TY  - JOUR
A1  - Muzahid, S.
A1  - Fonseca, G.
A1  - Roberts, A.
A1  - Rosenwasser, B.
A1  - Richter, Philipp
A1  - Narayanan, A.
A1  - Churchill, C.
A1  - Charlton, J.
T1  - COS-Weak: probing the CGM using analogues of weak Mg II absorbers at z < 0.3
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present a sample of 34 weak metal line absorbers at z < 0.3 selected by the simultaneous >3σ detections of the Si iiλ1260 and C iiλ1334 absorption lines, with Wr(SiII)<0.2 Å and Wr(CII)<0.3 Å, in archival HST/COS spectra. Our sample increases the number of known low-z ‘weak absorbers’ by a factor of >5. The column densities of H i and low-ionization metal lines obtained from Voigt profile fitting are used to build simple photoionization models. The inferred densities and line-of-sight thicknesses of the absorbers are in the ranges of −3.3 < log nH/cm−3 < −2.4 and ∼1 pc–50 kpc (median ≈500 pc), respectively. Most importantly, 85 per cent (50 per cent) of these absorbers show a metallicity of [Si/H]>−1.0(0.0)⁠. The fraction of systems showing near-/supersolar metallicity in our sample is significantly higher than in the H i-selected sample of Wotta et al., and the galaxy-selected sample of Prochaska et al., of absorbers probing the circum-galactic medium at similar redshift. A search for galaxies has revealed a significant galaxy-overdensity around these weak absorbers compared to random positions with a median impact parameter of 166 kpc from the nearest galaxy. Moreover, we find the presence of multiple galaxies in ≈80 per cent of the cases, suggesting group environments. The observed dN/dz of 0.8 ± 0.2 indicates that such metal-enriched, compact, dense structures are ubiquitous in the haloes of low-z group galaxies. We suggest that these are transient structures that are related to galactic outflows and/or stripping of metal-rich gas from galaxies.
KW  - galaxies: formation
KW  - galaxies: haloes
KW  - quasar: absorption line
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty529
SN  - 0035-8711
SN  - 1365-2966
VL  - 476
IS  - 4
SP  - 4965
EP  - 4986
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Paalvast, M.
A1  - Verhamme, A.
A1  - Straka, L. A.
A1  - Brinchmann, J.
A1  - Herenz, Edmund Christian
A1  - Carton, D.
A1  - Gunawardhana, M. L. P.
A1  - Boogaard, L. A.
A1  - Cantalupo, S.
A1  - Contini, T.
A1  - Epinat, Benoit
A1  - Inami, H.
A1  - Marino, R. A.
A1  - Maseda, M. V.
A1  - Michel-Dansac, L.
A1  - Muzahid, S.
A1  - Nanayakkara, T.
A1  - Pezzulli, Gabriele
A1  - Richard, J.
A1  - Schaye, Joop
A1  - Segers, M. C.
A1  - Urrutia, Tanya
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - Properties and redshift evolution of star-forming galaxies with high [0 III]/[O II] ratios with MUSE at 0.28 < z < 0.85
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We present a study of the [O III]/[O II] ratios of star-forming galaxies drawn from Multi-Unit Spectroscopic Explorer (MUSE) data spanning a redshift range 0.28 < z < 0.85. Recently discovered Lyman continuum (LyC) emitters have extremely high oxygen line ratios: [O III]lambda 5007/[O II]lambda lambda 3726, 3729 > 4. Here we aim to understand the properties and the occurrences of galaxies with such high line ratios. Combining data from several MUSE Guaranteed Time Observing (GTO) programmes, we select a population of star-forming galaxies with bright emission lines, from which we draw 406 galaxies for our analysis based on their position in the z-dependent star formation rate (SFR) stellar mass (M*) plane. Out of this sample 15 are identified as extreme oxygen emitters based on their [O III]/[O II] ratios (3.7%) and 104 galaxies have [O III]/[O II] > 1 (26%). Our analysis shows no significant correlation between M*, SFR, and the distance from the SFR M, relation with [O III]/[O II]. We find a decrease in the fraction of galaxies with [O III]/[O II] > 1 with increasing M*, however, this is most likely a result of the relationship between [O III]/[O II] and metallicity, rather than between [O III]/[O II] and M. We draw a comparison sample of local analogues with < z > 0.03 from the Sloan Digital Sky Survey, and find similar incidence rates for this sample. In order to investigate the evolution in the fraction of high [O III]/[O II] emitters with redshift, we bin the sample into three redshift subsamples of equal number, but find no evidence for a dependence on redshift. Furthermore, we compare the observed line ratios with those predicted by nebular models with no LyC escape and find that most of the extreme oxygen emitters can be reproduced by low metallicity models. The remaining galaxies are likely LyC emitter candidates.
KW  - galaxies: evolution
KW  - galaxies: ISM
KW  - galaxies: abundances
KW  - ISM: structure
KW  - ISM: kinematics and dynamics
KW  - dark ages, reionization, first stars
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201832866
SN  - 0004-6361
SN  - 1432-0746
VL  - 618
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Richter, Philipp
A1  - Nuza, S. E.
A1  - Fox, Andrew J.
A1  - Wakker, Bart P.
A1  - Lehner, N.
A1  - Ben Bekhti, Nadya
A1  - Fechner, Cora
A1  - Wendt, Martin
A1  - Howk, J. Christopher
A1  - Muzahid, S.
A1  - Ganguly, R.
A1  - Charlton, Jane C.
T1  - An HST/COS legacy survey of high-velocity ultraviolet absorption in the
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. The Milky Way is surrounded by large amounts of diffuse gaseous matter that connects the stellar body of our Galaxy with its large-scale Local Group (LG) environment. Aims. To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21 cm radio observations of neutral hydrogen. Methods. Along 270 sightlines we measure metal absorption in the lines of Si II, Si III, C II, and C IV and associated H I 21 cm emission in HVCs in the velocity range vertical bar v(LSR)vertical bar = 100-500 km s(-1). With this unprecedented large HVC sample we were able to improve the statistics on HVC covering fractions, ionization conditions, small-scale structure, CGM mass, and inflow rate. For the first time, we determine robustly the angular two point correlation function of the high-velocity absorbers, systematically analyze antipodal sightlines on the celestial sphere, and compare the HVC absorption characteristics with that of damped Lyman alpha absorbers (DLAs) and constrained cosmological simulations of the LG (CLUES project).
KW  - Galaxy: halo
KW  - Galaxy: structure
KW  - Galaxy: evolution
KW  - ISM: kinematics and dynamics
KW  - techniques: spectroscopic
KW  - ultraviolet: ISM
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201630081
SN  - 1432-0746
VL  - 607
PB  - EDP Sciences
CY  - Les Ulis
ER  -