectra. Two distinct He sequences of hot subdwarf stars are clearly presented in the Teff-logg diagram. We found that the He-rich sequence consists of the bulk of sdB and sdOB stars, as well as all of the He-sdB, He-sdO, and He-sdOB stars in our samples, while all the stars in the He-weak sequence belong to the sdO spectral type, combined with a few sdB and sdOB stars. We demonstrated that the combination of Gaia DR2 and LAMOST DR5 allows one to uncover a huge number of new hot subdwarf stars in our Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A25
- Title:
- HST WFC3 photometry of NGC 2419
- Short Name:
- J/A+A/624/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W-F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of {Delta}Y~=0.05, but the P2 stars exhibit a significant spread in He content and some may reach {Delta}Y~=0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances ([Mg/Fe]<0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p~=0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/39
- Title:
- Hydra I wide-field imaging and spectroscopy obs.
- Short Name:
- J/ApJ/818/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d~10kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (~5-6Gyr) and metallicity ([Fe/H]=-0.9dex). We measure statistically significant spreads in both the iron and alpha-element abundances of {sigma}_[Fe/H]_=0.13+/-0.02dex and {sigma}_[{alpha}/Fe]_=0.09+/-0.03dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H] --as well as its low [{alpha}/Fe], apparent [Fe/H] spread, and present-day low luminosity-- suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/158/105
- Title:
- IR photometry of field RR Lyrae variable stars
- Short Name:
- J/AJ/158/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch infrared photometry in the K_s_-band for 74 bright RR Lyrae variable stars tied directly to the Two-Micron All-Sky Survey (2MASS) photometric system. We systematize additional K-band photometry from the literature to the 2MASS system and combine it to obtain photometry for 146 RR Lyrae stars on a consistent, modern system. A set of outlier stars in the literature photometry is identified and discussed. Reddening estimates for each star are gathered from the literature and combined to provide an estimate of the interstellar absorption affecting each star, and we find excellent agreement with another source in the literature. We utilize trigonometric parallaxes from the Second Data Release of the European Space Agency's Gaia astrometric satellite to determine the absolute magnitude, M_Ks_ for each of these stars, and analyze them using the astrometry-based luminosity prescription to obtain a parallax-based calibration of M_K_ (RR). Our period-luminosity-metallicity relationship is M_Ks_=(-2.8+/-0.2)(logP+0.27)+(0.12+/-0.02) ([Fe/H]+1.3)-(0.41+/-0.03) mag. A Gaia global zero-point error of {pi}_zp_=-0.042+/-0.013 mas is determined for this sample of RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/102
- Title:
- KIC star parallaxes from asteroseismology vs Gaia
- Short Name:
- J/ApJ/844/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of parallaxes and radii from asteroseismology and Gaia DR1 (TGAS) for 2200 Kepler stars spanning from the main sequence to the red-giant branch. We show that previously identified offsets between TGAS parallaxes and distances derived from asteroseismology and eclipsing binaries have likely been overestimated for parallaxes <~5-10mas (~90%-98% of the TGAS sample). The observed differences in our sample can furthermore be partially compensated by adopting a hotter Teff scale (such as the infrared flux method) instead of spectroscopic temperatures for dwarfs and subgiants. Residual systematic differences are at the ~2% level in parallax across three orders of magnitude. We use TGAS parallaxes to empirically demonstrate that asteroseismic radii are accurate to ~5% or better for stars between ~0.8-8R_{sun}_. We find no significant offset for main- sequence (<~1.5R_{sun}_) and low-luminosity RGB stars (~3-8R_{sun}_), but seismic radii appear to be systematically underestimated by ~5% for subgiants (~1.5-3R_{sun}_). We find no systematic errors as a function of metallicity between [Fe/H]~-0.8 to +0.4dex, and show tentative evidence that corrections to the scaling relation for the large frequency separation ({Delta}{nu}) improve the agreement with TGAS for RGB stars. Finally, we demonstrate that beyond ~3kpc asteroseismology will provide more precise distances than end-of-mission Gaia data, highlighting the synergy and complementary nature of Gaia and asteroseismology for studying galactic stellar populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/172
- Title:
- Kinematic analysis of red giant in M31 dSphs
- Short Name:
- J/ApJ/768/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g-i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii (>~700pc) and low velocity dispersions ({sigma}_v_<5km/s). In addition, And XXV has a mass-to-light ratio within its half-light radius of just [M/L]_half_=10.3_-6.7_^7.0^, making it consistent with a simple stellar system with no appreciable dark matter component within its 1{sigma} uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/202
- Title:
- Kinematic study of the Leo II dwarf galaxy
- Short Name:
- J/ApJ/836/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a large spectroscopic survey of 336 red giants in the direction of the Leo II dwarf galaxy using Hectochelle on the Multiple Mirror Telescope, and we conclude that 175 of them are members based on their radial velocities and surface gravities. Of this set, 40 stars have never before been observed spectroscopically. The systemic velocity of the dwarf is 78.3+/-0.6km/s with a velocity dispersion of 7.4+/-0.4km/s. We identify one star beyond the tidal radius of Leo II but find no signatures of uniform rotation, kinematic asymmetries, or streams. The stars show a strong metallicity gradient of -1.53+/-0.10dex/kpc and have a mean metallicity of -1.70+/-0.02dex.
- ID:
- ivo://CDS.VizieR/J/ApJS/222/19
- Title:
- KPNO spectroscopy of G & K dwarfs HIP stars
- Short Name:
- J/ApJS/222/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tension between the Hipparcos parallax of the Pleiades and other independent distance estimates continues even after the new reduction of the Hipparcos astrometric data and the development of a new geometric distance measurement for the cluster. A short Pleiades distance from the Hipparcos parallax predicts a number of stars in the solar neighborhood that are sub-luminous at a given photospheric abundance. We test this hypothesis using the spectroscopic abundances for a subset of stars in the Hipparcos catalog, which occupy the same region as the Pleiades in the color-magnitude diagram. We derive stellar parameters for 170 nearby G- and K-type field dwarfs in the Hipparcos catalog based on high-resolution spectra obtained using KPNO 4m echelle spectrograph. Our analysis shows that, when the Hipparcos parallaxes are adopted, most of our sample stars follow empirical color-magnitude relations. A small fraction of stars are too faint compared to main-sequence fitting relations by {Delta}M_V_>~0.3mag, but the differences are marginal at a 2{sigma} level, partly due to relatively large parallax errors. On the other hand, we find that the photometric distances of stars showing signatures of youth as determined from lithium absorption line strengths and R'_HK_ chromospheric activity indices are consistent with the Hipparcos parallaxes. Our result is contradictory to a suggestion that the Pleiades distance from main-sequence fitting is significantly altered by stellar activity and/or the young age of its stars, and provides an additional supporting evidence for the long-distance scale of the Pleiades.