scholarly journals Modelling intergalactic low ionization metal absorption line systems near the epoch of reionization

2021 ◽  
Vol 502 (1) ◽  
pp. 888-903
Author(s):  
Teresita Suarez ◽  
Avery Meiksin
Keyword(s):  
Radiative Transfer ◽  
Numerical Simulations ◽  
Absorption Line ◽  
Column Density ◽  
Massive Star ◽  
Good Description ◽  
Chemical Abundances ◽  
Metal Absorption ◽  
Density Ratios ◽  
Galactic Haloes

ABSTRACT We interpret observations of intergalactic low ionization metal absorption systems at redshifts z ≳ 5 in terms of pressure-confined clouds. We find clouds confined by the expected pressure of galactic haloes with masses $11\lt \log M_h/h^{-1}\, \mathrm{M}_\odot \lt 12$ provide a good description of the column density ratios between low ionization metal absorbers. Some of the ratios, however, require extending conventional radiative transfer models of irradiated slabs to spherical (or cylindrical) clouds to allow for lines of sight passing outside the cores of the clouds. Moderate depletion of silicon on to dust grains is also indicated in some systems. The chemical abundances inferred span the range between solar and massive-star-dominated stellar populations as may arise in starburst galaxies. The typical H i column densities matching the data correspond to damped Ly α absorbers (DLAs) or sub-DLAs, with sizes of 40 pc to 3 kpc, gas masses 3.5 < log Mc/M⊙ < 8 and metallicites $0.001\!-\!0.01\, \mathrm{Z}_\odot$. Such systems continue to pose a challenge for galaxy-scale numerical simulations to reproduce.

scholarly journals Molecules in Damped Lyα Systems: Spatial Distribution

2004 ◽  
Vol 217 ◽  
pp. 270-271
Author(s):  
Hiroyuki Hirashita ◽  
Andrea Ferrara ◽  
Keiichi Wada ◽  
Philipp Richter
Keyword(s):  
Spatial Distribution ◽  
Detection Limit ◽  
Density Distribution ◽  
Numerical Simulations ◽  
Absorption Line ◽  
Column Density ◽  
High Redshift ◽  
Disk Surface ◽  
Relative Paucity ◽  
Gas Ratio

To interpret H2 quasar absorption line observations in DLAs (damped Lyα clouds), we model the H2 spatial distribution within a DLA. Based on numerical simulations of disk structures with parameters similar to those derived for such absorbers, we calculate the H2 distribution as a function of ultraviolet background (UVB) intensity and dust-to-gas ratio. For typical values of these two quantities we find that the area in which the H2 fraction exceeds 10−6 (typical observational detection limit) only covers < 10% of the disk surface, i.e., H2 has a very inhomogeneous, clumpy distribution even at these low abundance levels. This explains the relative paucity of H2 detections in DLAs. We also show the dependence of the covering fraction of H2 on dust-to-gas ratio and UVB intensity and we comment on the physics governing the H2 chemical network at high redshift. We finally comment on our implication on the statistics of the H2 column density distribution.

scholarly journals C18O, 13CO, and 12CO abundances and excitation temperatures in the Orion B molecular cloud

2020 ◽  
Vol 645 ◽  
pp. A26 ◽  
Author(s):  
Antoine Roueff ◽  
Maryvonne Gerin ◽  
Pierre Gratier ◽  
François Levrier ◽  
Jérôme Pety ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Column Density ◽  
Spectral Lines ◽  
Chemical Fractionation ◽  
Physical Parameters ◽  
Elemental Ratios ◽  
Density Ratios ◽  
Cramer Rao Bound

Context. CO isotopologue transitions are routinely observed in molecular clouds for the purpose of probing the column density of the gas and the elemental ratios of carbon and oxygen, in addition to tracing the kinematics of the environment. Aims. Our study is aimed at estimating the abundances, excitation temperatures, velocity field, and velocity dispersions of the three main CO isotopologues towards a subset of the Orion B molecular cloud, which includes IC 434, NGC 2023, and the Horsehead pillar. Methods. We used the Cramer Rao bound (CRB) technique to analyze and estimate the precision of the physical parameters in the framework of local-thermodynamic-equilibrium (LTE) excitation and radiative transfer with added white Gaussian noise. We propose a maximum likelihood estimator to infer the physical conditions from the 1–0 and 2–1 transitions of CO isotopologues. Simulations show that this estimator is unbiased and proves efficient for a common range of excitation temperatures and column densities (Tex > 6 K, N > 1014−1015  cm−2). Results. Contrary to general assumptions, the various CO isotopologues have distinct excitation temperatures and the line intensity ratios between different isotopologues do not accurately reflect the column density ratios. We find mean fractional abundances that are consistent with previous determinations towards other molecular clouds. However, significant local deviations are inferred, not only in regions exposed to the UV radiation field, but also in shielded regions. These deviations result from the competition between selective photodissociation, chemical fractionation, and depletion on grain surfaces. We observe that the velocity dispersion of the C18O emission is 10% smaller than that of 13CO. The substantial gain resulting from the simultaneous analysis of two different rotational transitions of the same species is rigorously quantified. Conclusions. The CRB technique is a promising avenue for analyzing the estimation of physical parameters from the fit of spectral lines. Future works will generalize its application to non-LTE excitation and radiative transfer methods.

scholarly journals The stratified disc wind of MCG-03-58-007

2020 ◽  
Vol 500 (1) ◽  
pp. 291-300
Author(s):  
V Braito ◽  
J N Reeves ◽  
P Severgnini ◽  
R Della Ceca ◽  
L Ballo ◽  
...  
Keyword(s):  
Absorption Line ◽  
Velocity Component ◽  
Column Density ◽  
Accretion Disc ◽  
Line Profiles ◽  
Lower Velocity ◽  
Multiple Observations ◽  
Two Phases ◽  
The One ◽  
High Column

ABSTRACT Past Suzaku, XMM–Newton, and NuSTAR observations of the nearby (z = 0.03233) bright Seyfert 2 galaxy MCG-03-58-007 revealed the presence of two deep and blue-shifted iron K-shell absorption line profiles. These could be explained with the presence of two phases of a highly ionized, high column density accretion disc wind outflowing with vout1 ∼ −0.1c and vout2 ∼ −0.2c. Here we present two new observations of MCG-03-58-007: one was carried out in 2016 with Chandra and one in 2018 with Swift. Both caught MCG-03-58-007 in a brighter state ($F_{{\mathrm{2}-10\, keV}} \sim 4 \times 10^{-12}$ erg cm−2 s−1) confirming the presence of the fast disc wind. The multi-epoch observations of MCG-03-58-007 covering the period from 2010 to 2018 were then analysed. These data show that the lower velocity component outflowing with vout1 ∼ −0.072 ± 0.002c is persistent and detected in all the observations, although it is variable in column density in the range NH ∼ 3–8 × 1023 cm−2. In the 2016 Swift observation we detected again the second faster component outflowing with vout2 ∼ −0.2c, with a column density ($N_{\mbox{H}}=7.0^{+5.6}_{-4.1}\times 10^{23}$ cm−2), similar to that seen during the Suzaku observation. However during the Chandra observation 2 yr earlier, this zone was not present (NH &lt; 1.5 × 1023 cm−2), suggesting that this faster zone is intermittent. Overall the multi-epochs observations show that the disc wind in MCG-03-58-007 is not only powerful, but also extremely variable, hence placing MCG-03-58-007 among unique disc winds such as the one seen in the famous QSO PDS456. One of the main results of this investigation is the consideration that these winds could be extremely variable, sometime appearing and sometime disappearing; thus to reach solid and firm conclusions about their energetics multiple observations are mandatory.

scholarly journals Erratum: Chemical abundances in QSO host galaxies and environments from narrow absorption line systems

2004 ◽  
Vol 355 (4) ◽  
pp. 1399-1399
Author(s):  
Valentina D'Odorico ◽  
Stefano Cristiani ◽  
Donatella Romano ◽  
Gian Luigi Granato ◽  
Luigi Danese
Keyword(s):  
Absorption Line ◽  
Host Galaxies ◽  
Chemical Abundances

scholarly journals Measuring Outer Disk Warps with Optical Spectroscopy

2008 ◽  
Vol 4 (S254) ◽  
pp. 283-288
Author(s):  
Daniel Christlein ◽  
Joss Bland-Hawthorn
Keyword(s):  
Star Formation ◽  
Optical Spectroscopy ◽  
Column Density ◽  
Rotational Velocity ◽  
Chemical Abundances ◽  
Circular Velocity ◽  
Outer Disk ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Interesting Alternative

