ORCID Profile
0000-0001-8415-7547
Current Organisation
Københavns Universitet Niels Bohr Instituttet
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Publisher: Oxford University Press (OUP)
Date: 28-10-2022
Abstract: We study the link between galaxies and H i-selected absorption systems at z ∼ 3–4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field spectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\\rm N_{\\rm H\\,{\\small I}}\\gtrsim 10^{16.5}~\\rm cm^{-2}$. We identify 127 Ly α emitting galaxies (LAEs) around the absorbers, corresponding to a detection rate of 82 ± 16 per cent. The luminosity function of these LAEs is ≈5 times higher in normalization than the field population and we detect a significant clustering of galaxies with respect to the gas, confirming that high column density absorbers and LAEs trace each other. Between 30 and 40 per cent of the absorbers are associated with multiple LAEs, which lie preferentially along filaments. Galaxies in groups also exhibit a three times higher covering factor of optically thick gas compared to isolated systems. No significant correlations are identified between the emission properties of LAEs and the absorption properties of optically thick gas clouds, except for a weak preference of brighter and multiple galaxies to reside near broad absorbers. Based on the measured impact parameters and the covering factor, we conclude that the near totality of optically thick gas in the Universe can be found in the outer circumgalactic medium (CGM) of LAEs or in the intergalactic medium (IGM) in proximity to these galaxies. Thus, LAEs act as tracers of larger scale structures within which both galaxies and optically thick clouds are embedded. The patchy and inhomogeneous nature of the CGM and IGM explains the lack of correlations between absorption and emission properties. This implies that very large s les are needed to unveil the trends that encode the properties of the baryon cycle.
Publisher: American Astronomical Society
Date: 26-08-2020
Publisher: American Astronomical Society
Date: 30-11-2009
Publisher: American Astronomical Society
Date: 14-10-2019
Publisher: Oxford University Press (OUP)
Date: 25-09-2017
Publisher: Oxford University Press (OUP)
Date: 30-06-2015
Publisher: American Astronomical Society
Date: 05-08-2016
Publisher: American Astronomical Society
Date: 30-03-2016
Publisher: Oxford University Press (OUP)
Date: 11-06-2018
Publisher: American Astronomical Society
Date: 20-11-2018
Publisher: Oxford University Press (OUP)
Date: 31-12-2016
Publisher: American Astronomical Society
Date: 17-10-2011
Publisher: Springer Science and Business Media LLC
Date: 25-10-2023
Publisher: Oxford University Press (OUP)
Date: 14-11-2014
Publisher: EDP Sciences
Date: 03-2023
DOI: 10.1051/0004-6361/202244205
Abstract: The study of the properties of galaxies in the first billion years after the Big Bang is one of the major topics of current astrophysics. Optical and near-infrared spectroscopy of the afterglows of long gamma-ray bursts (GRBs) provides a powerful diagnostic tool to probe the interstellar medium (ISM) of their host galaxies and foreground absorbers, even up to the highest redshifts. We analyze the VLT/X-shooter afterglow spectrum of GRB 210905A, triggered by the Neil Gehrels Swift Observatory, and detect neutral hydrogen, low-ionization, high-ionization, and fine-structure absorption lines from a complex system at z = 6.3118, which we associate with the GRB host galaxy. We use them to study the ISM properties of the host system, revealing the metallicity, kinematics, and chemical abundance pattern of its gas along the GRB line of sight. We also detect absorption lines from at least two foreground absorbers at z = 5.7390 and z = 2.8296. The total metallicity of the z ∼ 6.3 system is [M/H] tot = −1.72 ± 0.13, after correcting for dust depletion and taking α -element enhancement into account, as suggested by our analysis. This is consistent with the values found for the other two GRBs at z ∼ 6 with spectroscopic data showing metal absorption lines (GRB 050904 and GRB 130606A), and it is at the higher end of the metallicity distribution of quasar d ed Lyman- α systems (QSO-DLAs) extrapolated to such a high redshift. In addition, we determine the overall amount of dust and dust-to-metal mass ratio (DTM) ([Zn/Fe] fit = 0.33 ± 0.09 and DTM = 0.18 ± 0.03). We find indications of nucleosynthesis due to massive stars and, for some of the components of the gas clouds, we find evidence of peculiar nucleosynthesis, with an overabundance of aluminum (as also found for GRB 130606A). From the analysis of fine-structure lines, we determine distances of several kiloparsecs for the low-ionization gas clouds closest to the GRB. Those are farther distances than usually found for GRB host absorption systems, possibly due to the very high number of ionizing photons produced by the GRB that could ionize the line of sight up to several hundreds of parsecs. Using the HST/ F 140 W image of the GRB field, we show the GRB host galaxy (with a possible afterglow contamination) as well as multiple objects within 2″ from the GRB position. We discuss the galaxy structure and kinematics that could explain our observations, also taking into account a tentative detection of Lyman- α emission at z = 6.3449 (∼1200 km s −1 from the GRB redshift in velocity space), and the observational properties of Lyman- α emitters at very high redshift. This study shows the amazing potential of GRBs to access detailed information on the properties (metal enrichment, gas kinematic, dust content, nucleosynthesis...) of very high-redshift galaxies, independently of the galaxy luminosity. Deep spectroscopic observations with VLT/MUSE and JWST will offer the unique possibility of combining the information presented in this paper with the properties of the ionized gas, with the goal of better understanding how galaxies in the reionization era form and evolve.
