Search

We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM–Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at z ≃ 3.23, separated by ∼500 kpc in projection. Both quasars are embedded within extended Lyα nebulae (⁠|${\gtrsim}100\,{\rm kpc}$| at a surface brightness flux level of ≈6 × 10−19  |${\rm erg\,s^{-1}\,cm^{-2}\,arcsec^{-2}}$|⁠), whose elongated morphology is suggestive of an extended filament connecting the quasar haloes. The new X-ray observations presented here allow us to characterize the physical properties (e.g. X-ray slope, luminosities, gas column densities) in the innermost region of the MUDF quasars. We find that both quasars are X-ray underluminous compared to objects at similar ultraviolet luminosities. Based on our X-ray spectral analysis, absorbing columns of N H(z) ≳ 1023 cm−2 appear unlikely therefore such a weakness is possibly intrinsic. When also including literature data, we do not observe any detectable trend between the area of the nebulae and nuclear luminosities at both the rest-frame 2 keV and 2500 Å. The area is also not correlated with the X-ray photon index nor with the integrated band flux in the hard band (2–10 keV). We also do not find any trend between the extended Lyα emission of the nebulae and the nuclear X-ray luminosity. Finally, the properties of the MUDF quasars' nebulae are consistent with the observed relation between the Lyα integrated luminosity of the nebulae and their area. Our results suggest that the quasar ionization power is not a strong driver of the morphology and size of the nebulae. [ABSTRACT FROM AUTHOR]

Lyman α (Lyα) is now routinely used as a tool for studying high-redshift galaxies, and its resonant nature means it can trace neutral hydrogen around star-forming galaxies. Integral field spectrograph measurements of high-redshift Lyα emitters indicate that significant extended Lyα halo emission is ubiquitous around such objects. We present a sample of redshift 0.23 to 0.31 galaxies observed with the Hubble Space Telescope selected to match the star formation properties of high- z samples while optimizing the observations for detection of low surface brightness Lyα emission. The Lyα escape fractions range between 0.7 and 37 per cent, and we detect extended Lyα emission around six out of seven targets. We find Lyα halo to UV scale length ratios around 6:1, which is marginally lower than high-redshift observations, and halo flux fractions between 60 and 85 per cent – consistent with high-redshift observations – when using comparable methods. However, our targets show additional extended stellar UV emission: we parametrize this with a new double exponential model. We find that this parametrization does not strongly affect the observed Lyα halo fractions. We find that deeper Hα data would be required to firmly determine the origin of Lyα halo emission; however, there are indications that Hα is more extended than the central FUV profile, potentially indicating conditions favourable for the escape of ionizing radiation. We discuss our results in the context of high-redshift galaxies, cosmological simulations, evolutionary studies of the circumgalactic medium in emission, and the emission of ionizing radiation. [ABSTRACT FROM AUTHOR]

We outline theoretical predictions for extended emission from Mg  ii , tracing cool ∼104 K gas in the circumgalactic medium (CGM) of star-forming galaxies in the high-resolution TNG50 cosmological magnetohydrodynamical simulation. We synthesize surface brightness maps of this strong rest-frame ultraviolet metal emission doublet (λλ2796, 2803), adopting the assumption that the resonant scattering of Mg  ii can be neglected and connecting to recent and upcoming observations with the Keck/KCWI, VLT/MUSE, and BlueMUSE optical integral field unit spectrographs. Studying galaxies with stellar masses 7.5 < log (M ⋆/ M ⊙) < 11 at redshifts z = 0.3, 0.7, 1, and 2 we find that extended Mg  ii haloes in emission, similar to their Ly α counterparts, are ubiquitous across the galaxy population. Median surface brightness profiles exceed 10−19 erg s−1 cm−2 arcsec−2 in the central |$\sim \,$| 10 s of kpc, and total halo Mg  ii luminosity increases with mass for star-forming galaxies, reaching 1040 erg s−1 for M ⋆ ∼ 109.5 M⊙. Mg  ii halo sizes increase from a few kpc to ≳ 20 kpc at the highest masses, and sizes are larger for haloes in denser environments. Mg  ii haloes are highly structured, clumpy, and asymmetric, with isophotal axial ratio increasing with galaxy mass. Similarly, the amount and distribution of Mg  ii emission depends on the star formation activity of the central galaxy. Kinematically, inflowing versus outflowing gas dominates the Mg  ii luminosity at high and low galaxy masses, respectively, although the majority of Mg  ii halo emission at z ∼ 0.7 traces near-equilibrium fountain flows and gas with non-negligible rotational support, rather than rapidly outflowing galactic winds. [ABSTRACT FROM AUTHOR]

