TY  - JOUR
A1  - Izotov, Y. I.
A1  - Schaerer, Daniel
A1  - Worseck, Gabor
A1  - Guseva, N. G.
A1  - Thuan, T. X.
A1  - Verhamme, A.
A1  - Orlitova, I.
A1  - Fricke, K. J.
T1  - J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons
JF  - Monthly notices of the Royal Astronomical Society
N2  - We report the detection of the Lyman continuum (LyC) radiation of the compact star-forming galaxy (SFG) J1154+2443 observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. This galaxy, at a redshift of z = 0.3690, is characterized by a high emission-line flux ratio O-32 = [O III] lambda 5007/[O II] lambda 3727 = 11.5. The escape fraction of the LyC radiation f(esc)(LyC) in this galaxy is 46 per cent, the highest value found so far in low-redshift SFGs and one of the highest values found in galaxies at any redshift. The narrow double-peaked Ly alpha emission line is detected in the spectrum of J1154+2443 with a separation between the peaks V-sep of 199 km s(-1), one of the lowest known for Ly alpha-emitting galaxies, implying a high f(esc)(Ly alpha). Comparing the extinction-corrected Ly alpha/H beta flux ratio with the case B value, we find f(esc)(Ly alpha) = 98 per cent. Our observations, combined with previous detections in the literature, reveal an increase of O-32 with increasing f(esc)(LyC). We also find a tight anticorrelation between f(esc)(LyC) and V-sep. The surface brightness profile derived from the COS acquisition image reveals a bright star-forming region in the centre and an exponential disc in the outskirts with a disc scale length alpha = 1.09 kpc. J1154+2443, compared to other known low-redshift LyC leakers, is characterized by the lowest metallicity, 12+log O/H = 7.65 +/- 0.01, the lowest stellar mass M-star = 108.20 M-circle dot, a similar star formation rate SFR = 18.9 M-circle dot yr(-1), and a high specific SFR of 1.2 x 10(-7) yr(-1).
KW  - galaxies: abundances
KW  - galaxies: dwarf
KW  - galaxies: fundamental parameters
KW  - galaxies: ISM
KW  - galaxies: starburst
KW  - dark ages, reionization, first stars
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx3115
SN  - 0035-8711
SN  - 1365-2966
VL  - 474
IS  - 4
SP  - 4514
EP  - 4527
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Weilbacher, Peter Michael
A1  - Monreal-Ibero, Ana
A1  - Verhamme, Anne
A1  - Sandin, Christer
A1  - Steinmetz, Matthias
A1  - Kollatschny, Wolfram
A1  - Krajnovic, Davor
A1  - Kamann, Sebastian
A1  - Roth, Martin M.
A1  - Erroz-Ferrer, Santiago
A1  - Marino, Raffaella Anna
A1  - Maseda, Michael V.
A1  - Wendt, Martin
A1  - Bacon, Roland
A1  - Dreizler, Stefan
A1  - Richard, Johan
A1  - Wisotzki, Lutz
T1  - Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae galaxy
JF  - Astronomy and astrophysics : an international weekly journal
N2  - The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect H II regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of H II regions, showing fainter luminosities. By comparing H II region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each H II region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking H II regions for the diffuse ionized gas in the Antennae.
KW  - galaxies: interactions
KW  - galaxies: individual: NGC 4038, NGC 4039
KW  - galaxies: ISM
KW  - ISM: structure
KW  - H II regions
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201731669
SN  - 1432-0746
VL  - 611
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Monreal-Ibero, Ana
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
T1  - Diffuse interstellar bands lambda 5780 and lambda 5797 in the Antennae Galaxy as seen by MUSE
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Diffuse interstellar bands (DIBs) are faint spectral absorption features of unknown origin. Research on DIBs beyond the Local Group is very limited and will surely blossom in the era of the Extremely Large Telescopes. However, we can already start paving the way. One possibility that needs to be explored is the use of high-sensitivity integral field spectrographs. Aims. Our goals are twofold. First, we aim to derive reliable mapping of at least one DIB in a galaxy outside the Local Group. Second, we want to explore the relation between DIBs and other properties of the interstellar medium (ISM) in the galaxy. Methods. We use Multi Unit Spectroscopic Explorer (MUSE) data for the Antennae Galaxy, the closest major galaxy merger. High signal-to-noise spectra were created by co-adding the signal of many spatial elements with the Voronoi binning technique. The emission of the underlying stellar population was modelled and substracted with the STARLIGHT spectral synthesis code. Flux and equivalent width of the features of interest were measured by means of fitting to Gaussian functions. Conclusions. The results illustrate the enormous potential of integral field spectrographs for extragalactic DIB research.
