- ID:
- ivo://CDS.VizieR/J/ApJ/833/283
- Title:
- HI-selected Lyman limit systems metallicities
- Short Name:
- J/ApJ/833/283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our KODIAQ Z survey aimed at determining the metallicity distribution and physical properties of the z>~2 partial and full Lyman limit systems (pLLSs and LLSs; 16.2<=logN_HI_<19), which are probed of the interface regions between the intergalactic medium (IGM) and galaxies. We study 31 HI-selected pLLSs and LLSs at 2.3<z<3.3 observed with Keck/HIRES in absorption against background QSOs. We compare the column densities of metal ions to HI and use photoionization models to assess the metallicity. The metallicity distribution of the pLLSs/LLSs at 2.3<z<3.3 is consistent with a unimodal distribution peaking at [X/H]~-2. The metallicity distribution of these absorbers therefore evolves markedly with z since at z<~1 it is bimodal with peaks at [X/H]~-1.8 and -0.3. There is a substantial fraction (25%-41%) of pLLSs/LLSs with metallicities well below those of damped Ly{alpha} absorbers (DLAs) at any studied z from z<~1 to z~2-4, implying reservoirs of metal-poor, cool, dense gas in the IGM/galaxy interface at all z. However, the gas probed by pLLSs and LLSs is rarely pristine, with a fraction of 3%-18% for pLLSs/LLSs with [X/H]<=-3. We find C/{alpha} enhancement in several pLLSs and LLSs in the metallicity range -2<~[X/H]<~-0.5, where C/{alpha} is 2-5 times larger than observed in Galactic metal-poor stars or high-redshift DLAs at similar metallicities. This is likely caused by preferential ejection of carbon from metal-poor galaxies into their surroundings.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/VIII/77
- Title:
- HI spectral properties of galaxies
- Short Name:
- VIII/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous compilation of HI spectral parameters extracted from global 21cm line spectra for some 9000 galaxies in the local universe (heliocentric velocity -200<V_{sun}_<28,000km/s) obtained with a variety of large single-dish radio telescopes but reanalyzed using a single set of parameter extraction algorithms. Corrections to the observed HI line flux for source extent and pointing offsets and to the HI line widths for instrumental broadening and smoothing are applied according to model estimates to produce a homogenous catalog of derived properties with quantitative error estimates. Where the redshift is available from optical studies, we also provide flux measurements for an additional 156 galaxies classified as marginal HI detections and rms noise limits for 494 galaxies classified as nondetections.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A18
- Title:
- HI spectra of extremely metal-poor (XMP) galaxies
- Short Name:
- J/A+A/558/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extremely metal-poor (XMP) galaxies are chemically, and possibly dynamically, primordial objects in the local Universe. Our objective is to characterize the HI content of the XMP galaxies as a class, using as a reference the list of 140 known local XMPs compiled by Morales-Luis et al. (2011, Cat. J/ApJ/743/77). We have observed 29 XMPs, which had not been observed before at 21 cm, using the Effelsberg radio telescope. This information was complemented with Hi data published in literature for a further 53 XMPs. In addition, optical data from the literature provided morphologies, stellar masses, star-formation rates and metallicities.
