ALMA detects molecular gas in the halo of the powerful radio galaxy TXS 0828+193

Both theoretical and observational results suggest that high-redshift radio galaxies (HzRGs) inhabit overdense regions of the universe and might be the progenitors of local, massive galaxies residing in the centre of galaxy clusters. In this paper we present CO(3-2) line observations of the HzRG TXS 0828+193 (z=2.57) and its environment using the Atacama Large Millimeter/submillimeter Array. In contrast to previous observations, we detect CO emission associated with the HzRG and derive a molecular gas mass of $(0.9\pm0.3)\times10^{10}\,\rm M_{\odot}$. Moreover, we confirm the presence of a previously detected off-source CO emitting region (companion #1), and detect three new potential companions. The molecular gas mass of each companion is comparable to that of the HzRG. Companion #1 is aligned with the axis of the radio jet and has stellar emission detected by Spitzer. Thus this source might be a normal star-forming galaxy or alternatively a result of jet-induced star formation. The newly found CO sources do not have counterparts in any other observing band and could be high-density clouds in the halo of TXS 0828+193 and thus potentially linked to the large-scale filamentary structure of the cosmic web.Comment: Accepted by MNRAS; 9 pages, 4 figure

Relation noyau actif et histoire de la formation d'étoiles dans les radio galaxies distantes

Les radio galaxies sont les candidats préférentiels pour comprendre la formation et l'évolution des galaxies sur une grande échelle de temps. Observées jusqu'à z>5 en raison de leur brillance, elles sont abritées par des galaxies elliptiques géantes. L'émission radio révèle la présence d'un trou noir supermassif. Un tore de poussière entourant le noyau actif de galaxie (AGN) agit comme un coronographe naturel permettant alors l'étude de la galaxie hôte. L'objectif de cette thèse est de déterminer l'évolution de la composante stellaire en présence d'un AGN. La décomposition est faite à partir de la distribution spectrale d'énergie (SED) de l'UV au submillimétrique en utilisant le code d'évolution de galaxies PEGASE.3 et un code d' AGN, les deux modélisant l'émission de la poussière par transfert radiatif.En premier lieu, nous présentons le projet HeRGE, 70 radio galaxies observées avec Herschel, qui permet de mesurer leurs luminosités totales infrarouges, comparables à celles des ULIRG. Une décomposition de la luminosité infrarouge entre l'émission AGN et un modèle de starburst est proposée pour l'ensemble de l'échantillon. Ces luminosités élevées sont interprétées en termes de taux d'accrétion et de formation d'étoiles, favorisant la croissance du trou noir par rapport à la galaxie hôte.En second lieu, l'orientation du jet par rapport au tore est contrainte à partir de l'infrarouge moyen et du rapport des émissions radio des lobes (isotrope, 500MHz) et du coeur (anisotrope, 20GHz). Ces observations en accord avec le modèle d'unification permettent d'évaluer le facteur d'absorption Av, l'inclinaison du tore et de contraindre le facteur de Lorentz.Une sélection de 12 radio galaxies observées de l'UV au sub-mm est analysée avec PEGASE.3 et un modèle d'AGN. Une seule composante stellaire est insuffisante. Seules deux composantes (une évoluée et massive, et une jeune issue d'un starburst) permettent un ajustement significatif de la SED complète. La composante évoluée est très massive (environ 10^12 msun) formée sur une courte période de temps (5 and are commonly associated with the massive early-type galaxies observed in the local universe. While the radio emission reveals the presence of a supermassive black hole, a dusty parsec-scale torus acts like a natural coronograph, making it easier to study the properties of the host galaxy. The aim of this PhD thesis is to characterise the nature and evolution of the stellar population and the relationship between the stellar population and the active galactic nucleus (AGN). To reach our scientific goals, we use the galaxy evolution code, PEGASE, combined with a AGN model which both consider the radiative transfer of the UV, optical, and IR photons through dust. To begin, we present the HeRGE project consisting of 70 radio galaxies which have been observed with Herschel. These IR observations allow us to calculate the total infrared luminosities and reveal that our sample belongs to the ULIRG regime. We decompose the infrared SED into an AGN and starburst components using observational templates. Converted into accretion and star formation rate, their relative luminosities indicate that the black holes are growing proportionally faster than are the host galaxies.In addition, we constrain the configuration of the jet and torus by combining the results from mid-infrared spectral energy distribution (SED), and the radio emission from the lobes (isotropic at 500MHz) and the core (anisotropic at 20GHz). In agreement with the unified scheme, these observations allow us to estimate the absorption Av, the inclination of the torus, and provides a constraint on the Lorentz factor for the radio jet.A subsample of 12 radio galaxies observed from the UV to sub-mm is also analysed with PEGASE.3 and an AGN torus model. While one stellar component is clearly insufficient to fit the observations, two stellar components are necessary to successfully reproduce the SED (one evolved and massive, about 10^12 msun, formed over a reasonably short time, <1Gyr at high redshift; and a much younger component, <40Myr, that is also less massive, about 10^11 msun. Such a star formation history suggests rapid growth at high redshift of longer duration followed much by another period of rapid, stochastic growth.These results put strong constraints on galaxy formation models. Unfortunately, the crudeness of some of our data and theoretical understanding the IR emission from AGN, means that the relation of the galaxy to its AGN is still not well constrained. Additional observations at optical through millimeter wavelengths are needed to extend our findings.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

