- ID:
- ivo://CDS.VizieR/J/AJ/151/82
- Title:
- The 4 brightest red giants in the UFD galaxy Ret 2
- Short Name:
- J/AJ/151/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultra-faint dwarf (UFD) galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey (Diehl et al. 2014SPIE.9149E..0VD). We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present detailed abundances for as many as 20 elements per star, including 12 elements heavier than the Fe group. We confirm previous detection of high levels of r-process material in Ret 2 (mean [Eu/Fe]=+1.69+/-0.05) found in three of these stars (mean [Fe/H]=-2.88+/-0.10). The abundances closely match the r-process pattern found in the well-studied metal-poor halo star CS 22892-052. Such r-process-enhanced stars have not been found in any other UFD galaxy, though their existence has been predicted by at least one model. The fourth star in Ret 2 ([Fe/H]=-3.42+/-0.20) contains only trace amounts of Sr ([Sr/Fe]=-1.73+/-0.43) and no detectable heavier elements. One r-process enhanced star is also enhanced in C (natal [C/Fe]~+1.1). This is only the third such star known, which suggests that the nucleosynthesis sites leading to C and r-process enhancements are decoupled. The r-process-deficient star is enhanced in Mg ([Mg/Fe]=+0.81+/-0.14), and the other three stars show normal levels of {alpha}-enhancement (mean [Mg/Fe]=+0.34+/-0.03). The abundances of other {alpha} and Fe-group elements closely resemble those in UFD galaxies and metal-poor halo stars, suggesting that the nucleosynthesis that led to the large r-process enhancements either produced no light elements or produced light-element abundance signatures indistinguishable from normal supernovae.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/149/158
- Title:
- The BUD sample. I. L dwarf activity sample
- Short Name:
- J/AJ/149/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the colors and activity of ultracool (M7-L8) dwarfs from the Tenth Data Release of the Sloan Digital Sky Survey (SDSS). We combine previous samples of SDSS M and L dwarfs with new data obtained from the Baryon Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool Dwarf (BUD) sample of 11820 M7-L8 dwarfs. By combining SDSS data with photometry from 2MASS and the Wide-field Infrared Sky Explorer (WISE) mission, we present ultracool dwarf colors from i-z to W2-W3 as a function of spectral type, and extend the SDSS-2MASS-WISE color locus to include ultracool dwarfs. The i-z, i-J, and z-J colors provide the best indication of spectral type for M7-L3 dwarfs. We also examine ultracool dwarf chromospheric activity through the presence and strength of H{alpha} emission. The fraction of active dwarfs rises through the M spectral sequence until it reaches ~90% at spectral type L0. The fraction of active dwarfs then declines to 50% at spectral type L5; no H{alpha} emission is observed in the late-L dwarfs in the BUD sample. The fraction of active L0-L5 dwarfs is much higher than previously observed. The strength of activity declines with spectral type from M7 through L3, after which the data do not show a clear trend. Using one-dimensional chromosphere models, we explore the range of filling factors and chromospheric temperature structures that are consistent with H{alpha} observations of M0-L7 dwarfs. M dwarf chromospheres have a similar, smoothly varying range of temperature and surface coverage, while L dwarf chromospheres are cooler and have smaller filling factors.
- ID:
- ivo://CDS.VizieR/J/AJ/157/85
- Title:
- The CIDA Variability Survey of Orion OB1. II.
