TY  - JOUR
A1  - Davidzon, Iary
A1  - Ilbert, Olivier
A1  - Faisst, Andreas L.
A1  - Sparre, Martin
A1  - Capak, Peter L.
T1  - An Alternate Approach to Measure Specific Star Formation Rates at 2 < z < 7
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We trace the specific star formation rate (sSFR) of massive star-forming galaxies (greater than or similar to 10(10)M(circle dot)) from z similar to 2 to 7. Our method is substantially different from previous analyses, as it does not rely on direct estimates of star formation rate, but on the differential evolution of the galaxy stellar mass function (SMF). We show the reliability of this approach by means of semianalytical and hydrodynamical cosmological simulations. We then apply it to real data, using the SMFs derived in the COSMOS and CANDELS fields. We find that the sSFR is proportional to (1 + z)(1.1) (+/-) (0.2) at z > 2, in agreement with other observations but in tension with the steeper evolution predicted by simulations from z similar to 4 to 2. We investigate the impact of several sources of observational bias, which, however, cannot account for this discrepancy. Although the SMF of high-redshift galaxies is still affected by significant errors, we show that future large-area surveys will substantially reduce them, making our method an effective tool to probe the massive end of the main sequence of star-forming galaxies.
KW  - galaxies: evolution
KW  - galaxies: high-redshift
KW  - galaxies: star formation
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aaa19e
SN  - 0004-637X
SN  - 1538-4357
VL  - 852
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Husemann, Bernd
A1  - Worseck, Gabor
A1  - Battaia, Fabrizio Arrigoni
A1  - Shanks, T.
T1  - Discovery of a dual AGN at z similar or equal to 3.3 with 20 kpc separation
JF  - Astronomy and astrophysics : an international weekly journal
N2  - A prediction of the current paradigm of the hierarchical assembly of galaxies is the presence of supermassive dual black holes at separations of a few kpc or less. In this context, we report the detection of a narrow-line emitter within the extended Ly alpha nebula (similar to 120 kpc diameter) of the luminous radio-quiet quasi-stellar object (QSO) LBQS 0302 0019 at z = 3 : 286. We identify several high-ionization narrow emission lines (He II, C IV, C III) associated with this point-like source, which we have named "Jil", which is only similar to 20 kpc (2 : 0 0 9) away from the QSO in projection. Emission-line diagnostics confirm that the source is likely powered by photoionization of an obscured active galactic nucleus (AGN) three orders of magnitude fainter than the QSO. The system represents the tightest unobscured/obscured dual AGN currently known at z > 3, highlighting the power of MUSE to detect these elusive systems.
KW  - Techniques: imaging spectroscopy
KW  - Ultraviolet: ISM
KW  - galaxies: high-redshift
KW  - quasars: individual: LBQS 0302-0019
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201732457
SN  - 1432-0746
VL  - 610
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Marino, Raffaella Anna
A1  - Cantalupo, Sebastiano
A1  - Lilly, Simon J.
A1  - Gallego, Sofia G.
A1  - Straka, Lorrie A.
A1  - Borisova, Elena
A1  - Pezzulli, Gabriele
A1  - Bacon, Roland
A1  - Brinchmann, Jarle
A1  - Carollo, C. Marcella
A1  - Caruana, Joseph
A1  - Conseil, Simon
A1  - Contini, Thierry
A1  - Diener, Catrina
A1  - Finley, Hayley
A1  - Inami, Hanae
A1  - Leclercq, Floriane
A1  - Muzahid, Sowgat
A1  - Richard, Johan
A1  - Schaye, Joop
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - Dark Galaxy Candidates at Redshift similar to 3.5 Detected with MUSE
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z > 3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly alpha sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly alpha luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240 angstrom that are the best candidates for dark galaxies in our survey at z > 3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z approximate to 2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t - 60 Myr on the quasar lifetime.
KW  - galaxies: formation
KW  - galaxies: high-redshift
KW  - galaxies: star formation
KW  - intergalactic medium
KW  - quasars: emission lines
KW  - quasars: general
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aab6aa
SN  - 0004-637X
SN  - 1538-4357
VL  - 859
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Adam, Remi
A1  - Aharonian, Felix A.
A1  - Benkhali, Faical Ait
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arakawa, Masanori
A1  - Arcaro, C
A1  - Armand, Catherine
A1  - Armstrong, T.
A1  - Egberts, Kathrin
T1  - Very high energy γ-ray emission from two blazars of unknown redshift and upper limits on their distance
JF  - Monthly Notices of the Royal Astronomical Society
N2  - We report on the detection of very high energy (VHE; E > 100 GeV) gamma-ray emission from the BL Lac objects KUV 00311-1938 and PKS 1440-389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi/LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi/LAT spectrum towards the VHE gamma-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311-1938 of z < 0.98 and of PKS 1440-389 of z < 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311-1938 is constrained to 0.51 <= z < 0.98 and of PKS 1440-389 to 0.14 (sic) z < 0.53.