SMM J04135+10277: a distant QSO-starburst system caught by ALMA

The gas content of galaxies is a key factor for their growth, starting from star formation and black hole accretion to galaxy mergers. Thus, characterizing its properties through observations of tracers like the CO emission line is of big importance in order to understand the bigger picture of galaxy evolution. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, CO(5-4) and CO(8-7) line emission in the quasar-star-forming companion system SMM J04135+10277 (z = 2.84). Earlier low-J CO studies of this system found a huge molecular gas reservoir associated with the companion galaxy, while the quasar appeared gas-poor. Our CO observations revealed that the host galaxy of the quasar is also gas-rich, with an estimated molecular gas mass of ∼ (0.7-2.3) 7 10^{10} M_{☉}. The CO line profiles of the companion galaxy are very broad (∼ 1000 km s^{-1}), and show signs of rotation of a compact, massive system. In contrast to previous far-infrared observations, we resolve the continuum emission and detect both sources, with the companion galaxy dominating the dust continuum and the quasar having a ∼ 25{{ per cent}} contribution to the total dust emission. By fitting the infrared spectral energy distribution of the sources with MR-MOOSE and empirical templates, the infrared luminosities of the quasar and the companion are in the range of L_{IR, QSO}∼ (2.1-9.6) 7 10^{12} L_{☉} and L_{IR, Comp.}∼ (2.4-24) 7 10^{12} L_{☉}, while the estimated star formation rates are ∼ 210-960 and ∼ 240-2400 M_{☉} yr^{-1}, respectively. Our results demonstrate that non-detection of low-J CO transition lines in similar sources does not necessarily imply the absence of massive molecular gas reservoir but that the excitation conditions favour the excitation of high-J transitions

The Dragonfly Galaxy. III. Jet-brightening of a High-redshift Radio Source Caught in a Violent Merger of Disk Galaxies

The Dragonfly Galaxy (MRC 0152-209), the most infrared-luminous radio galaxy at redshift z~2, is a merger system containing a powerful radio source and large displacements of gas. We present kpc-resolution data from ALMA and the VLA of carbon monoxide (6-5), dust, and synchrotron continuum, combined with Keck integral-field spectroscopy. We find that the Dragonfly consists of two galaxies with rotating disks that are in the early phase of merging. The radio jet originates from the northern galaxy and brightens when it hits the disk of the southern galaxy. The Dragonfly Galaxy therefore likely appears as a powerful radio galaxy because its flux is boosted into the regime of high-z radio galaxies by the jet-disk interaction. We also find a molecular outflow of (1100 $\pm$ 550) M$_{\odot}$/yr associated with the radio host galaxy, but not with the radio hot-spot or southern galaxy, which is the galaxy that hosts the bulk of the star formation. Gravitational effects of the merger drive a slower and longer lived mass displacement at a rate of (170 $\pm$ 40) M$_{\odot}$/yr, but this tidal debris contain at least as much molecular gas mass as the much faster outflow, namely M(H2) = (3 $\pm$ 1) x 10$^9$ (alpha(CO)/0.8) M$_{\odot}$. This suggests that both the AGN-driven outflow and mass transfer due to tidal effects are important in the evolution of the Dragonfly system. The Keck data show Ly$\alpha$ emission spread across 100 kpc, and CIV and HeII emission across 35 kpc, confirming the presence of a metal-rich and extended circumgalactic medium previously detected in CO(1-0).Comment: Accepted for publication in ApJ (15 pages, 9 figures

