- ID:
- ivo://CDS.VizieR/J/ApJ/543/552
- Title:
- z>3 damped Ly{alpha} absorption systems
- Short Name:
- J/ApJ/543/552
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have completed spectroscopic observations using LRIS on the Keck 1 telescope of 30 very high redshift quasars, 11 selected for the presence of damped Ly{alpha} absorption systems and 19 with redshifts z>3.5 not previously surveyed for absorption systems. We have surveyed an additional 10 QSOs with the Lick 120" and the Anglo-Australian Telescope. We have combined these with previous data, resulting in a statistical sample of 646 QSOs and 85 damped Ly{alpha} absorbers with column densities N_HI_>=2 10^20^atoms/cm^2^ covering the redshift range 0.008<=z<=4.694. Four main features of how the neutral gas in the universe evolves with redshift are evident from these data.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/656/A94
- Title:
- Z-dependent yields of double detonations
- Short Name:
- J/A+A/656/A94
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Double detonations in sub-Chandrasekhar mass carbon-oxygen white dwarfs with helium shell are a potential explosion mechanism for a Type Ia supernova. It comprises a shell detonation and subsequent core detonation. The focus of our study is on the effect of the progenitor metallicity on the nucleosynthetic yields. For this, we compute and analyse a set of eleven different models with varying core and shell masses at four different metallicities each. This results in a total of 44 models at metallicities between 0.01Z_{sun}_ and 3Z_{sun}_. Our models show a strong impact of the metallicity in the high density regime. The presence of ^22^$Ne causes a neutron-excess which shifts the production from ^56^Ni to stable isotopes such as ^54^Fe and ^58^Ni in the {alpha}-rich freeze-out regime. The isotopes of the metallicity implementation further serve as seed nuclei for additional reactions in the shell detonation. Most significantly, the production of ^55^Mn increases with metallicity confirming the results of previous work. A comparison of elemental ratios relative to iron shows a relatively good match to solar values for some models. Super-solar values are reached for Mn at 3Z_{sun}_ and solar values in some models at Z_{sun}_. This indicates that the required contribution of Type Ia supernovae originating from Chandrasekhar mass WDs can be lower than estimated in previous work to reach solar values of [Mn/Fe] at [Fe/H]=0. Our galactic chemical evolution models suggest that Type Ia supernovae from sub-Chandrasekhar mass white dwarfs, along with core-collapse supernovae, could account for more than 80% of the solar Mn abundance. Using metallicity-dependent Type Ia supernova yields helps to reproduce the upward trend of [Mn/Fe] as a function of metallicity for the solar neighborhood. These chemical evolution predictions, however, depend on the massive star yields adopted in the calculations.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A71
- Title:
- ZDI maps of five young solar-type stars
- Short Name:
- J/A+A/659/A71
- Date:
- 09 Mar 2022 16:47:36
- Publisher:
- CDS
- Description:
- The magnetic activity of the Sun changes with the solar cycle. Similar cycles are found in other stars as well, but their details are not known to a similar degree. Characterising stellar magnetic cycles is important for the understanding of the stellar and solar dynamos that are driving the magnetic activity. We present spectropolarimetric observations of five young, solar-type stars and compare them to previous observations, with the aim to identify and characterise stellar equivalents of the solar cycle. We use Zeeman-Doppler imaging (ZDI) to map the surface magnetic field and brightness of our targets. The magnetic field is decomposed into spherical harmonic expansions, from which we report the strengths of the axisymmetric versus non-axisymmetric and poloidal versus toroidal components, and we compare them to the Rossby numbers of the stars. We present five new ZDI maps of young, solar-type stars from December 2017. Of special interest is the case of V1358 Ori, which had gone through a polarity reversal between our observations and earlier ones. A less evident polarity reversal might also have occurred in HD 35296. There is a preference for a more axisymmetric field, and possibly a more toroidal field, for the more active stars with lower Rossby number, but a larger sample should be studied to draw any strong conclusions from this. For most of the individual stars, the amounts of toroidal and poloidal field have stayed on levels similar to those in earlier observations. We find evidence for a magnetic polarity reversal having occurred in V1358 Ori. An interesting target for future observations is {chi}^1^ Ori, which may have a short magnetic cycle of a few years. The correlation between the brightness maps and the magnetic field is mostly poor, which could indicate the presence of small-scale magnetic features of different polarities that cancel one another out and are thus not resolved in our maps.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A20
- Title:
- Zeeman effect in sulfur monoxide (SO)
- Short Name:
- J/A+A/605/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN. We decided to investigate the suitability of sulfur monoxide (SO), which is one of the most abundant species in star forming regions, for probing the intensity of magnetic fields via the Zeeman effect. We investigated the Zeeman effect for several rotational transitions of SO in the (sub-)mm spectral regions by using a frequency-modulated, computer-controlled spectrometer, and by applying a magnetic field parallel to the radiation propagation (i.e., perpendicular to the oscillating magnetic field of the radiation). To support the experimental determination of the g factors of SO, a systematic quantum-chemical investigation of these parameters for both SO and O_2_ has been carried out.
