We describe the Sloan

The fourth generation of the Sloan

We report the first results from the Clusters Around Radio-Loud AGN (CARLA) program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud AGN at 1.2 < z < 3.2. These data, obtained for 387 fields, reach 3.6 and 4.5 µm depths of [3.6] AB = 22.6 and [4.5] AB = 22.9 at the 95% completeness level, which is two to three times fainter than L * in this redshift range. By using the color cut [3.6]-[4.5] > −0.1 (AB), which efficiently selects high-redshift (z > 1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these IRAC-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a 2 σ level; 10% are overdense at a 5 σ level. A clear rise in surface density of IRAC-selected sources towards the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radioloud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars vs. obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.

The WISE mission has unveiled a rare population of high-redshift (z = 1 − 4.6), dusty, hyperluminous galaxies, with infrared luminosities L IR > 10 13 L ⊙ , and sometimes exceeding 10 14 L ⊙ . Previous work has shown that their dust temperatures and overall far-IR spectral energy distributions (SEDs) are significantly hotter than expected to be powered by star-formation. We present here an analysis of the rest-frame optical through mid-IR SEDs for a large sample of these so-called "Hot, Dust-Obscured Galaxies" (Hot DOGs). We find that the SEDs of Hot DOGs are generally well modeled by the combination of a luminous, yet obscured AGN that dominates the rest-frame emission at λ > 1µm and the bolometric luminosity output, and a less luminous host galaxy that is responsible for the bulk of the rest optical/UV emission. Even though the stellar mass of the host galaxies may be as large as 10 11 − 10 12 M ⊙ , the AGN emission, with a range of luminosities comparable to those of the most luminous QSOs known, require that either Hot DOGs have black hole masses significantly in excess of the local relations, or that they radiate significantly above the Eddington limit, at a level at least 10 times more efficiently than z ∼ 2 QSOs. We show that, while rare, the number density of Hot DOGs is comparable to that of equally luminous but unobscured (i.e., Type 1) QSOs. This may be at odds with the trend suggested at lower luminosities for the fraction of obscured AGN to decrease with increasing luminosity. That trend may, instead, reverse at higher luminosities. Alternatively, Hot DOGs may not be the torus-obscured counterparts of the known optically selected, largely unobscured Hyper-Luminous QSOs, and may represent a new component of the galaxy evolution paradigm. Finally, we discuss the environments of Hot DOGs and statistically show that these objects are in regions as dense as those of known high-redshift proto-clusters.

Black hole feedback is now a standard component of galaxy formation models. These models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2−3, the epoch of strongest star formation activity and black hole accretion activity in the Universe. We used XShooter on the Very Large Telescope to measure rest-frame optical spectra of four z ∼ 2.5 extremely red quasars with infrared luminosities ∼ 10 47 erg s −1 . We present the discovery of very broad (full width at half max= 2600 − 5000 km s −1 ), strongly blue-shifted (by up to 1500 km s −1 ) [OIII]λ5007Å emission lines in these objects. In a large sample of type 2 and red quasars, [OIII] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end both in [OIII] kinematics and infrared luminosity. We estimate that at least 3% of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. Photo-ionization estimates suggest that the [OIII] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. These sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active "blow-out" phase of quasar evolution.

The fourth generation of the Sloan

We present APEX LABOCA 870 μm observations of the field around the high-redshift radio galaxy MRC1138−262 at z = 2.16. We detect 16 submillimeter galaxies (SMGs) in this ∼140 arcmin 2 bolometer map with flux densities in the range 3-11 mJy. The raw number counts indicate a density of SMGs that is up to four times that of blank field surveys. Based on an exquisite multiwavelength database, including VLA 1.4 GHz radio and infrared observations, we investigate whether these sources are members of the protocluster structure at z ≈ 2.2. Using Herschel PACS and SPIRE and Spitzer MIPS photometry, we derive reliable far-infrared (FIR) photometric redshifts for all sources. Follow-up VLT ISAAC and SINFONI NIR spectra confirm that four of these SMGs have redshifts of z ≈ 2.2. We also present evidence that another SMG in this field, detected earlier at 850 μm, has a counterpart that exhibits Hα and CO(1-0) emission at z = 2.15. Including the radio galaxy and two SMGs with FIR photometric redshifts at z = 2.2, we conclude that at least eight submm sources are part of the protocluster at z = 2.16 associated with the radio galaxy MRC1138−262. We measure a star formation rate density SFRD ∼1500 M yr −1 Mpc −3 , four magnitudes higher than the global SFRD of blank fields at this redshift. Strikingly, these eight sources are concentrated within a region of 2 Mpc (the typical size of clusters in the local universe) and are distributed within the filaments traced by the HAEs at z ≈ 2.2. This concentration of massive, dusty starbursts is not centered on the submillimeter-bright radio galaxy which could support the infalling of these sources into the cluster center. Approximately half (6/11) of the SMGs that are covered by the Hα imaging data are associated with HAEs, demonstrating the potential of tracing SMG counterparts with this population. To summarize, our results demonstrate that submillimeter observations may enable us to study (proto)clusters of massive, dusty starbursts.

We present results from a comprehensive survey of 70 radio galaxies at redshifts 1 < z < 5.2 using the PACS and SPIRE instruments on board the Herschel Space Observatory. Combined with existing mid-IR photometry from the Spitzer Space Telescope, published 870 µm photometry, and new observations obtained with LABOCA on the APEX telescope, the spectral energy distributions (SEDs) of galaxies in our sample are continuously covered across 3.6-870 µm. The total 8-1000 µm restframe infrared luminosities of these radio galaxies are such that almost all of them are either ultra-(L IR tot > 10 12 L ) or hyper-luminous (L IR tot > 10 13 L ) infrared galaxies. We fit the infrared SEDs with a set of empirical templates which represent dust heated by a variety of starbursts (SB) and by an active galactic nucleus (AGN). We find that the SEDs of radio galaxies require the dust to be heated by both AGN and SB, but the luminosities of these two components are not strongly correlated. Assuming empirical relations and simple physical assumptions, we calculate the star formation rate (SFR), the black hole mass accretion rate (Ṁ BH ), and the black hole mass (M BH ) for each radio galaxy. We find that the host galaxies and their black holes are growing extremely rapidly, having SFR ≈ 100-5000 M yr −1 anḋ M BH ≈ 1-100 M yr −1 . The mean specific SFRs (sSFR) of radio galaxies at z > 2.5 are higher than the sSFR of typical star forming galaxies over the same redshift range, but are similar or perhaps lower than the galaxy population for radio galaxies at z < 2.5. By comparing the sSFR and the specificṀ BH (sṀ BH ), we conclude that black holes in radio loud AGN are already, or soon will be, overly massive compared to their host galaxies in terms of expectations from the local M BH -M Gal relation. In order to catch up with the black hole, the galaxies require about an order of magnitude more time to grow in mass at the observed SFRs compared to the time the black hole is actively accreting. However, during the current cycle of activity, we argue that this catching up is likely to be difficult because of the short gas depletion times. Finally, we speculate on how the host galaxies might grow sufficiently in stellar mass to ultimately fall onto the local M BH -M Gal relation.