ALMA finds dew drops in the dusty spider’s web

We present 0.̋5 resolution ALMA detections of the observed 246 GHz continuum, [CI] 3P2→3P1 fine structure line ([CI]2–1), CO(7–6), and H2O lines in the z = 2.161 radio galaxy MRC1138-262, the so-called Spiderweb galaxy. We detect strong [CI]2–1 emission both at the position of the radio core, and in a second component ~4 kpc away from it. The 1100 km s-1 broad [CI]2–1 line in this latter component, combined with its H2 mass of 1.6 × 1010 M⊙, implies that this emission must come from a compact region <60 pc, possibly containing a second active galactic nucleus (AGN). The combined H2 mass derived for both objects, using the [CI]2–1 emission, is 3.3 × 1010 M⊙. The total CO(7–6)/[CI]2–1 line flux ratio of 0.2 suggests a low excitation molecular gas reservoir and/or enhanced atomic carbon in cosmic ray dominated regions. We detect spatially-resolved H2O 211−202 emission – for the first time in a high-z unlensed galaxy – near the outer radio lobe to the east, and near the bend of the radio jet to the west of the radio galaxy. No underlying 246 GHz continuum emission is seen at either position. We suggest that the H2O emission is excited in the cooling region behind slow (10–40 km s-1) shocks in dense molecular gas (103−5 cm-3). The extended water emission is likely evidence of the radio jet’s impact on cooling and forming molecules in the post-shocked gas in the halo and inter-cluster gas, similar to what is seen in low-z clusters and other high-z radio galaxies. These observations imply that the passage of the radio jet in the interstellar and inter-cluster medium not only heats gas to high temperatures, as is commonly assumed or found in simulations, but also induces cooling and dissipation, which can lead to substantial amounts of cold dense molecular gas. The formation of molecules and strong dissipation in the halo gas of MRC1138-262 may explain both the extended diffuse molecular gas and the young stars observed around MRC1138-262

3D tomography of the giant Lyα nebulae of z ≈ 3–5 radio-loud AGN

Lyα emission nebulae are ubiquitous around high-redshift galaxies and are tracers of the gaseous environment on scales out to ≳100 pkpc (proper kiloparsec). High-redshift radio galaxies (HzRGs, type-2 radio-loud quasars) host large-scale nebulae observed in the ionised gas differ from those seen in other types of high-redshift quasars. In this work, we exploit MUSE observations of Lyα nebulae around eight HzRGs (2.92 < z < 4.51). All of the HzRGs have large-scale Lyα emission nebulae with seven of them extended over 100 pkpc at the observed surface brightness limit (∼2 − 20 × 10−19 erg s−1 cm−2 arcsec−2). Because the emission line profiles are significantly affected by neutral hydrogen absorbers across the entire nebulae extent, we performed an absorption correction to infer maps of the intrinsic Lyα surface brightness, central velocity, and velocity width, all at the last scattering surface of the observed Lyα photons. We find the following: (i) that the intrinsic surface brightness radial profiles of our sample can be described by an inner exponential profile and a power law in the low luminosity extended part; (ii) our HzRGs have a higher surface brightness and more asymmetric nebulae than both radio-loud and radio-quiet type-1 quasars; (iii) intrinsic nebula kinematics of four HzRGs show evidence of jet-driven outflows but we find no general trends for the whole sample; (iv) a relation between the maximum spatial extent of the Lyα nebula and the projected distance between the active galactic nuclei (AGN) and the centroids of the Lyα nebula; and (v) an alignment between radio jet position angles and the Lyα nebula morphology. All of these findings support a scenario in which the orientation of the AGN has an impact on the observed nebular morphologies and resonant scattering may affect the shape of the surface brightness profiles, nebular kinematics, and relations between the observed Lyα morphologies. Furthermore, we find evidence showing that the outskirts of the ionised gas nebulae may be ‘contaminated’ by Lyα photons from nearby emission halos and that the radio jet affects the morphology and kinematics of the nebulae. Overall, this work provides results that allow us to compare Lyα nebulae around various classes of quasars at and beyond cosmic noon (z ∼ 3)

The mysterious morphology of MRC0943-242 as revealed by ALMA and MUSE

© 2016 ESO. We present a pilot study of the z = 2.923 radio galaxy MRC0943-242, where we combine information from ALMA and MUSE data cubes for the first time. Even with modest integration times, we disentangle the AGN and starburst dominated components. These data reveal a highly complex morphology as the AGN, starburst, and molecular gas components show up as widely separated sources in dust continuum, optical continuum, and CO line emission observations. CO(1-0) and CO(8-7) line emission suggest that there is a molecular gas reservoir offset from both the dust and the optical continuum that is located ~90 kpc from the AGN. The UV line emission has a complex structure in emission and absorption. The line emission is mostly due to a large scale ionisation cone energised by the AGN, and a Lya emitting bridge of gas between the radio galaxy and a heavily star-forming set of components. Strangely, the ionisation cone has no Lya emission. We find this is due to an optically thick layer of neutral gas with unity covering fraction spread out over a region of at least ~100 kpc from the AGN. Other less thick absorption components are associated with Lya emitting gas within a few tens of kpc from the radio galaxy and are connected by a bridge of emission. We speculate that this linear structure of dust, Lya and CO emission, and the redshifted absorption seen in the circum nuclear region may represent an accretion flow feeding gas into this massive AGN host galaxy