- Short Name:
- J/AJ/157/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of our large-scale, optical, multi-epoch photometric survey across ~180 square degrees in the Orion OB1 association, complemented with extensive follow-up spectroscopy. Our focus is mapping and characterizing the off-cloud, low-mass, pre-main-sequence (PMS) populations. We report 2062 K- and M-type confirmed T Tauri members; 59% are located in the OB1a subassociation, 27% in the OB1b subassociation, and the remaining 14% in the A and B molecular clouds. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both located in OB1a not far from the 25 Ori cluster. We also identify two stellar overdensities in OB1b, containing 231 PMS stars, and find that the OB1b region is composed of two populations at different distances, possibly due to the OB1a subassociation overlapping with the front of OB1b. A ~2 deg wide halo of young stars surrounds the Orion Nebula Cluster, corresponding in part to the low-mass populations of NGC 1977 and NGC 1980. We use the strength of H{alpha} in emission, combined with the IR excess and optical variability, to define a new type of T Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state between classical and weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of Li I{lambda}6707 indicates a Li depletion timescale of ~8.5 Myr. Disk accretion declines with an e-folding timescale of ~2 Myr, consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/ApJS/252/15
- Title:
- The GNRIS-Distant Quasar Survey (GNRIS-DQS)
- Short Name:
- J/ApJS/252/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic measurements for 226 sources from the Gemini Near Infrared Spectrograph-Distant Quasar Survey (GNIRS-DQS). Being the largest uniform, homogeneous survey of its kind, it represents a flux-limited sample (m_i_<~19.0mag, H<~16.5mag) of Sloan Digital Sky Survey (SDSS) quasars at 1.5<~z<~3.5 with a monochromatic luminosity ({lambda}L_{lambda}_) at 5100{AA} in the range of 10^44^-10^46^erg/s. A combination of the GNIRS and SDSS spectra covers principal quasar diagnostic features, chiefly the CIV{lambda}1549, MgII{lambda}{lambda}2798,2803, H{beta}{lambda}4861, and [OIII]{lambda}{lambda}4959,5007 emission lines, in each source. The spectral inventory will be utilized primarily to develop prescriptions for obtaining more accurate and precise redshifts, black hole masses, and accretion rates for all quasars. Additionally, the measurements will facilitate an understanding of the dependence of rest-frame ultraviolet-optical spectral properties of quasars on redshift, luminosity, and Eddington ratio, and test whether the physical properties of the quasar central engine evolve over cosmic time.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A36
- Title:
- The LickX Spectra library
- Short Name:
- J/A+A/561/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Collections of stellar spectra, often called stellar libraries, are useful in a variety of applications in the field of stellar populations. This is an attempt to improve the much-used Lick library of stellar spectra by removing jitter from the wavelength scale via cross-correlation, and calling the result the LickX library.
- ID:
- ivo://CDS.VizieR/J/A+AS/133/171
- Title:
- The Marseille Schmidt survey I.
- Short Name:
- J/A+AS/133/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present data from a moderately deep spectroscopic Schmidt survey (B_lim_=17.5) of "active galaxies" selected by the presence of emission lines in their spectra and/or their UV excess. 92 emission line objects have been found in two adjacent fields (approximately 50deg^2^) in the direction of the southern extension of the Virgo cluster. We give a catalog containing positions, photographic R and B magnitudes, U-R colors, effective diameters, redshifts, equivalent widths and intensity ratios of the [OIII]{lambda}{lambda}4959,5007, H{beta} and [OII]{lambda}3727 emission lines. On these fields, we evaluate the completeness limit of the survey at a pseudo B magnitude values of 15.7. A more elaborate astrophysical analysis will appear in a forthcoming paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/47
- Title:
- The MgII cross-section of red galaxies
- Short Name:
- J/ApJ/727/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a search for MgII(2796, 2803) absorption lines in Sloan Digital Sky Survey (SDSS) spectra of QSOs whose lines of sight pass within impact parameters {rho}~200kpc of galaxies with photometric redshifts of z=0.46-0.6 and errors {Delta}z~0.05. The galaxies selected have the same colors and luminosities as the Luminous Red Galaxy (LRG) population previously selected from the SDSS. A search for MgII lines within a redshift interval of +/-0.1 of a galaxy's photometric redshift shows that absorption by these galaxies is rare: the covering fraction is f({rho})~10%-15% between {rho}=20kpc and {rho}=100kpc, for MgII lines with rest equivalent widths of W_r_>=0.6{AA}, falling to zero at larger {rho}. There is no evidence that W_r_ correlates with impact parameter or galaxy luminosity.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/25
- Title:
- The most metal-poor stars in HES and SDSS. I.