- ID:
- ivo://CDS.VizieR/J/other/BSAO/45.136
- Title:
- Zelenchuk survey 9h<=RA<=12h, 0<=DE<=8{deg}
- Short Name:
- J/other/BSAO/45.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical identification of Zelenchuk Survey radio sources at 3.9GHz from 9h to 12h in right ascension and between 0{deg} and 8{deg} in declination is reported in this paper. Some optical characteristics of identified radio sources are presented in the table.
- ID:
- ivo://CDS.VizieR/J/ApJ/776/71
- Title:
- ZENS: galaxies in groups along the cosmic web. I.
- Short Name:
- J/ApJ/776/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Zurich Environmental Study (ZENS) is based on a sample of ~1500 galaxy members of 141 groups in the mass range ~10^12.5-14.5^M_{sun}_ within the narrow redshift range 0.05<z<0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ~40% of <10^13.5^M_{sun}_ groups, from which we estimate that ~15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ~30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M>10^10^M_{sun}_, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1919
- Title:
- Zero point spectral energy distribution
- Short Name:
- J/AJ/140/1919
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The absolutely calibrated infrared (IR) stellar spectra of standard stars described by Engelke et al. are being extended into the visible and will span a continuous wavelength range from ~0.35um to 35.0um. This paper, which is a continuation of the series on calibration initiated with Cohen et al., presents the foundation of this extension. We find that due to various irregularities Vega ({alpha} Lyr) is not suitable for its traditional role as the primary visible or near-infrared standard star. We therefore define a new zero-point flux that is independent of Vega and, as far as is feasible, uses measured spectral energy distributions (SEDs) and fluxes derived from photometry. The calibrated primary stars now underpinning this zero-point definition are 109 Vir in the visible and Sirius ({alpha} CMa) in the infrared. The resulting zero-point SED tests well against solar analog data presented by Rieke et al. (2008, Cat. J/AJ/135/2245) while also maintaining an unambiguous link to specific calibration stars, thus providing a pragmatic range of options for any researcher wishing to tie it to a given set of photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/645/L6
- Title:
- zet01 Ret and zet02 activity indexes
- Short Name:
- J/A+A/645/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore if the star zet02 Ret, which belongs to a binary system, is in (or going to) a state similar to the MM. To do so, we have collected more than 430 spectra acquired between 2000 and 2019 with the HARPS, REOSC, UVES, and FEROS spectrographs. We performed a detailed long-term activity study of both components using the Mount Wilson index, which is obtained from the Ca II H&K lines. To search for signs of an activity cycle, we analyzed the resulting time-series with the Generalized Lomb-Scargle and CLEAN periodograms. Our spectroscopic analysis shows a high activity level for zet01 Ret and a significant decrease in the magnetic activity cycle amplitude of zet02 Ret. By analogy with the scenario that proposes a weak solar cycle during the MM, we suggest that activity signatures showed by zet02 Ret, i.e., a very low activity level when compared to its stellar companion, a notably decreasing amplitude (~47%), and a cyclic behaviour, are possible evidence that this star could be in a MM state. It is, to our knowledge, the first MM candidate star detected through a highly discrepant activity behaviour in a binary system.
25509. ZFIRE v1.0 data release
- ID:
- ivo://CDS.VizieR/J/ApJ/828/21
- Title:
- ZFIRE v1.0 data release
- Short Name:
- J/ApJ/828/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties in rich environments at 1.5<z<2.5. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infrared imaging (K_AB_<25) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013 and 2015, ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over 1.57<z<2.66 from a combination of nebular emission lines (such as H{alpha}, [NII], H{beta}, [OII], [OIII], and [SII]) observed at 1-2{mu}m. Based on our medium-band near infrared photometry, we are able to spectrophotometrically flux calibrate our spectra to ~10% accuracy. ZFIRE reaches 5{sigma} emission line flux limits of ~3x10^-18^erg/s/cm^2^ with a resolving power of R=3500 and reaches masses down to ~10^9^M_{sun}_. We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to {Delta}z/(1+z_spec_)=0.015 with 0.7% outliers. We measure a slight redshift bias of <0.001, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colors and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically confirmed z~2 samples across a richer range of environments, here we make available the first public release of the data for use by the community.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/629
- Title:
- ZFOURGE catalogue of AGN candidates
- Short Name:
- J/MNRAS/457/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep Ks-band imaging of ZFOURGE with overlapping multiwavelength data. From this, we construct a mass-complete (log(M*/M_{sun}_)>=9.75), AGN luminosity limited sample of 235 AGN hosts over z=0.2-3.2. We compare the rest-frame U-V versus V-J (UVJ) colours and specific star formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160{mu}m Herschel PACS data, we find the mean specific star formation rate of AGN hosts to be elevated by 0.34-/-0.07dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ~5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested.