The Physical Conditions of Intermediate-Redshift M[CLC]g[/CLC] [CSC]ii[/CSC] Absorbing Clouds from Voigt Profile Analysis

Churchill, Christopher W.; Vogt, Steven S.; Charlton, Jane C.

doi:10.1086/345513

Cited by 116 publications

(161 citation statements)

References 37 publications

Supporting

Mentioning

145

Contrasting

Order By: Relevance

“…In case of Ca ii the power-law slope, β Ca ii = −2.2, is steeper than the value derived by Richter et al (2011, β Ca ii = −1.7) and that obtained for Mg ii, β Mg ii = −1.59 ± 0.05 (Churchill et al 2003), inferred from strong Mg ii absorbers at intermediate redshifts (z = 0.4−1.2). As discussed in Sect.…”

contrasting

confidence: 57%

“…We can now compare our CDD functions with the results of Churchill et al (2003) for Mg ii and with those of Richter et al (2011) for Ca ii. In case of Ca ii the power-law slope, β Ca ii = −2.2, is steeper than the value derived by Richter et al (2011, β Ca ii = −1.7) and that obtained for Mg ii, β Mg ii = −1.59 ± 0.05 (Churchill et al 2003), inferred from strong Mg ii absorbers at intermediate redshifts (z = 0.4−1.2).…”

mentioning

confidence: 95%

See 1 more Smart Citation

An absorption-selected survey of neutral gas in the Milky Way halo

Bekhti

Winkel

Richter

et al. 2012

A&A

View full text Add to dashboard Cite

Aims. We aim at analysing systematically the distribution and physical properties of neutral and mildly ionised gas in the Milky Way halo, based on a large absorption-selected data set. Methods.Multi-wavelength studies were performed combining optical absorption line data of Ca ii and Na i with follow-up H i 21-cm emission line observations along 408 sight lines towards low-and high-redshift QSOs. We made use of archival optical spectra obtained with UVES/VLT. H i data were extracted from the Effelsberg-Bonn H i survey and the Galactic All-Sky survey.For selected sight lines we obtained deeper follow-up observations using the Effelsberg 100-m telescope.Results. Ca ii (Na i) halo absorbers at intermediate and high radial velocities are present in 40-55% (20-35%) of the sightlines, depending on the column density threshold chosen. Many halo absorbers show multi-component absorption lines, indicating the presence of sub-structure. In 65% of the cases, absorption is associated with H i 21-cm emission. The Ca ii (Na i) column density distribution function follows a power-law with a slope of β ≈ −2.2 (−1.4). Conclusions. Our absorption-selected survey confirms our previous results that the Milky Way halo is filled with a large number of neutral gas structures whose high column density tail represents the population of common H i high-and intermediate-velocity clouds seen in 21-cm observations. We find that Na i/Ca ii column density ratios in the halo absorbers are typically smaller than those in the Milky Way disc, in the gas in the Magellanic Clouds, and in damped Lyman α systems. The small ratios (prominent in particular in high-velocity components) indicate a lower level of Ca depletion onto dust grains in Milky Way halo absorbers compared to gas in discs and inner regions of galaxies.

show abstract

contrasting

confidence: 57%

mentioning

confidence: 95%

An absorption-selected survey of neutral gas in the Milky Way halo

Bekhti

Winkel

Richter

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…Even if one considers the longer absorption path length through a galaxy halo from an exterior vantage point (Churchill et al study) compared to the path length through the Milky Way halo from the position of the Sun (our study), the four-times higher number of absorption components per system clearly indicates that the majority of the strong Mg ii absorbers with log N(H i) ≤ 20.2 studied by Churchill et al (2003) trace gaseous structures in halos the are kinematically more complex than the Galactic HVC population. As we will see later, this scenario is supported by the very large absorption cross section of strong Mg ii absorbers that are both more common and spatially more extended (Sect.…”

Section: Sub-component Structurementioning

confidence: 65%

“…Using highresolution optical spectra, Churchill et al (2003) indeed find a much larger number of ∼8 absorption components per absorption systems for strong Mg ii absorbers with H i column densities below that expected for neutral gas discs, but similar to those in Galactic HVCs.…”

Section: Sub-component Structurementioning

confidence: 67%

See 1 more Smart Citation

The Milky Way halo as a QSO absorption-line system

Herenz¹,

Richter²,

Charlton³

et al. 2013

A&A

View full text Add to dashboard Cite

We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low-and intermediate ions (O i, C ii, Si ii, Mg ii, Fe ii, Si iii, C iv, and Si iv) in the range f c = 0.20−0.70. For detailed analysis we concentrate on Si ii absorption components in HVCs, for which we investigate the distribution of column densities, b-values, and radial velocities. Combining information for Si ii and Mg ii, and using a geometrical HVC model we investigate the contribution of HVCs to the absorption cross section of strong Mg ii absorbers in the local Universe. We estimate that the Galactic HVCs would contribute on average ∼52 percent to the total strong Mg ii cross section of the Milky Way, if our Galaxy were to be observed from an exterior vantage point. We further estimate that the mean projected covering fraction of strong Mg ii absorption in the Milky Way halo and disc from an exterior vantage point is f c,sMgII = 0.31 for a halo radius of R = 61 kpc. These numbers, together with the observed number density of strong Mg ii absorbers at low redshift, indicate that the contribution of infalling gas clouds (i.e., HVC analogues) in the halos of Milky Way-type galaxies to the cross section of strong Mg ii absorbers is < 34 percent.These findings are in line with the idea that outflowing gas (e.g., produced by galactic winds) in the halos of more actively star-forming galaxies dominate the absorption-cross section of strong Mg ii absorbers in the local Universe.

show abstract

On the Origin of Gaseous Galaxy Halos – Low‐Column Density Gas in the Milky Way Halo

Bekhti

Winkel

Richter

et al. 2011

Reviews in Modern Astronomy

View full text Add to dashboard Cite

Recent observations show that spiral galaxies are surrounded by extended gaseous halos as predicted by the hierarchical structure formation scenario. The origin and nature of extraplanar gas is often unclear since the halo is continuously fueled by different circulation processes as part of the on-going formation and evolution of galaxies (e.g., outflows, galaxy merging, and gas accretion from the intergalactic medium). We use the Milky Way as a laboratory to study neutral and mildly ionised gas located in the inner and outer halo. Using spectral line absorption and emission measurements in different wavelength regimes we obtain detailed information on the physical conditions and the distribution of the gas. Such studies are crucial for our understanding of the complex interplay between galaxies and their gaseous environment as part of the formation and evolution of galaxies. Our analysis suggests that the column-density distribution and physical properties of gas in the Milky Way halo are very similar to that around other disk galaxies at low and high redshifts.

show abstract

The Physical Conditions of Intermediate-Redshift M[CLC]g[/CLC] [CSC]ii[/CSC] Absorbing Clouds from Voigt Profile Analysis

Cited by 116 publications

References 37 publications

An absorption-selected survey of neutral gas in the Milky Way halo

An absorption-selected survey of neutral gas in the Milky Way halo

The Milky Way halo as a QSO absorption-line system

On the Origin of Gaseous Galaxy Halos – Low‐Column Density Gas in the Milky Way Halo

Contact Info

Product

Resources

About