- ID:
- ivo://CDS.VizieR/J/ApJ/765/137
- Title:
- HST survey for Lyman limit systems. II.
- Short Name:
- J/ApJ/765/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first science results from our Hubble Space Telescope survey for Lyman limit absorption systems (LLS) using the low dispersion spectroscopic modes of the Advanced Camera for Surveys and the Wide Field Camera 3. Through an analysis of 71 quasars, we determine the incidence frequency of LLS per unit redshift and per unit path length, l(z) and l(X), respectively, over the redshift range 1<z<2.6, and find a weighted mean of l(X)=0.29+/-0.05 for 2.0<z<2.5 through a joint analysis of our sample and that of Ribaudo et al. (2011, J/ApJ/736/42). Through stacked spectrum analysis, we determine a median (mean) value of the mean free path to ionizing radiation at z=2.4 of {lambda}^912^_mfp_=243(252)h^-1^_72_Mpc, with an error on the mean value of +/-43h^-1^_72_Mpc. We also re-evaluate the estimates of {lambda}^912^_mfp_ from Prochaska et al. (2010, J/ApJ/718/392) and place constraints on the evolution of {lambda}^912^_mfp_ with redshift, including an estimate of the "breakthrough" redshift of z=1.6. Consistent with results at higher z, we find that a significant fraction of the opacity for absorption of ionizing photons comes from systems with N_HI_<=10^17.5^cm^-2^ with a value for the total Lyman opacity of {tau}^Lyman^_eff_=0.40+/-0.15. Finally, we determine that at minimum, a 5-parameter (4 power law) model is needed to describe the column density distribution function f(N_HI_,X) at z~2.4, find that f(N_HI_,X) undergoes no significant change in shape between z~2.4 and z~3.7, and provide our best fit model for f(N_HI_,X).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/297/617
- Title:
- Hydra/Antlia extension redshifts
- Short Name:
- J/A+A/297/617
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations have been carried out for galaxies in the Milky Way with the 1.9m telescope of the South African Astronomical Observatory (SAAO). The galaxies were selected from a deep optical galaxy search covering 266deg<~l<~296deg, |b|<~10deg (Kraan-Korteweg 1994). This is in the extension of the Hydra and Antlia clusters and in the approximate direction of the dipole anisotropy in the Cosmic Microwave Background radiation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2332
- Title:
- Hydrogen Lyman and Balmer line profiles
- Short Name:
- J/MNRAS/448/2332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new calculations of unified line profiles for hydrogen perturbed by collisions with protons. We report on new calculations of the potential energies and dipole moments which allow the evaluation of profiles for the lines of the Lyman series up to Lyman {delta} and the Balmer series up to Balmer 10. Unified calculations only existed for the lines Lyman {alpha} to Lyman {gamma} and Balmer {alpha} including the H_2_^+^ quasi-molecule. These data are available as online material accompanying this paper and should be included in atmosphere models, in place of the Stark effect of protons, since the quasi-molecular contributions cause not only satellites, but large asymmetries that are unaccounted for in models that assume that Stark broadening of electrons and that of protons are equal.
234. IC 4665
- ID:
- ivo://CDS.VizieR/J/AJ/105/1441
- Title:
- IC 4665
- Short Name:
- J/AJ/105/1441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665's age using different methods yields conflicting results ranging from approx. 3x10^7^ yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members. The results of new echelle observations of some candidates and the photometric monitoring of one apparent cluster member are given in an appendix.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/26
- Title:
- Identifying 3FHL. V. CTIO-COSMOS spectra
- Short Name:
- J/ApJS/254/26
- Date:
- 19 Jan 2022 00:35:09
- Publisher:
- CDS
- Description:
- As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A65
- Title:
- IFU observations of NGC 4191
- Short Name:
- J/A+A/581/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We here distinguish two counter-rotating stellar components in NGC 4191 and characterize their physical properties such as kinematics, size, morphology, age, metallicity. We obtained integral field spectroscopic observations with VIRUS-W and used a spectroscopic decomposition technique to separate the contribution of two stellar components to the observed galaxy spectrum. We also performed a photometric decomposition, modeling the galaxy with a Sersic bulge and two exponential disks of different scale length, with the aim of associating these structural components with the kinematic components. We then measured the equivalent width of the absorption line indices on the best-fit models that represent the kinematic components and compared our measurements to the predictions of stellar population models that also account for the variable abundance ratio of {alpha} elements.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A157
- Title:
- 5 ILRTs light curves and spectra
- Short Name:
- J/A+A/654/A157
- Date:
- 07 Mar 2022 07:10:34
- Publisher:
- CDS
- Description:
- We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between -11:5 and -14:5mag. Their pseudo-bolometric light curves peak in the range 0.5-9.0*10^40^erg/s and their total radiated energies are on the order of (0.3-3)*10^47^erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the ^56^Co decay. If the late-time power source is indeed radioactive decay, these transients produce ^56^Ni masses on the order of 10^-4^ to 10^-3^M_{sun}_. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km/s, along with CaII features. In particular, the [CaII]7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.