KW  - dust, extinction
KW  - ISM: lines and bands
KW  - galaxies: ISM
KW  - galaxies: individual: Antennae Galaxy
KW  - galaxies: interactions
KW  - ISM: structure
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201732178
SN  - 1432-0746
VL  - 615
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Izotov, Y. I.
A1  - Worseck, Gábor
A1  - Schaerer, Daniel
A1  - Guseva, N. G.
A1  - Thuan, T. X.
A1  - Fricke, K. J.
A1  - Verhamme, Anne
A1  - Orlitova, I.
T1  - Low-redshift Lyman continuum leaking galaxies with high [O III]/[O II] ratios
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present observations with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope of five star-forming galaxies at redshifts z in the range 0.2993-0.4317 and with high emission-line flux ratios O-32 = [O III]lambda 5007/[O II]lambda 3727 similar to 8-27 aiming to detect the Lyman continuum (LyC) emission. We detect LyC emission in all galaxies with the escape fractions f(esc)(LyC) in a range of 2-72 per cent. A narrow Ly alpha emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution COS spectra with a velocity separation between the peaks V-sep varying from similar to 153 to similar to 345 km s(-1). We find a general increase of the LyC escape fraction with increasing O-32 and decreasing stellar mass M-star, but with a large scatter of f(esc)(LyC). A tight anticorrelation is found between f(esc)(LyC) and V-sep making V-sep a good parameter for the indirect determination of the LyC escape fraction. We argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars.
KW  - galaxies: abundances
KW  - galaxies: dwarf
KW  - galaxies: fundamental parameters
KW  - galaxies: ISM
KW  - galaxies: starburst
KW  - dark ages, reionization, first stars
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty1378
SN  - 0035-8711
SN  - 1365-2966
VL  - 478
IS  - 4
SP  - 4851
EP  - 4865
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  - Berg, Trystyn A. M.
A1  - Ellison, Sara L.
A1  - Sanchez-Ramirez, Ruben
A1  - Lopez, Sebastian
A1  - Becker, George D.
A1  - Christensen, Lise
A1  - Cupani, Guido
A1  - Denney, Kelly D.
A1  - Worseck, Gabor
T1  - Sub-damped Lyman alpha systems in the XQ-100 survey - I. Identification and contribution to the cosmological H I budget
JF  - Monthly notices of the Royal Astronomical Society
KW  - galaxies: high-redshift
KW  - galaxies: ISM
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz2012
SN  - 0035-8711
SN  - 1365-2966
VL  - 488
IS  - 3
SP  - 4356
EP  - 4369
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Plat, A.
A1  - Charlot, S.
A1  - Bruzual, G.
A1  - Feltre, A.
A1  - Vidal-Garcia, A.
A1  - Morisset, C.
A1  - Chevallard, Jacopo
A1  - Todt, Helge Tobias
T1  - Constraints on the production and escape of ionizing radiation from the emission-line spectra of metal-poor star-forming galaxies
JF  - Monthly notices of the Royal Astronomical Society
N2  - We explore the production and escape of ionizing photons in young galaxies by investigating the ultraviolet and optical emission-line properties of models of ionization-bounded and density-bounded H II regions, active-galactic-nucleus (AGN) narrow-line regions, and radiative shocks computed all using the same physically consistent description of element abundances and depletion on to dust grains down to very low metallicities. We compare these models with a reference sample of metal-poor star-forming galaxies and Lyman-continuum (LyC) leakers at various redshifts, which allows the simultaneous exploration of more spectral diagnostics than typically available at once for individual subsamples. We confirm that current single- and binary-star population synthesis models do not produce hard-enough radiation to account for the high-ionization emission of the most metal-poor galaxies. Introducing either an AGN or radiative-shock component brings models into agreement with observations. A published model including X-ray binaries is an attractive alternative to reproduce the observed rise in He II lambda 4686/H beta ratio with decreasing oxygen abundance in metal-poor star-forming galaxies, but not the high observed He II lambda 4686/H beta ratios of galaxies with large EW(H beta). A source of harder ionizing radiation appears to be required in these extreme objects, such as an AGN or radiative-shock component, perhaps linked to an initial-mass-function bias towards massive stars at low metallicity. This would also account for the surprisingly high [O I]/[O III] ratios of confirmed LyC leakers relative to ionization-bounded models. We find no simple by-eye diagnostic of the nature of ionizing sources and the escape of LyC photon, which require proper simultaneous fits of several lines to be discriminated against.