1084. HI survey of AGNs
- ID:
- ivo://CDS.VizieR/J/ApJS/177/103
- Title:
- HI survey of AGNs
- Short Name:
- J/ApJS/177/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a new Arecibo survey for HI emission for 113 galaxies with broad-line (type 1) active galactic nuclei (AGNs) out to recession velocities as high as ~35000km/s. The primary aim of the study is to obtain sensitive HI spectra for a well-defined, uniformly selected sample of active galaxies that have estimates of their black hole masses in order to investigate correlations between HI properties and the characteristics of the AGNs. HI emission was detected in 66 out of the 101 (65%) objects with spectra uncorrupted by radio frequency interference, among which 45 (68%) have line profiles with adequate signal-to-noise ratio and sufficiently reliable inclination corrections to yield robust deprojected rotational velocities. This paper presents the basic survey products, including an atlas of HI spectra, measurements of HI flux, line width, profile asymmetry, optical images, optical spectroscopic parameters, as well as a summary of a number of derived properties pertaining to the host galaxies. To enlarge our primary sample, we also assemble all previously published HI measurements of type 1 AGNs for which we can estimate black hole masses, which total an additional 53 objects. The final comprehensive compilation of 154 broad-line active galaxies, by far the largest sample ever studied, forms the basis of our companion paper, which uses the HI database to explore a number of properties of the AGN host galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/99
- Title:
- HK', CN & CH chemical indexes in NGC 362 & NGC 6723
- Short Name:
- J/ApJ/832/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most globular clusters (GCs) are now known to host multiple stellar populations with different abundances of light elements. Here we use narrow-band photometry and low-resolution spectroscopy for NGC 362 and NGC 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC 362 and NGC 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN-CH anticorrelation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak, earlier generation stars compared to the CN-strong, later generation stars. These trends are reversed with respect to those found in previous studies for many other GCs. Our findings, therefore, seem contradictory to the current scenario for the formation of multiple stellar populations, but mass segregation acting on the two subpopulations might be a possible solution to explain this reversed radial trend.
1086. HLock01-LAB 2D spectrum
- ID:
- ivo://CDS.VizieR/J/A+A/629/A23
- Title:
- HLock01-LAB 2D spectrum
- Short Name:
- J/A+A/629/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of HLock01-LAB, a luminous and large Ly{alpha} nebula at z=3.326. Medium-band imaging and long-slit spectroscopic observations with the Gran Telescopio Canarias reveal extended emission in the Ly{alpha} 1215{AA}, CIV 1550{AA}, and HeII 1640{AA} lines over ~100kpc, and a total luminosity L(Ly{alpha})=(6.4+/-0.1)x10^44^erg/s. HLock01-LAB presents an elongated morphology aligned with two faint radio sources contained within the central ~8kpc of the nebula. The radio structures are consistent with faint radio jets or lobes of a central galaxy, whose spectrum shows nebular emission characteristic of a type-II active galactic nucleus (AGN). The continuum emission of the AGN at short wavelengths is however likely dominated by stellar emission of the host galaxy, for which we derive a stellar mass M*~2.3x10^11^M_{sun}_. Our kinematic analysis shows that the ionized gas is perturbed almost exclusively in the inner region between the radio structures, probably as a consequence of jet-gas interactions, whereas in the outer regions the ionized gas appears more quiescent. The detection of extended emission in CIV and CIII] indicates that the gas within the nebula is not primordial. Feedback may have enriched the halo at at least 50kpc from the nuclear region. Using rest-frame UV emission-line diagnostics, we find that the gas in the nebula is likely heated by the AGN. Nevertheless, at the center of the nebula we find extreme emission line ratios of Ly{alpha}/CIV~60 and Ly{alpha}/HeII~80, one of the highest values measured to date, and well above the standard values of photoionization models (Ly{alpha}/HeII ~30 for case B photoionization). Our data suggest that jet-induced shocks are likely responsible for the increase of the electron temperature and, thus, the observed Ly{alpha} enhancement in the center of the nebula. This scenario is further supported by the presence of radio structures and perturbed kinematics in this region. The large Ly{alpha} luminosity in HLock01-LAB is likely due to a combination of AGN photoionization and jet-induced shocks, highlighting the diversity of sources of energy powering Ly{alpha} nebulae. Future follow-up observations of HLock01-LAB will help to reveal the finer details of the excitation conditions of the gas induced by jets and to investigate the underlying cooling and feedback processes in this unique object.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A150
- Title:
- HNCO in planetary atmospheres.
- Short Name:
- J/A+A/616/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-resolved Fourier transform infrared emission spectroscopy, Fourier transform absorption infrared spectroscopy, and high-resolution UV-ViS emission spectroscopy have been exploited in order to characterize the chemistry of isocyanic acid (HNCO) under glow discharge conditions in planetary atmospheres. HNCO mixtures (i.e., composed of di-hydrogen or ammonia) have been investigated in order to unveil the possible reaction pathways leading to the synthesis of the key prebiotic molecule formamide (HCONH_2_), upon planetary atmospheres containing isocyanic acid in presence of di-hydrogen and, separately, of ammonia. In addition, ab initio Molecular Dynamics simulations coupled with a state-of-the-art metadynamics technique have been performed in order to identify the most likely chemical pathways connecting HNCO to formamide. It turned out that the direct hydrogenation of HNCO is thermodynamically favored. Incidentally, also the experimental results - supplied by a simplified kinetic model - proved the favorability of the reaction HNCO + H_2_ -> HCONH_2_ which, moreover, spontaneously takes place in unbiased ab initio Molecular Dynamics simulations carried out under the effect of intense electric fields.