- ID:
- ivo://CDS.VizieR/J/AJ/145/77
- Title:
- Imaging and spectroscopy in three galaxy clusters
- Short Name:
- J/AJ/145/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6-0305 (z=0.54), RXJ0152.7-1357 (z=0.83), and RXJ1226.9+3332 (z=0.89). Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster. Using the dynamical masses together with the effective radii and the velocity dispersions, we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices and velocity dispersions. We confirm that the FP is steeper at z~0.86 compared to the low-redshift FP, indicating that under the assumption of passive evolution the formation redshift, z_form_, depends on the galaxy velocity dispersion (or alternatively mass). At a velocity dispersion of {sigma}=125km/s (Mass=10^10.55^M_{sun}_) we find z_form_=1.24+/-0.05, while at {sigma}=225km/s (Mass=10^11.36^M_{sun}_) the formation redshift is z_form_=1.95^+0.3^_-0.2_, for a Salpeter initial mass function. The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low-redshift galaxies. The zero point offsets for the Balmer lines depend on cluster redshifts. However, the offsets indicate a slower evolution, and therefore higher formation redshift, than the zero point differences found from the FP, if interpreting the data using a passive evolution model. Specifically, the strength of the higher order Balmer lines H{delta} and H{gamma} implies z_form_>2.8. The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets, favoring high formation redshifts for a passive evolution model.
- ID:
- ivo://CDS.VizieR/J/ApJ/845/157
- Title:
- IMF in 3 low-redshift strong lenses from SNELLS
- Short Name:
- J/ApJ/845/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of the three nearest early-type galaxy (ETG) strong lenses discovered in the SINFONI Nearby Elliptical Lens Locator Survey (SNELLS). Based on their lensing masses, these ETGs were inferred to have a stellar initial mass function (IMF) consistent with that of the Milky Way, not the bottom-heavy IMF that has been reported as typical for high-{sigma} ETGs based on lensing, dynamical, and stellar population synthesis techniques. We use these unique systems to test the consistency of IMF estimates derived from different methods. We first estimate the stellar M*/L using lensing and stellar dynamics. We then fit high-quality optical spectra of the lenses using an updated version of the stellar population synthesis models developed by Conroy & van Dokkum. When examined individually, we find good agreement among these methods for one galaxy. The other two galaxies show 2-3{sigma} tension with lensing estimates, depending on the dark matter contribution, when considering IMFs that extend to 0.08M_{sun}_. Allowing a variable low-mass cutoff or a nonparametric form of the IMF reduces the tension among the IMF estimates to <2{sigma}. There is moderate evidence for a reduced number of low-mass stars in the SNELLS spectra, but no such evidence in a composite spectrum of matched-{sigma} ETGs drawn from the SDSS. Such variation in the form of the IMF at low stellar masses (m<~0.3M_{sun}_), if present, could reconcile lensing/dynamical and spectroscopic IMF estimates for the SNELLS lenses and account for their lighter M*/L relative to the mean matched-{sigma} ETG. We provide the spectra used in this study to facilitate future comparisons.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A102
- Title:
- Inner/outer HII regions: galaxy sample
- Short Name:
- J/A+A/609/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer HII regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. We find that inner HII regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [NII] {lambda}6583/H{alpha} and [OII] {lambda}3727/[OIII] {lambda}5007 emission-line ratios, indicating higher metallicities and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although Mion/Mphot is slightly higher for the outer regions. This work shows important observational differences between inner and outer HII regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm.