Dust is an essential ingredient of galaxies, determining the physical and chemical conditions in the interstellar medium. Several complementary observational evidences indicate that the cosmic dust mass density significantly drops from redshift z = 1 to z = 0. Clearly, and for the first time during cosmic evolution, dust must be destroyed more rapidly than it is formed. By considering the dust production/destruction processes acting in this cosmic time lapse, we find that the drop can be explained if dust is mainly destroyed by astration (49 per cent contribution in the fiducial case) and supernova (SN) shocks within galaxies (42 per cent). Our results further imply that on average each SN destroys only |$M_{\mathrm{ d},\mathrm{ sn}} =0.45\, \mathrm{ M}_\odot$| of dust, i.e. 5–10 times less than usually assumed, with a hard upper limit of M d,sn < 3.0 M⊙ set by the available metal budget and maximal grain growth. The lower efficiency might be explained by effective shielding of dust against shock processing in pre-SN wind shells. [ABSTRACT FROM AUTHOR]

We present a study of the galaxy environment of nine strong H  i  + C  iv absorption line systems (16.2 < log(N (HI)) < 21.2) spanning a wide range in metallicity at z ∼ 4−5, using MUSE integral field and X-Shooter spectroscopic data collected in a z ≈ 5.26 quasar field. We identify galaxies within a 250 kpc and ±1000 km s−1 window for six out of the nine absorption systems, with two of the absorption line systems showing multiple associated galaxies within the MUSE field of view. The space density of Ly α emitting galaxies (LAEs) around the H  i and C  iv systems is ≈10−20 times the average sky density of LAEs given the flux limit of our survey, showing a clear correlation between the absorption and galaxy populations. Further, we find that the strongest C  iv systems in our sample are those that are most closely aligned with galaxies in velocity space, i.e. within velocities of ±500 km s−1. The two most metal-poor systems lie in the most dense galaxy environments, implying we are potentially tracing gas that is infalling for the first time into star-forming groups at high redshift. Finally, we detect an extended Ly α nebula around the z ≈ 5.26 quasar, which extends up to ≈50 kpc at the surface brightness limit of 3.8 × 10−18 erg s−1 cm−2 arcsec−2. After scaling for surface brightness dimming, we find that this nebula is centrally brighter, having a steeper radial profile than the average for nebulae studied at z ∼ 3 and is consistent with the mild redshift evolution seen from z ≈ 2. [ABSTRACT FROM AUTHOR]

We present the goals, design, and first results of the MUSE Ultra Deep Field (MUDF) survey, a large programme using the Multi Unit Spectroscopic Explorer (MUSE) instrument at the ESO Very Large Telescope. The MUDF survey is collecting ≈150 h on-source of integral field optical spectroscopy in a 1.5 × 1.2 arcmin2 region which hosts several astrophysical structures along the line of sight, including two bright z ≈ 3.2 quasars with close separation (≈500 kpc). Following the description of the data reduction procedures, we present the analysis of the galaxy environment and gaseous properties of seven groups detected at redshifts 0.5 < z < 1.5, spanning a large dynamic range in halo mass, |$\log (M_h/\rm {M_\odot }) \approx 11 - 13.5$|⁠. For four of the groups, we find associated Mg  ii absorbers tracing cool gas in high-resolution spectroscopy of the two quasars, including one case of correlated absorption in both sightlines at distance ≈480 kpc. The absorption strength associated with the groups is higher than what has been reported for more isolated galaxies of comparable mass and impact parameters. We do not find evidence for widespread cool gas giving rise to strong absorption within these groups. Combining these results with the distribution of neutral and ionized gas seen in emission in lower redshift groups, we conclude that gravitational interactions in the group environment strip gas from the galaxy haloes into the intragroup medium, boosting the cross-section of cool gas and leading to the high fraction of strong Mg  ii absorbers that we detect. [ABSTRACT FROM AUTHOR]

