Giant Lyα Nebula Research Articles

The WISSH quasars project

Context. In recent years, Lyα 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 Lyα 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 ∼ 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 × 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 (∼2 × 1044 erg s−1), giant Lyα nebula and a likely associated extended (75 kpc) CIV nebula. The Lyα nebula emission exhibits moderate blueshift (∼440 km s−1) compared to the quasar systemic redshift and a large average velocity dispersion (σ¯v ∼ 700 km s−1) across the nebula, while the CIV nebula shows average velocity dispersion of σ¯v ∼ 350 km s−1. The Lyα 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 (σ ∼ 470 km s−1) systemic one plus a broad (σ ∼ 1200 km s−1), blueshifted (∼1500 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 Lyα nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs.

A Giant Lyα Nebula and a Small-scale Clumpy Outflow in the System of the Exotic Quasar J0952+0114 Unveiled by MUSE∗

Abstract The well-known quasar SDSS J095253.83+011421.9 (J0952+0114) at z = 3.02 has one of the most peculiar spectra discovered so far, showing the presence of narrow Lyα and broad metal emission lines. Although recent studies have suggested that a proximate damped Lyα absorption (PDLA) system causes this peculiar spectrum, the origin of the gas associated with the PDLA is unknown. Here we report the results of observations with the Multi Unit Spectroscopic Explorer (MUSE) that reveal a new giant (≈100 physical kpc) Lyα nebula. The detailed analysis of the Lyα velocity, velocity dispersion, and surface brightness profiles suggests that the J0952+0114 Lyα nebula shares similar properties with other QSO nebulae previously detected with MUSE, implying that the PDLA in J0952+0144 is covering only a small fraction of the solid angle of the QSO emission. We also detected bright and spectrally narrow C iv λ1550 and He ii λ1640 extended emission around J0952+0114 with velocity centroids similar to the peak of the extended and central narrow Lyα emission. The presence of a peculiarly bright, unresolved, and relatively broad He ii λ1640 emission in the central region at exactly the same PDLA redshift hints at the possibility that the PDLA originates in a clumpy outflow with a bulk velocity of about 500 km s−1. The smaller velocity dispersion of the large-scale Lyα emission suggests that the high-speed outflow is confined to the central region. Lastly, the derived spatially resolved He ii/Lyα and C iv/Lyα maps show a positive gradient with the distance to the QSO, hinting at a non-homogeneous distribution of the ionization parameter.

THE STACKED LYα EMISSION PROFILE FROM THE CIRCUM-GALACTIC MEDIUM OF z ∼ 2 QUASARS*

ABSTRACT In the context of the FLASHLIGHT survey, we obtained deep narrowband images of 15 z ∼ 2 quasars with the Gemini Multi-object Spectrograph on Gemini South in an effort to measure Lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Lyα nebulae (SB ∼ 10−17 erg s−1 cm−2 arcsec−2 at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale <50 kpc Lyα emission at this surface brightness level emerging from either the extended narrow emission line regions powered by the quasars or by star formation in their host galaxies. We stack our 15 deep images to study the average extended Lyα surface brightness profile around z ∼ 2 quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SBLyα ∼ 10−19 erg s−1 cm−2 arcsec−2 at ∼200 kpc, with a 2.3σ detection of Lyα emission at SB erg s−1 cm−2 arcsec−2 within an annulus spanning 50 kpc < R < 500 kpc from the quasars. Assuming that this Lyα emission is powered by fluorescence from highly ionized gas illuminated by the bright central quasar, we deduce an average volume density of n H = 0.6 × 10−2 cm−3 on these large scales. Our results are in broad agreement with the densities suggested by cosmological hydrodynamical simulations of massive (M ≃ 1012.5 M ⊙) quasar hosts; however, they indicate that the typical quasars at these redshifts are surrounded by gas that is a factor of ∼100 times less dense than the (∼1 cm−3) gas responsible for the giant bright Lyα nebulae around quasars recently discovered by our group.

Lyα blobs like company: the discovery of a candidate 100 kpc Lyα blob near to a radio galaxy with a giant Lyα halo B3 J2330+3927 at z = 3.1

Abstract We present the discovery of a candidate of giant radio-quiet Lyα blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Lyα halo B3 J2330+3927 at redshift z= 3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Lyα emitters (LAEs) and absorbers (LAAs) at redshift z= 3.09 ± 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 × 24 arcmin2 (58 × 44 comoving Mpc). We found that B3 J2330+3927 is surrounded by a 130 kpc Lyα halo and a large-scale (∼60 × 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8 arcmin (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Lyα nebulae in the same large-scale structure suggests that giant Lyα nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Lyα nebulae. First, RQLAB may need a prominent (δ∼ 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Lyα halo around HzRG may not always need a prominent density peak to form if the surrounding Lyα halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Lyα halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey.