Publisher: Oxford University Press (OUP)
Date: 16-03-2011
Publisher: Oxford University Press (OUP)
Date: 02-11-2017
Publisher: Oxford University Press (OUP)
Date: 04-11-2019
Abstract: We present the design, methods, and first results of the MUSE Analysis of Gas around Galaxies (MAGG) survey, a large programme on the Multi-Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT), which targets 28 z & 3.2 quasars to investigate the connection between optically thick gas and galaxies at z ∼ 3–4. MAGG maps the environment of 52 strong absorption line systems at z ≳ 3, providing the first statistical s le of galaxies associated with gas-rich structures in the early Universe. In this paper, we study the galaxy population around a very metal poor gas cloud at z ≈ 3.53 towards the quasar J124957.23−015928.8. We detect three Lyα emitters within $\\lesssim 200~\\rm km~s^{-1}$ of the cloud redshift, at projected separations $\\lesssim 185~\\rm ~kpc$ (physical). The presence of star-forming galaxies near a very metal-poor cloud indicates that metal enrichment is still spatially inhomogeneous at this redshift. Based on its very low metallicity and the presence of nearby galaxies, we propose that the most likely scenario for this Lyman Limit System (LLS) is that it lies within a filament which may be accreting on to a nearby galaxy. Taken together with the small number of other LLSs studied with MUSE, the observations to date show a range of different environments near strong absorption systems. The full MAGG survey will significantly expand this s le and enable a statistical analysis of the link between gas and galaxies to pin down the origin of these erse environments at z ≈ 3–4.
Publisher: Oxford University Press (OUP)
Date: 24-09-2014
Publisher: American Astronomical Society
Date: 23-03-2018
Publisher: EDP Sciences
Date: 13-11-2012
Publisher: American Astronomical Society
Date: 02-2010
Publisher: American Physical Society (APS)
Date: 19-07-2017
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201832992
Abstract: Context . Absorbing galaxies are selected via the detection of characteristic absorption lines which their gas-rich media imprint in the spectra of distant light-beacons. The proximity of the typically faint foreground absorbing galaxies to bright background sources makes it challenging to robustly identify these in emission, and hence to characterise their relation to the general galaxy population. Aims . We search for emission to confirm and characterise ten galaxies hosting d ed, metal-rich quasar absorbers at redshift z 1. Methods . We identified the absorbing galaxies by matching spectroscopic absorption -and emission redshifts and from projected separations. Combining emission-line diagnostics with existing absorption spectroscopy and photometry of quasar-fields hosting metal-rich, d ed absorbers, we compare our new detections with reference s les and place them on scaling relations. Results . We spectroscopically confirm seven galaxies harbouring d ed absorbers (a 70% success-rate). Our results conform to the emerging picture that neutral gas on scales of tens of kpc in galaxies is what causes the characteristic H I absorption. Our key results are: (I) Absorbing galaxies with log 10 [ M ⋆ ,( M ⊙ )] ≳ 10 have star formation rates that are lower than predicted for the main sequence of star formation. (II) The distribution of impact parameter with H I column density and with absorption-metallicity for absorbing galaxies at z ∼ 2–3 extends to z ∼ 0.7 and to lower H I column densities. (III) A robust mean metallicity gradient of ⟨Γ⟩ = −0.022 ± 0.001 dex kpc −1 . (IV) By correcting absorption metallicities for ⟨Γ⟩ and imposing a truncation-radius at 12 kpc, absorbing galaxies fall on top of predicted mass-metallicity relations, with a statistically significant decrease in scatter.