We present VLT-SINFONI near infra-red spectra of 26 new heavily reddened quasar candidates selected from the UKIDSS-LAS, VISTA VHS, and VIKING imaging surveys. This new sample extends our reddened quasar search to both brighter and fainter luminosities. 25 of the 26 candidates are confirmed to be broad line quasars with redshifts 0.7 < z < 2.6 and dust extinctions 0.5 < E (B − V) < 3.0. Combining with previously identified samples, we study the H α, H β, and [O  iii ] emission line properties in 22 heavily reddened quasars with L bol ≈ 1047 erg s−1 and z > 2. We present the first comparison of the [O  iii ] line properties in high luminosity reddened quasars to a large sample of 111 unobscured quasars in the same luminosity and redshift range. Broad wings extending to velocities of 2500 km s−1 are seen in the [O  iii ] emission line profiles of our reddened quasars, suggesting that strong outflows are affecting the ionized gas kinematics. However, we find no significant difference between the kinematics of the [O  iii ] emission in reddened and unobscured quasars when the two samples are matched in luminosity and redshift. Our results are consistent with a model where quasar-driven outflows persist for some time after the obscuring dust has been cleared from along the line of sight. Assuming the amount of ionized gas in reddened and unobscured quasars is similar, we use the equivalent width distribution of the [O  iii ] emission to constrain the location of the obscuring dust in our reddened quasars. We find that the dust is most likely to be located on galactic scales, outside the [O  iii ] emitting region. [ABSTRACT FROM AUTHOR]

We present first results from Multi Unit Spectroscopic Explorer (MUSE) observations at the Very Large Telescope in the MUSE Ultra Deep Field (MUDF), a ≈1.2 × 1.4 arcmin2 region for which we are collecting ≈200 hours of integral field spectroscopy. The ≈40-h observation completed to date reveals the presence of a group of three Lyα nebulae associated with a bright quasar pair at |$z$|  ≃ 3.23 with projected separation of |${\approx } 500\rm ~kpc$|⁠. Two of the nebulae are physically associated with the quasars which are likely powering the Lyα emission, and extend for |${\gtrsim } 100~\rm kpc$| at a surface brightness level of ≈6 × 10−19  |$\rm erg\,s^{-1}\,cm^{-2}\,arcsec^{-2}$|⁠. A third smaller (≈35 kpc) nebula lies at a velocity offset of ≈1550 km s−1. Despite their clustered nature, the two large nebulae have properties similar to those observed in isolated quasars and exhibit no sharp decline in flux at the current depth, suggesting an even more extended distribution of gas around the quasars. We interpret the shape and the alignment of the two brighter nebulae as suggestive of the presence of an extended structure connecting the two quasar host galaxies, as seen for massive galaxies forming within gas-rich filaments in cosmological simulations. [ABSTRACT FROM AUTHOR]

We present initial results of a new, systematic search for massive star formation in the host galaxies of the most luminous and probably most massive z&gsim;4 radio-quiet quasars (M[sub B]≤-27.5; νL[sub ν](1450 Å)>10[sup 13] L[sub ⊙]). The survey, undertaken at 850 μm using SCUBA at the James Clerk Maxwell Telescope (JCMT), has a target sensitivity limit of 3σ∼10 mJy, set to identify sources suitable for detailed follow-up, e.g. continuum mapping and molecular line diagnostics. A total of 38 z&gsim;4 radio-quiet quasars have been observed at 850 μm, of which eight were detected (>3σ) with S[sub 850μm]&gsim;10 mJy (submillimetre-loud). The new detections almost triple the number of optically selected, submillimetre-loud z&gsim;4 radio-quiet quasars known to date. We include a detailed description of how our quasar sample is defined in terms of radio and optical properties. As a by-product of our selection procedure, we have identified 17 radio-loud quasars with z&gsim;4. There is no strong evidence for trends in either detectability or 850-μm flux with absolute magnitude, M[sub B]. We find that the weighted mean flux of the undetected sources is 2.0±0.6 mJy, consistent with an earlier estimate of ∼3 mJy based on more sensitive observations of a sample z&gsim;4 radio-quiet quasars. This corresponds to an inferred star formation rate of ∼1000 M[sub ⊙] yr[sup -1], similar to Arp220. The typical star formation time-scale for the submillimetre-bright sources is ∼1 Gyr, 10 times longer than the typical accretion-driven e-folding time-scale of ∼5×10[sup 7] yr. Our 850-μm detection of the z=4.4 quasar PSS J1048+4407, when analysed in conjunction with 1.2-mm single-dish and interferometric observations, suggests that this source is resolved on angular scales of 1–2 arcsec (6–12 kpc). In addition, we present a new optical spectrum of this source, identifying it as a broad absorption line (BAL) quasar. The new redshift is outside that covered in a recent CO line search, highlighting the need for accurate redshifts for the observation and interpretation of high-redshift line studies. [ABSTRACT FROM AUTHOR]