AbstractWarps in the outer gaseous disks of galaxies are a ubiquitous phenomenon, but it is still unclear what generates them. One theory is that warps are generated internally through spontaneous bending instabilities. Other theories suggest that they result from the interaction of the outer disk with accreting extragalactic material. In this case, we expect to find cases where the circular velocity of the warp gas is poorly correlated with the rotational velocity of the galaxy disk at the same radius. Optical spectroscopy presents itself as an interesting alternative to 21-cm observations for testing this prediction, because (i) separating the kinematics of the warp from those of the disk requires a spatial resolution that is higher than what is achieved at 21 cm at low HI column density; (ii) optical spectroscopy also provides important information on star formation rates, gas excitation, and chemical abundances, which provide clues to the origin of the gas in warps. We present here preliminary results of a study of the kinematics of gas in the outer-disk warps of seven edge-on galaxies, using multi-hour VLT/FORS2 spectroscopy.

scholarly journals Investigation of chemical differentiation among the NGC 2264 cluster-forming clumps

2020 ◽  
Vol 493 (2) ◽  
pp. 2395-2409 ◽  
Author(s):  
Kotomi Taniguchi ◽  
Adele Plunkett ◽  
Eric Herbst ◽  
Kazuhito Dobashi ◽  
Tomomi Shimoikura ◽  
...  
Keyword(s):  
Column Density ◽  
Point Sources ◽  
Emission Lines ◽  
Filamentary Structure ◽  
Molecular Emission ◽  
Sky Survey ◽  
Integrated Intensity ◽  
Positive Correlations ◽  
Density Ratios ◽  
Massive Cluster

ABSTRACT We have carried out mapping observations of molecular emission lines of HC3N and CH3OH toward two massive cluster-forming clumps, NGC 2264-C and NGC 2264-D, using the Nobeyama 45-m radio telescope. We derive an I(HC3N)/I(CH3OH) integrated intensity ratio map, showing a higher value at clumps including 2MASS (Two Micron All Sky Survey) point sources at the northern part of NGC 2264-D. Possible interpretations of the I(HC3N)/I(CH3OH) ratio are discussed. We have also observed molecular emission lines from CCS and N2H+ toward five positions in each clump. We investigate the N(N2H+)/N(CCS) and N(N2H+)/N(HC3N) column density ratios among the ten positions in order to test whether they can be used as chemical evolutionary indicators in these clumps. The N(N2H+)/N(CCS) ratio shows a very high value toward a bright embedded IR source (IRS1), whereas the N(N2H+)/N(HC3N) ratio at IRS1 is comparable with those at the other positions. These results suggest that ultraviolet radiation affects the chemistry around IRS1. We find that there are positive correlations between these column density ratios and the excitation temperatures of N2H+, which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reflect the combination of evolution along the filamentary structure and evolution of each clump.

scholarly journals Observations of Highly-Ionized Interstellar Iron

1984 ◽  
Vol 81 ◽  
pp. 189-191
Author(s):  
L.M. Hobbs
Keyword(s):  
Radial Velocity ◽  
Absorption Line ◽  
Equivalent Width ◽  
Column Density ◽  
Light Path ◽  
Interstellar Gas ◽  
X Ray ◽  
X Ray Background ◽  
Multi Phase ◽  
No Absorption

AbstractThe spectra of 24 stars, including 5 at distances d < 200 pc, have been observed in the regions of the coronal [Fe X] λ6375 and [Fe XIV] λ5303 lines at detection limits near an equivalent width of 1 mÅ in the best cases. In general agreement with predictions based on a multi-phase model of the interstellar medium, no absorption which can be attributed to Fe X or Fe XIV ions in hot interstellar gas emitting the soft x-ray background is seen in any of these spectra, except for two. Toward λ Cephei an absorption line near λ6375 is measured with an equivalent width of 8.1 ± 2 mÅ, a width corresponding to 20 ± 5 km s-1 or a temperature T ≤ (0.5 ± 0.25) x 106 °K, and, if it is caused by Fe X ions, a radial velocity of -355 km s-1. On that hypothesis, the hot interstellar gas constitutes at least 63% of the column density of gas along this light path.