VIMOS-VLT spectroscopy of the giant Ly nebulae associated with three z 2.5 radio galaxies

The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with three radio galaxies at z∼ 2.5 (MRC 1558–003, 2025–218 and 0140–257) have been investigated using integral field spectroscopic data obtained with the Visible Multi-Object Spectrograph (VIMOS) on VLT. The morphologies are varied. The nebula of one source has a centrally peaked, rounded appearance. In the other two objects, it consists of two spatial components. The three nebulae are aligned with the radio axis within ≲30°. The total Lyα luminosities are in the range (0.3–3.4) × 1044 erg s−1. The Lyα spectral profile shows strong variation through the nebulae, with full width at half-maximum (FWHM) values in the range ∼400–1500 km s−1 and velocity shifts Voffset∼ 120–600 km s−1. We present an infall model that can successfully explain the morphology, size, surface brightness distribution and the velocity field of the Lyα nebula associated with MRC 1558–003. It can also explain why Lyα is redshifted relative to other emission lines and the FWHM values of the non-resonant He ii line. This adds further support to our previous conclusion that the quiescent giant nebulae associated with this and other high-redshift powerful radio galaxies are in infall. A problem for this model is the difficulty to reproduce the large Lyα FWHM values, which might be the consequence of a different mechanism. We have discovered a giant (∼85 kpc) Lyα nebula associated with the radio galaxy MRC 0140–257 at z= 2.64. It shows strikingly relaxed kinematics (FWHM < 300 km s−1 and Voffset≲ 120 km s−1), unique among high-z (≳2) radio galaxies.

The giant Lyα nebula associated with a z = 2.5 radio galaxy

AbstractWe present a kinematic and morphological study of the giant Lyα nebula associated with the radio galaxy MRC 2104–242 (z = 2.49) based on integral field spectroscopic VIMOS data from VLT. The galaxy appears to be embedded in a giant (≃120 kpc) gas reservoir that surrounds it completely. The kinematic properties of the nebula suggest that it is a rotating structure, which would imply a lower limit to the dynamical mass of ∼3 × 1011 M⊙. An alternate scenario is that the gas is infalling. Such a process would be able to initiate and sustain significant central starburst activity, although it is likely to contribute with less than 10% of the total stellar mass of the galaxy. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

&amp;gt;VIMOS-VLT and Spitzer observations of a radio galaxy at z = 2.5

Abstract We present: (i) a kinematic and morphological study of the giant Lyα nebula associated with the radio galaxy MRC 2104−242 (z= 2.49) based on integral field spectroscopic Visible Multiobject Spectrograph (VIMOS) data from the Very Large Telescope (VLT), and (ii) a photometric study of the host (proto?) galaxy based on Spitzer Space Telescope data. The galaxy appears to be embedded in a giant (≳120 kpc) gas reservoir that surrounds it completely. The kinematic properties of the nebula suggest that it is a rotating structure, which would imply a lower limit to the dynamical mass of ∼3 × 1011 M⊙. An alternate scenario is that the gas is infalling. Such a process would be able to initiate and sustain significant central starburst activity, although it is likely to contribute with less than 10 per cent of the total stellar mass. The near- to mid-infrared spectral energy distribution of the radio galaxy suggests the existence of a reddened, E(B−V) = 0.4 ± 0.1, evolved stellar population of age ≳1.8 Gyr and mass (5 ± 2) × 1011 M⊙. The implied formation redshift is zf≳ 6. This stellar mass is similar to the stellar masses found for massive early-type galaxies at z∼ 2 in deep, near-infrared surveys.

Subaru Spectroscopy of the Giant Lyα Nebula around 1243+036

We present our new spatially-resolved, optical spectroscopy of the giant Lyα nebula around the powerful radio galaxy 1243+036 (=4C+03.24) at z = 3.57. The nebula is extended over ~ 30 kpc from the nucleus, and forms a pair of cones or elongated bubbles. The high-velocity (~ −1000 km s−1; blueshifted with respect to the systemic velocity) Lyα-emitting components are detected at both sides of the nucleus along its major axis. We discuss possible origin of the nebula; 1) the shock-heated expanding bubble or outflowing cone associated with the superwind activity of the host galaxy, 2) halo gas photoionized by the anisotropic radiation from the active galactic nuclei (AGN) and 3) the jet-induced star-formation or shock. The last possibility may not be likely because Lyα emission is distributed out of the narrow channel of the radio jet. We show that the superwind model is most plausible since it can explain both the characteristics of the morphology (size and shape) and the kinematical structures (velocity shift and line width) of the nebula although the photoionization by AGN may contribute to the excitation to some extent.

Giant Lyα Nebulae Associated with High‐Redshift Radio Galaxies

We report deep, Keck narrowband Lyα images of the luminous z > 3 radio galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc scale, emission-line nebulae, centered on these galaxies, that exhibit a wealth of morphological structure, including extended low surface brightness emission in the outer regions, radially directed filaments, cone-shaped structures and (indirect) evidence for extended Lyα absorption. We discuss these features within a general scenario in which the nebular gas cools gravitationally in large cold dark matter halos, forming stars and multiple stellar systems. Merging of these building blocks triggers large-scale starbursts, forming the stellar bulges of massive radio galaxy hosts, and feeds supermassive black holes, which produce the powerful radio jets and lobes. The radio sources, starburst superwinds, and radiation pressure from active galactic nucleus then disrupt the accretion process, limiting galaxy and black hole growth, and imprint the observed filamentary and cone-shaped structures of the Lyα nebulae.