KW  - galaxies: general
KW  - galaxies: high-redshift
KW  - galaxies: ISM
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz2616
SN  - 0035-8711
SN  - 1365-2966
VL  - 490
IS  - 1
SP  - 978
EP  - 1009
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Finley, Hayley
A1  - Bouche, Nicolas
A1  - Contini, Thierry
A1  - Epinat, Benoit
A1  - Bacon, Roland
A1  - Brinchmann, Jarle
A1  - Cantalupo, Sebastiano
A1  - Erroz-Ferrer, Santiago
A1  - Marino, Aella Anna
A1  - Maseda, Michael
A1  - Richard, Johan
A1  - Schroetter, Ilane
A1  - Verhamme, Anne
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - Galactic winds with MUSE: A direct detection of Fe II* emission from a z=1.29 galaxy
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. Using very deep observations (27 h) of the Hubble Deep Field South with the Multi Unit Spectroscopic Explorer (MUSE) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z = 1.29 with a stellar mass M-star = 8 x 10(9) M-circle dot, star formation rate SFR = 77(-25)(+40) M-circle dot yr(-1), and star formation rate surface brightness Sigma(SFR) = 1.6 M-circle dot kpc(-2) within the [OII] lambda lambda 3727, 3729 half-light radius R-1/2, ([OII]) = 2.76 +/- 0.17 kpc. From a component of the strong resonant Mg II and Fe II absorptions at -350 km s(-1), we infer a mass outflow rate that is comparable to the star formation rate. We detect non-resonant Fe II* emission, at lambda 2365, lambda 2396, lambda 2612, and lambda 2626, at 1.2-2.4-1.5-2.7 x 10-(18) erg s(-1) cm(-2) respectively. The flux ratios are consistent with the expectations for optically thick gas. By combining the four non-resonant Fe II* emission lines, we spatially map the Fe II* emission from an individual galaxy for the first time. The Fe II* emission has an elliptical morphology that is roughly aligned with the galaxy minor kinematic axis, and its integrated half-light radius, R-1/2, (Fe II*) = 4.1 +/- 0.4 kpc, is 70% larger than the stellar continuum (R-1/2,(star) similar or equal to 2.34 +/- 0.17) or the [O II] nebular line. Moreover, the Fe II* emission shows a blue wing extending up to -400 km s(-1), which is more pronounced along the galaxy minor kinematic axis and reveals a C-shaped pattern in a p - v diagram along that axis. These features are consistent with a bi-conical outflow.
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - galaxies: starburst
KW  - galaxies: ISM
KW  - ISM: jets and outflows
KW  - ultraviolet: ISM
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201730428
SN  - 1432-0746
VL  - 605
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Guber, Christoph R.
A1  - Richter, Philipp
T1  - Dust depletion of Ca and Ti in QSO absorption-line systems
JF  - Wiley Interdisciplinary Reviews : Water
N2  - Aims. To explore the role of titanium-and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z <= 0.5 to measure column densities (or limits) for Ca II and Ti II. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z similar to 3.8. Our absorber sample contains 110 absorbers including damped Lyman alpha systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the MilkyWay and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results. Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] approximate to 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions. We conclude that Ca II and Ti II bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems.
KW  - quasars: absorption lines
KW  - dust, extinction
KW  - galaxies: abundances
KW  - galaxies: ISM
KW  - intergalactic medium
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628466
SN  - 1432-0746
VL  - 591
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Monreal-Ibero, Ana
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
A1  - Selman, Fernando
A1  - Lallement, Rosine
A1  - Brinchmann, Jarle
A1  - Kamann, Sebastian
A1  - Sandin, Christer
T1  - Towards DIB mapping in galaxies beyond 100 Mpc A radial profile of the lambda 5780.5 diffuse interstellar band in AM1353-272 B
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Diffuse interstellar bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of the interstellar medium (ISM). Research of DIBs outside the Milky Way is currently very limited. In particular, spatially resolved investigations of DIBs outside of the Local Group are, to our knowledge, inexistent.
 Aims. In this contribution, we explore the capability of the high-sensitivity integral field spectrograph, MUSE, as a tool for mapping diffuse interstellar bands at distances larger than 100 Mpc.
 Methods. We used MUSE commissioning data for AM1353-272 B, the member with the highest extinction of the Dentist's Chair, an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings.
 Results. We derived decreasing radial profiles for the equivalent width of the lambda 5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of similar to 4.6 kpc from the centre of the galaxy. The interstellar extinction as derived from the Ha/H beta line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM1353-272 B, consistent with the currently existing global trend between these quantities when using measurements for Galactic and extragalactic sightlines.
 Conclusions. It seems feasible to map the DIB strength in the Local Universe, which has up to now only been performed for the Milky Way. This offers a new approach to studying the relationship between DIBs and other characteristics and species of the ISM in addition to using galaxies in the Local Group or sightlines towards very bright targets outside the Local Group.
KW  - dust, extinction
KW  - ISM: lines and bands
KW  - galaxies: ISM
KW  - galaxies: individual: AM1353-272 B
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201525854
SN  - 0004-6361
SN  - 1432-0746
VL  - 576
PB  - EDP Sciences
CY  - Les Ulis
ER  -