AGN and star formation history in high redshift radio galaxies

Les radio galaxies sont les candidats préférentiels pour comprendre la formation et l'évolution des galaxies sur une grande échelle de temps. Observées jusqu'à z>5 en raison de leur brillance, elles sont abritées par des galaxies elliptiques géantes. L'émission radio révèle la présence d'un trou noir supermassif. Un tore de poussière entourant le noyau actif de galaxie (AGN) agit comme un coronographe naturel permettant alors l'étude de la galaxie hôte. L'objectif de cette thèse est de déterminer l'évolution de la composante stellaire en présence d'un AGN. La décomposition est faite à partir de la distribution spectrale d'énergie (SED) de l'UV au submillimétrique en utilisant le code d'évolution de galaxies PEGASE.3 et un code d' AGN, les deux modélisant l'émission de la poussière par transfert radiatif.En premier lieu, nous présentons le projet HeRGE, 70 radio galaxies observées avec Herschel, qui permet de mesurer leurs luminosités totales infrarouges, comparables à celles des ULIRG. Une décomposition de la luminosité infrarouge entre l'émission AGN et un modèle de starburst est proposée pour l'ensemble de l'échantillon. Ces luminosités élevées sont interprétées en termes de taux d'accrétion et de formation d'étoiles, favorisant la croissance du trou noir par rapport à la galaxie hôte.En second lieu, l'orientation du jet par rapport au tore est contrainte à partir de l'infrarouge moyen et du rapport des émissions radio des lobes (isotrope, 500MHz) et du coeur (anisotrope, 20GHz). Ces observations en accord avec le modèle d'unification permettent d'évaluer le facteur d'absorption Av, l'inclinaison du tore et de contraindre le facteur de Lorentz.Une sélection de 12 radio galaxies observées de l'UV au sub-mm est analysée avec PEGASE.3 et un modèle d'AGN. Une seule composante stellaire est insuffisante. Seules deux composantes (une évoluée et massive, et une jeune issue d'un starburst) permettent un ajustement significatif de la SED complète. La composante évoluée est très massive (environ 10^12 msun) formée sur une courte période de temps (5 and are commonly associated with the massive early-type galaxies observed in the local universe. While the radio emission reveals the presence of a supermassive black hole, a dusty parsec-scale torus acts like a natural coronograph, making it easier to study the properties of the host galaxy. The aim of this PhD thesis is to characterise the nature and evolution of the stellar population and the relationship between the stellar population and the active galactic nucleus (AGN). To reach our scientific goals, we use the galaxy evolution code, PEGASE, combined with a AGN model which both consider the radiative transfer of the UV, optical, and IR photons through dust. To begin, we present the HeRGE project consisting of 70 radio galaxies which have been observed with Herschel. These IR observations allow us to calculate the total infrared luminosities and reveal that our sample belongs to the ULIRG regime. We decompose the infrared SED into an AGN and starburst components using observational templates. Converted into accretion and star formation rate, their relative luminosities indicate that the black holes are growing proportionally faster than are the host galaxies.In addition, we constrain the configuration of the jet and torus by combining the results from mid-infrared spectral energy distribution (SED), and the radio emission from the lobes (isotropic at 500MHz) and the core (anisotropic at 20GHz). In agreement with the unified scheme, these observations allow us to estimate the absorption Av, the inclination of the torus, and provides a constraint on the Lorentz factor for the radio jet.A subsample of 12 radio galaxies observed from the UV to sub-mm is also analysed with PEGASE.3 and an AGN torus model. While one stellar component is clearly insufficient to fit the observations, two stellar components are necessary to successfully reproduce the SED (one evolved and massive, about 10^12 msun, formed over a reasonably short time, <1Gyr at high redshift; and a much younger component, <40Myr, that is also less massive, about 10^11 msun. Such a star formation history suggests rapid growth at high redshift of longer duration followed much by another period of rapid, stochastic growth.These results put strong constraints on galaxy formation models. Unfortunately, the crudeness of some of our data and theoretical understanding the IR emission from AGN, means that the relation of the galaxy to its AGN is still not well constrained. Additional observations at optical through millimeter wavelengths are needed to extend our findings