99 research outputs found
QSO Museum I: A sample of 61 extended Ly α-emission nebulae surrounding z ∼ 3 quasars
The WISSH quasars project: VIII. Outflows and metals in the circum-galactic medium around the hyper-luminous z 3c 3.6 quasar J1538+08
Context. In recent years, Ly\u3b1 nebulae have been routinely detected around high redshift, radio-quiet quasars thanks to the advent of the highly sensitive integral field spectrographs. Constraining the physical properties of the Ly\u3b1 nebulae is crucial for a full understanding of the circum-galactic medium (CGM). The CGM acts both as a repository for intergalactic and galactic baryons as well as a venue of feeding and feedback processes. The most luminous quasars are privileged test-beds to study these processes, given their large ionising fluxes and dense CGM environments in which they are expected to be embedded. Aims. We aim to characterise the rest-frame ultraviolet (UV) emission lines in the CGM around a hyper-luminous, broad emission line, radio-quiet quasar at z 3c 3.6, which exhibits powerful outflows at both nuclear and host galaxy scales. Methods. We analyse VLT/MUSE observations of the quasar J1538+08 (Lbol = 6
7 1047 erg s-1), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content. Results. We report the discovery of a very luminous ( 3c2
7 1044 erg s-1), giant Ly\u3b1 nebula and a likely associated extended (75 kpc) CIV nebula. The Ly\u3b1 nebula emission exhibits moderate blueshift ( 3c440 km s-1) compared to the quasar systemic redshift and a large average velocity dispersion (\u3c3\u304v 3c700 km s-1) across the nebula, while the CIV nebula shows average velocity dispersion of \u3c3\u304v 3c350 km s-1. The Ly\u3b1 line profile exhibits a significant asymmetry towards negative velocity values at 20-30 kpc south of the quasar and is well parametrised by the following two Gaussian components: a narrow (\u3c3 3c 470 km s-1) systemic one plus a broad (\u3c3 3c 1200 km s-1), blueshifted ( 3c1500 km s-1) one. Conclusions. Our analysis of the MUSE observation of J1538+08 reveals metal-enriched CGM around this hyper-luminous quasar. Furthermore, our detection of blueshifted emission in the emission profile of the Ly\u3b1 nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). II. Constraints on star formation in ram-pressure stripped gas
Context: Several galaxies in the Virgo cluster are known to have large HI gas
tails related to a recent ram-pressure stripping event. The Virgo cluster has
been extensively observed at 1539 A in the far-ultraviolet for the GALEX
Ultraviolet Virgo Cluster Survey (GUViCS), and in the optical for the Next
Generation Virgo Survey (NGVS), allowing a study of the stellar emission
potentially associated with the gas tails of 8 cluster members. On the
theoretical side, models of ram-pressure stripping events have started to
include the physics of star formation. Aim: We aim to provide quantitative
constraints on the amount of star formation taking place in the ram-pressure
stripped gas, mainly on the basis of the far-UV emission found in the GUViCS
images in relation with the gas content of the tails. Methods: We have
performed three comparisons of the young stars emission with the gas column
density: visual, pixel-by-pixel and global. We have compared our results to
other observational and theoretical studies. Results: We find that the level of
star formation taking place in the gas stripped from galaxies by ram-pressure
is low with respect to the available amount of gas. Star formation is lower by
at least a factor 10 compared to the predictions of the Schmidt Law as
determined in regular spiral galaxy disks. It is also lower than measured in
dwarfs galaxies and the outer regions of spirals, and than predicted by some
numerical simulations. We provide constraints on the star formation efficiency
in the ram-pressure stripped gas tails, and compare these with current models.Comment: Accepted in A&A, 17 pages (including the appendix and "on-line"
figures of the paper
Gas Accretion and Giant Lyman-alpha Nebulae
Several decades of observations and discoveries have shown that high-redshift
AGN and massive galaxies are often surrounded by giant Lyman-alpha nebulae
extending in some cases up to 500 kpc in size. In this review, I discuss the