Publisher: American Astronomical Society
Date: 29-03-2019
Publisher: EDP Sciences
Date: 03-2002
Publisher: Oxford University Press (OUP)
Date: 12-06-2021
Abstract: We report on the stellar content, half-light radii and star formation rates of a s le of 10 known high-redshift (z ≳ 2) galaxies selected on strong neutral hydrogen (H i) absorption ($\\log ({\\rm N_{H\\, \\rm {I}}\\: /\\: cm}^{-2})\\,\\gt\\, 19$) towards background quasars. We use observations from the Hubble Space Telescope Wide Field Camera 3 in three broad-band filters to study the spectral energy distribution (SED) of the galaxies. Using careful quasar point spread function subtraction, we study their galactic environments, and perform the first systematic morphological characterization of such absorption-selected galaxies at high redshifts. Our analysis reveals complex, irregular hosts with multiple star-forming clumps. At a spatial s ling of 0.067 arcsec per pixel (corresponding to 0.55 kpc at the median redshift of our s le), 40 per cent of our s le requires multiple Sérsic components for an accurate modelling of the observed light distributions. Placed on the mass–size relation and the ‘main sequence’ of star-forming galaxies, we find that absorption-selected galaxies at high redshift extend known relations determined from deep luminosity-selected surveys to an order of magnitude lower stellar mass, with objects primarily composed of star-forming, late-type galaxies. We measure half-light radii in the range r1/2 ∼ 0.4 to 2.6 kpc based on the reddest band (F160W) to trace the oldest stellar populations, and stellar masses in the range log (M⋆/M⊙) ∼ 8 to 10 derived from fits to the broad-band SED. Spectroscopic and SED-based star formation rates are broadly consistent, and lie in the range $\\log (\\mathrm{SFR}/{\\rm M}_{\\odot }\\, {\\rm yr}^{-1}) \\sim 0.0$ to 1.7.
Publisher: EDP Sciences
Date: 21-07-2011
Publisher: American Astronomical Society
Date: 27-03-2018
Publisher: American Astronomical Society
Date: 18-09-2020
Publisher: American Astronomical Society
Date: 18-06-2018
Publisher: Oxford University Press (OUP)
Date: 14-03-2019
DOI: 10.1093/MNRAS/STZ735
Abstract: We report Giant Metrewave Radio Telescope (GMRT), Very Large Telescope (VLT), and Spitzer Space Telescope observations of ESO 184−G82, the host galaxy of GRB 980425/SN 1998bw, that yield evidence of a companion dwarf galaxy at a projected distance of 13 kpc. The companion, hereafter GALJ193510-524947, is a gas-rich, star-forming galaxy with a star formation rate of $\\rm 0.004\\, M_{\\odot }\\, yr^{-1}$, a gas mass of $10^{7.1\\pm 0.1} \\, \\mathrm{M}_{\\odot}$, and a stellar mass of $10^{7.0\\pm 0.3} \\, \\mathrm{M}_{\\odot}$. The interaction between ESO 184−G82 and GALJ193510-524947 is evident from the extended gaseous structure between the two galaxies in the GMRT H i 21 cm map. We find a ring of high column density H i gas, passing through the actively star-forming regions of ESO 184−G82 and the GRB location. This ring lends support to the picture in which ESO 184−G82 is interacting with GALJ193510-524947. The massive stars in GALJ193510-524947 have similar ages to those in star-forming regions in ESO 184−G82, also suggesting that the interaction may have triggered star formation in both galaxies. The gas and star formation properties of ESO 184−G82 favour a head-on collision with GALJ193510-524947 rather than a classical tidal interaction. We perform state-of-the-art simulations of dwarf–dwarf mergers and confirm that the observed properties of ESO 184−G82 can be reproduced by collision with a small companion galaxy. This is a very clear case of interaction in a gamma-ray burst host galaxy and of interaction-driven star formation giving rise to a gamma-ray burst in a dense environment.
No related grants have been discovered for Lise Christensen.