- Short Name:
- J/ApJ/762/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 34 stars in the Hamburg/ESO Survey (HES) for metal-poor stars and the Sloan Digital Sky Survey (SDSS) that have [Fe/H]<~-3.0. Their median and minimum abundances are [Fe/H]=-3.1 and -4.1, respectively, while 10 stars have [Fe/H]<-3.5. High-resolution, high signal-to-noise spectroscopic data --equivalent widths and radial velocities-- are presented for these stars, together with an additional four objects previously reported or currently being investigated elsewhere. We have determined the atmospheric parameters, effective temperature (T_eff_), and surface gravity (logg), which are critical in the determination of the chemical abundances and the evolutionary status of these stars. Three techniques were used to derive these parameters. Spectrophotometric fits to model atmosphere fluxes were used to derive T_eff_, logg, and an estimate of E(B-V); H{alpha}, H{beta}, and H{gamma} profile fitting to model atmosphere results provided the second determination of T_eff_and logg; and finally, we used an empirical T_eff_-calibrated H{delta} index, for the third, independent T_eff_determination. The three values of T_eff_ are in good agreement, although the profile fitting may yield systematically cooler T_eff_values, by ~100K. This collective data set will be analyzed in future papers in the present series to utilize the most metal-poor stars as probes of conditions in the early universe.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/71
- Title:
- The [OIII] emission line in SDSS AGNs
- Short Name:
- J/ApJ/737/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use homogeneous samples of radio-quiet Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the connection between the velocity shift and the equivalent width (EW) of the [OIII]{lambda}5007 emission line, and their correlations with physical parameters of active galactic nuclei (AGNs). We find a significant and negative correlation between the EW of the core component, EW(core), and the blueshift of either the core (the peak), the wing, or the total profile of [OIII] emission; it is fairly strong for the blueshift of the total profile in particular. However, both quantities (EW and velocity shift) generally have only weak, if any, correlations with fundamental AGN parameters such as the nuclear continuum luminosity at 5100{AA} (L_5100_), black hole mass (M_BH_), and the Eddington ratio (L/L_Edd_); these correlations include the classical Baldwin effect of EW(core), an inverse Baldwin effect of EW(wing), and the relationship between velocity shifts and L/L_Edd_. Our findings suggest that both the large object-to-object variation in the strength of [OIII] emission and the blueshift-EW(core) connection are not governed primarily by fundamental AGN parameters such as L_5100_, M_BH_, and L/L_Edd_. We propose that the interstellar medium conditions of the host galaxies play a major role instead in the diversity of the [OIII] properties in active galaxies. This suggests that the use of [OIII]{lambda}5007 luminosity as a proxy of AGN luminosity does not depend strongly on the above-mentioned fundamental AGN parameters.
920. The Phoenix Survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/306/708
- Title:
- The Phoenix Survey
- Short Name:
- J/MNRAS/306/708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a deep Australia Telescope Compact Array (ATCA) radio survey covering an area of ~3deg^2^ to a 4{sigma} sensitivity of >=100mmJy at 1.4GHz, we study the nature of faint radio galaxies. About 50 per cent of the detected radio sources are identified with an optical counterpart revealed by CCD photometry to m_R=22.5mag. Near-infrared (K-band) data are also available for a selected sample of the radio sources, while spectroscopic observations have been carried out for about 40 per cent of the optically identified sample. These provide redshifts and information on the stellar content. Emission-line ratios imply that most of the emission-line sources are star-forming galaxies, with a small contribution (~10 per cent) from Sy1/Sy2 type objects. We also find a significant number of absorption-line systems, likely to be ellipticals. These dominate at high flux densities (>1mJy) but are also found at sub-mJy levels. Using the Balmer decrement we find a visual extinction A_V_=1.0 for the star-forming faint radio sources. This moderate reddening is consistent with the V-R and R-K colours of the optically identified sources. For emission-line galaxies, there is a correlation between the radio power and the Halpha luminosity, in agreement with the result of Benn et al. (1993MNRAS.263....9B). This suggests that the radio emission of starburst radio galaxies is a good indicator of star formation activity.