KW  - BL Lacertae objects: individual
KW  - galaxies: high-redshift
KW  - gamma-rays: general
KW  - Resolved and unresolved sources as a function of wavelength
Y1  - 2020
VL  - 494
IS  - 4
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Schaerer, Daniel
A1  - Izotov, Yuri I.
A1  - Nakajima, K.
A1  - Worseck, Gabor
A1  - Chisholm, J.
A1  - Verhamme, A.
A1  - Thuan, T. X.
A1  - de Barros, S.
T1  - Intense C III] lambda lambda 1907,1909 emission from a strong Lyman continuum emitting galaxy
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum (LyC) emitter at low redshift - the compact, low-metallicity, star-forming galaxy J1154+2443 - with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Ly alpha and C III] lambda 1909 emission, as well as O III] lambda 1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(C III]) = 11.7 +/- 2.9 angstrom rest-frame), although their equivalent widths should be reduced due to the loss of ionizing photons. The intrinsic ionizing photon production efficiency of J1154+2443 is high, log(xi(0)(ion)) = 25.56 erg(-1) Hz, comparable to that of other recently discovered z similar to 0.3-0.4 LyC emitters. Combining our measurements and earlier determinations from the literature, we find a trend of increasing xi(0)(ion) with increasing C III] lambda 1909 equivalent width, which can be understood by a combination of decreasing stellar population age and metallicity. Simple ionization and density-bounded photoionization models can explain the main observational features including the UV spectrum of J1154+2443.
KW  - galaxies: starburst
KW  - galaxies: high-redshift
KW  - dark ages, reionization, first stars
KW  - ultraviolet: galaxies
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201833823
SN  - 1432-0746
VL  - 616
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Perrotta, S.
A1  - Hamann, F.
A1  - Cristiani, S.
A1  - Prochaska, J. X.
A1  - Ellison, Sara L.
A1  - Lopez, S.
A1  - Cupani, G.
A1  - Becker, G.
A1  - Berg, T. A. M.
A1  - Christensen, Lise
A1  - Denney, K. D.
A1  - Worseck, Gábor
T1  - Hunting for metals using XQ-100 Legacy Survey composite spectra
JF  - Monthly notices of the Royal Astronomical Society
N2  - We investigate the NV absorption signal along the line of sight of background quasars, in order to test the robustness of the use of this ion as the criterion to select intrinsic (i.e. physically related to the quasar host galaxy) narrow absorption lines (NALs). We build composite spectra from a sample of similar to 1000 CIV absorbers, covering the redshift range 2.55 < z < 4.73, identified in 100 individual sight lines from the XQ-100 Legacy Survey. We detect a statistically significant NV absorption signal only within 5000 km s(-1) of the systemic redshift, z(em). This absorption trough is similar to 15 sigma when only CIV systems with N(CIV) > 10(14) cm(-2) are included in the composite spectrum. This result confirms that NV offers an excellent statistical tool to identify intrinsic systems. We exploit stacks of 11 different ions to show that the gas in proximity to a quasar exhibits a considerably different ionization state with respect to gas in the transverse direction and intervening gas at large velocity separations from the continuum source. Indeed, we find a dearth of cool gas, as traced by low-ionization species and in particular by MgII, in the proximity of the quasar. We compare our findings with the predictions given by a range of CLOUDY ionization models and find that they can be naturally explained by ionization effects of the quasar.
KW  - galaxies: high-redshift
KW  - (galaxies:) intergalactic medium
KW  - (galaxies:) quasars: absorption lines
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty2205
SN  - 0035-8711
SN  - 1365-2966
VL  - 481
IS  - 1
SP  - 105
EP  - 121
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Selsing, Jonatan
A1  - Malesani, D.
A1  - Goldoni, P.
A1  - Fynbo, Johan
A1  - Krühler, T.
A1  - Antonelli, L. A.
A1  - Arabsalmani, M.
A1  - Bolmer, J.
A1  - Cano, Z.
A1  - Christensen, L.
A1  - Covino, S.
A1  - De Cia, A.
A1  - de Ugarte Postigo, A.
A1  - Flores, H.
A1  - Fliis, M.
A1  - Gomboc, A.
A1  - Greiner, J.
A1  - Groot, P.
A1  - Hammer, F.
A1  - Hartoog, O. E.
A1  - Heintz, K. E.
A1  - Hjorth, J.
A1  - Jakobsson, P.
A1  - Japelj, J.
A1  - Kann, D. A.
A1  - Kaper, L.
A1  - Ledoux, C.
A1  - Leloudas, G.
A1  - Levan, A. J.
A1  - Maiorano, E.
A1  - Melandri, A.
A1  - Milvang-Jensen, B.
A1  - Palazzi, E.
A1  - Palmerio, J. T.