- ID:
- ivo://CDS.VizieR/J/A+A/391/967
- Title:
- H2O and SiO masers in the Galactic center
- Short Name:
- J/A+A/391/967
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed targeted surveys for 22GHz H_2_O and 43GHz SiO maser emission in Galactic center OH/IR stars using the Very Large Array. Some of the detections have been used in a previous paper to investigate the possibility of measuring milli-arcsecond accurate positions (to obtain stellar proper motions) in the Galactic center. Here we report on the detection of at least 25 H_2_O masers and 18 SiO masers associated with stars within 2{deg} and 15' of Sgr A*, respectively. This survey has more than doubled the total number of proper motion candidates to at least about 50 stellar objects.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A80
- Title:
- H_2_O lines reduced spectra in 11 ULIRGs or HyLIRGs
- Short Name:
- J/A+A/595/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report rest-frame submillimeter H_2_O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z~2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H_2_O emission lines. These include five 3_21_-3_12_ ortho-H_2_O lines (Eup/k=305K) and nine J=2 para-H_2_O lines, either 2_02_-1_11_ (E_up/k=101K) or 2_11_-2_02_ (E_up/k = 137K). The apparent luminosities of the H_2_O emission lines are {mu}L_H2O_~6-21x10^8^L_{sun}_ (3<{mu}<15, where {mu} is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15Jy.km/s. We have also observed CO emission lines using EMIR on the IRAM 30m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H_2_O lines are found to be similar, generally within 1{sigma} errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H_2_O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H_2_O (LH_2_O) and infrared (LIR) that LH_2_O~LIR^(1.1-1.2)^, with our new detections. This correlation could be explained by a dominant role of far-infrared pumping in the H_2_O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature T_warm_~45-75K, H_2_O column density per unit velocity interval N_H2O_/{DELTA}V>~0.3x10^15^km/s/cm^2^ and 100{mu}m continuum opacity {tau}_100_>1 (optically thick), indicating that H_2_O is likely to trace highly obscured warm dense gas. However, further observations of J>=4 H_2_O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H_2_O^+^ emission in three sources. A tight correlation between L_H_2_O and L_H_2_O^+^ has been found in galaxies from low to high redshift. The velocity-integrated flux density ratio between H_2_O^+^ and H_2_O suggests that cosmic rays generated by strong star formation are possibly driving the H_2_O^+^ formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/1462
- Title:
- HOPS. III. Dense molecular gas properties
- Short Name:
- J/MNRAS/470/1462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The H_2_O Southern Galactic Plane Survey (HOPS) has mapped 100deg^2^ of the Galactic plane for water masers and thermal molecular line emission using the 22m Mopra telescope. We describe the automated spectral-line fitting pipelines used to determine the properties of emission detected in HOPS data cubes, and use these to derive the physical and kinematic properties of gas in the survey. A combination of the angular resolution, sensitivity, velocity resolution and high critical density of lines targeted make the HOPS data cubes ideally suited to finding precursor clouds to the most massive and dense stellar clusters in the Galaxy. We compile a list of the most massive HOPS ammonia regions and investigate whether any may be young massive cluster progenitor gas clouds. HOPS is also ideally suited to trace the flows of dense gas in the Galactic Centre. We find the kinematic structure of gas within the inner 500pc of the Galaxy is consistent with recent predictions for the dynamical evolution of gas flows in the centre of the Milky Way. We confirm a recent finding that the dense gas in the inner 100pc has an oscillatory kinematic structure with characteristic length-scale of 20pc, and also identify similar oscillatory kinematic structure in the gas at radii larger than 100pc. Finally, we make all of the above fits and the remaining HOPS data cubes across the 100deg^2^ of the survey available to the community.