Xvoigt: An Interactive Absorption Line Fitting Program for the X Window System

1995 ◽  
Vol 12 (2) ◽  
pp. 239-243 ◽  
Author(s):  
David P. Max ◽  
Geoff Bailey
Keyword(s):  
Absorption Line ◽  
Column Density ◽  
Velocity Dispersion ◽  
Absorption Lines ◽  
Signal To Noise ◽  
Window System ◽  
Profile Fitting ◽  
X Window ◽  
Line Fitting ◽  
Line Analysis

AbstractWe have developed an easy-to-use, mouse-driven program for the interactive fitting of interstellar absorption lines in high-resolution astronomical spectra. The program, Xvoigt, gives values for the column density and velocity dispersion of the absorbing clouds. It runs under the popular X Window system available on most workstations, and offers significant enhancements over existing profile-fitting software. Xvoigt can be an important adjunct to automatic programs for fitting absorption lines in low to moderate signal-to-noise QSO or other spectra, and is ideal for demonstrating the details and difficulties of absorption line analysis.

scholarly journals Pair lines of sight observations of multiphase gas bearing O vi in a galaxy environment

2021 ◽  
Vol 503 (3) ◽  
pp. 3243-3261
Author(s):  
Pratyush Anshul ◽  
Anand Narayanan ◽  
Sowgat Muzahid ◽  
Alexander Beckett ◽  
Simon L Morris
Keyword(s):  
Column Density ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Angular Separation ◽  
The Other ◽  
Chemical Abundances ◽  
Lower Column ◽  
Solar Metallicity ◽  
Galaxy Environment ◽  
Collisional Ionization

ABSTRACT Using HST/COS spectra of the twin quasar lines of sight Q 0107–025A & Q 0107–025B, we report on the physical properties, chemical abundances, and transverse sizes of a multiphase medium in a galaxy field at z = 0.399. The angular separation between the quasars corresponds to a physical separation of 520 kpc at the absorber redshift. The absorber towards Q 0107–025B is a partial Lyman limit system (pLLS) with $\log N({\mathrm{H}}{\small I})/\hbox{cm$^{-2}$}\approx 16.8$. The H i column density in the absorber along the other sightline is ≈ 2 orders of magnitude lower. The O vi along both sightlines have comparable column densities and broad b-values (b &gt; 30 km s−1) whereas the low ionization lines are considerably narrower. The low ionization gas is inconsistent with the O vi when modelled assuming photoionization from the same phase. In both lines of sight, O vi and the broad H i coinciding, are best explained through collisional ionization in a cooling plasma with solar metallicity. Ionization models infer 1/10th solar metallicity for the pLLS and solar metallicity for the lower column density absorber along the other sightline. Within ± 250 km s−1 and 2 Mpc of projected distance from the sightlines 12 galaxies are identified, of which five are within 500 kpc. The twin sightlines are at normalized impact parameters of ρ ∼ 1.1Rvir, and ρ ∼ 0.8Rvir from a M* ∼ 1010.7 M⊙, L ∼ 0.07L*, and star formation rate (SFR) &lt; 0.1 M⊙ yr−1 galaxy, potentially probing its CGM (circumgalactic medium). The next closest in normalized separation are a dwarf galaxy with M* ∼ 108.7 M⊙, and SFR ∼ 0.06 M⊙ yr−1, and an intermediate mass galaxy with M* ∼ 1010.0 M⊙, and SFR ∼ 3 M⊙ yr−1. Along both sightlines, O vi could be either tracing narrow transition temperature zones at the interface of low ionization gas and the hot halo of nearest galaxy, or a more spread-out warm component that could be gas bound to the circumgalactic halo or the intragroup medium. The latter scenarios lead to a warm gas mass limit of M ≳ 4.5 × 109 M⊙.

Sign in / Sign up

Export Citation Format

Share Document