A1  - Perley, D. A.
A1  - Pian, E.
A1  - Piranomonte, S.
A1  - Pugliese, G.
A1  - Sanchez-Ramirez, R.
A1  - Savaglio, S.
A1  - Schady, P.
A1  - Schulze, S.
A1  - Sollerman, J.
A1  - Sparre, Martin
A1  - Tagliaferri, G.
A1  - Tanvir, N. R.
A1  - Thone, C. C.
A1  - Vergani, S. D.
A1  - Vreeswijk, P.
A1  - Watson, D.
A1  - Wiersema, K.
A1  - Wijers, R.
A1  - Xu, D.
A1  - Zafar, T.
T1  - The X-shooter GRB afterglow legacy sample (XS-GRB)
JF  - Astronomy and astrophysics : an international weekly journal
N2  - In this work we present spectra of all gamma-ray burst (GRB) afterglows that have been promptly observed with the X-shooter spectrograph until 31/03/2017. In total, we have obtained spectroscopic observations of 103 individual GRBs observed within 48 hours of the GRB trigger. Redshifts have been measured for 97 per cent of these, covering a redshift range from 0.059 to 7.84. Based on a set of observational selection criteria that minimise biases with regards to intrinsic properties of the GRBs, the follow-up effort has been focused on producing a homogeneously selected sample of 93 afterglow spectra for GRBs discovered by the Swift satellite. We here provide a public release of all the reduced spectra, including continuum estimates and telluric absorption corrections. For completeness, we also provide reductions for the 18 late-time observations of the underlying host galaxies. We provide an assessment of the degree of completeness with respect to the parent GRB population, in terms of the X-ray properties of the bursts in the sample and find that the sample presented here is representative of the full Swift sample. We have constrained the fraction of dark bursts to be <28 per cent and confirm previous results that higher optical darkness is correlated with increased X-ray absorption. For the 42 bursts for which it is possible, we have provided a measurement of the neutral hydrogen column density, increasing the total number of published HI column density measurements by similar to 33 per cent. This dataset provides a unique resource to study the ISM across cosmic time, from the local progenitor surroundings to the intervening Universe.
KW  - gamma-ray burst: general
KW  - galaxies: high-redshift
KW  - ISM: general
KW  - techniques: spectroscopic
KW  - catalogs
KW  - galaxies: star formation
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201832835
SN  - 1432-0746
SN  - 0004-6361
VL  - 623
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  - Wisotzki, Lutz
A1  - Bacon, Roland
A1  - Blaizot, J.
A1  - Brinchmann, Jarle
A1  - Herenz, Edmund Christian
A1  - Schaye, Joop
A1  - Bouche, Nicolas
A1  - Cantalupo, Sebastiano
A1  - Contini, Thierry
A1  - Carollo, C. M.
A1  - Caruana, Joseph
A1  - Courbot, J. -B.
A1  - Emsellem, E.
A1  - Kamann, S.
A1  - Kerutt, Josephine Victoria
A1  - Leclercq, F.
A1  - Lilly, S. J.
A1  - Patricio, V.
A1  - Sandin, C.
A1  - Steinmetz, Matthias
A1  - Straka, Lorrie A.
A1  - Urrutia, Tanya
A1  - Verhamme, A.
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
T1  - Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE
JF  - Science
N2  - We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1 sigma) of similar to 1 x 10(-19) erg s(-1) cm(-2) arcsec(-2) in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m(AB) greater than or similar to 27) galaxies. In most objects the Ly alpha emission is considerably more extended than the UV continuum light. While five of the faintest galaxies in the sample show no significantly detected Ly alpha haloes, the derived upper limits suggest that this is due to insufficient S/N. Ly alpha haloes therefore appear to be ubiquitous even for low-mass (similar to 10(8)-10(9) M-circle dot) star-forming galaxies at z > 3. We decompose the Ly alpha emission of each object into a compact component tracing the UV continuum and an extended halo component, and infer sizes and luminosities of the haloes. The extended Ly alpha emission approximately follows an exponential surface brightness distribution with a scale length of a few kpc. While these haloes are thus quite modest in terms of their absolute sizes, they are larger by a factor of 5-15 than the corresponding rest-frame UV continuum sources as seen by HST. They are also much more extended, by a factor similar to 5, than Ly alpha haloes around low-redshift star-forming galaxies. Between similar to 40% and greater than or similar to 90% of the observed Ly alpha flux comes from the extended halo component, with no obvious correlation of this fraction with either the absolute or the relative size of the Ly alpha halo. Our observations provide direct insights into the spatial distribution of at least partly neutral gas residing in the circumgalactic medium of low to intermediate mass galaxies at z > 3.
KW  - galaxies: high-redshift
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - cosmology: observations
KW  - intergalactic medium
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527384
SN  - 1432-0746
VL  - 587
PB  - EDP Sciences
CY  - Les Ulis
ER  -