properties of the such nebulae discovered at z>2 and their connection with gas
flows in and around the galaxies and their halos. In particular, I show how
current observations are used to constrain the physical properties and origin
of the emitting gas in terms of the Lyman-alpha photon production processes and
kinematical signatures. These studies suggest that recombination radiation is
the most viable scenario to explain the observed Lyman-alpha luminosities and
Surface Brightness for the large majority of the nebulae and imply that a
significant amount of dense, ionized and cold clumps should be present within
and around the halos of massive galaxies. Spectroscopic studies suggest that,
among the giant Lyman-alpha nebulae, the one associated with radio-loud AGN
should have kinematics dominated by strong, ionized outflows within at least
the inner 30-50 kpc. Radio-quiet nebulae instead present more quiescent
kinematics compatible with stationary situation and, in some cases, suggestive
of rotating structures. However, definitive evidences for accretion onto
galaxies of the gas associated with the giant Lyman-alpha emission are not
unambiguously detected yet. Deep surveys currently ongoing using other bright,
non-resonant lines such as Hydrogen H-alpha and HeII1640 will be crucial to
search for clearer signatures of cosmological gas accretion onto galaxies and
AGN.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dave', to be published by
Springe
The Quasar Feedback Survey: characterising CO excitation in quasar host galaxies
We present a comprehensive study of the molecular gas properties of 17 Type 2
quasars at 10^{42.1}\rm ergs^{-1}_{up}r_{21}_{21}_{CO(2-1)}_{CO(1-0)}r_{21}r_{21}\sim_{21}\simr_{21} values, for the 7
targets with the required data we find low excitation in CO(6-5) & CO(7-6)
(r_{61}r_{62}$ < 0.6 in all but one target), unlike high redshift
quasars in the literature, which are far more luminous and show higher line
ratios. The ionised gas traced by [OIII] exhibit systematically higher
velocities than the molecular gas traced by CO. We conclude that any effects of
quasar feedback (e.g. via outflows and radio jets) do not have a significant
instantaneous impact on the global molecular gas content and excitation and we
suggest that it only occurs on more localised scales.Comment: 32 pages (20 in the main body of the paper and 12 in the appendix),
28 figures (10 in main body of paper and 18 in appendix) Accepted for
publication in MNRAS. Data available at
https://doi.org/10.25405/data.ncl.2431250
Quasar feedback survey: molecular gas affected by central outflows and by ∼10-kpc radio lobes reveal dual feedback effects in ‘radio quiet’ quasars
SUPER VI. A giant molecular halo around a z∼2 quasar
We present the discovery of copious molecular gas in the halo of cid_346, a z = 2.2 quasar studied as part of the SINFONI survey for Unveiling the Physics and Effect of Radiative feedback (SUPER). New Atacama Compact Array (ACA) CO(3−2) observations detect a much higher flux (by a factor of 14 ± 5) than measured on kiloparsec scales (r ≲ 8 kpc) using previous snapshot Atacama Large Millimeter/submillimeter Array data. Such additional CO(3−2) emission traces a structure that extends out to r ∼ 200 kpc in projected size, as inferred through direct imaging and confirmed by an analysis of the uv visibilities. This is the most extended molecular circumgalactic medium (CGM) reservoir that has ever been mapped. It shows complex kinematics, with an overall broad line profile (FWHM = 1000 km s−1) that is skewed towards redshifted velocities up to at least v ∼ 1000 km s−1. Using the optically thin assumption, we estimate a strict lower limit for the total molecular CGM mass observed by ACA of MmolCGM > 1010 M⊙. There is however room for up to MmolCGM ∼ 1.7 × 1012 M⊙, once optically thick CO emission with αCO = 3.6 M⊙ (K km s−1 pc2)−1 and L′CO(3−2)/L′CO(1−0) = 0.5 are assumed. Since cid_346 hosts quasar-driven ionised outflows and since there is no evidence of merging companions or an overdensity, we suggest that outflows may have played a crucial rule in seeding metal-enriched, dense gas on halo scales. However, the origin of such an extended molecular CGM remains unclear
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