Implications of the Environments of Radio-detected AGN in a Complex Protostructure at z$\sim$3.3
Lu Shen, Brian C. Lemaux, Lori M. Lubin, Olga Cucciati, Olivier Le Fevre, Guilin Liu, Wenjuan Fang, Debora Pelliccia, Adam Tomczak, John McKean, Neal A. Miller,… 展开作者
Lu Shen, Brian C. Lemaux, Lori M. Lubin, Olga Cucciati, Olivier Le Fevre, Guilin Liu, Wenjuan Fang, Debora Pelliccia, Adam Tomczak, John McKean, Neal A. Miller, Christopher D. Fassnacht, Roy Gal, Denise Hung, Nimish Hathi, Sandro Bardelli, Daniela Vergani, Elena Zucca
Radio Active Galactic Nuclei (RAGNs) are mainly found in dense structures (i.e., clusters/groups) at redshifts of z$<$2 and are commonly used to detect protoclusters at higher redshift. Here, we attempt to study the host and environmental properties of two relatively faint ($\mathrm L_\mathrm{1.4GHz} \sim10^{25}$ W Hz$^{-1}$) RAGNs in a known protocluster at z=3.3 in the PCl J0227-0421 field, detected using the latest radio observation obtained as part of the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) Survey. Using new spectroscopic observations obtained from Keck/MOSFIRE as part of the Charting Cluster Construction with the VIMOS Ultra-Deep Survey (VUDS) and ORELSE (C3VO) survey and previous spectroscopic data obtained as part of the VIMOS-VLT Deep Survey (VVDS) and VUDS, we revise the three-dimensional overdensity field around this protocluster. The protocluster is embedded in a large scale overdensity protostructure. This protostructure has an estimated total mass of $\sim$2.6$\times10^{15} M_\odot$ and contains several overdensity peaks. Both RAGNs are hosted by very bright and massive galaxies, while their hosts show extreme differences color, indicating that they have different ages and are in different evolutionary stages. Furthermore, we find that they are not in the most locally dense parts of the protostructure, but are fairly close to the centers of their parent overdensity peaks. We propose a scenario where merging might already have happened in both cases, which lowered the local density of their surrounding area and boosted their stellar mass. This work is the first time that two RAGNs at low luminosity have been found and studied within a high redshift protostructure.
Enhanced AGN Activity in Overdense Galactic Environments at $2 < z < 4$
University of California, Davis（加州大学戴维斯分校）；Gemini Observatory（双子座天文台）；Space Telescope Science Institute（太空望远镜科学研究所）；Texas A&M University（德克萨斯农工大学）；INAF-Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所空间科学观测站）；University of Hawai'i, Institute for Astronomy（夏威夷大学天文学研究所）
研究发现，在2 < z < 4的红移区间内，高密度星系环境中的AGN活动比例显著高于孤立星系，且这一趋势在不同AGN类别和红移区间内均一致存在。
In this study we investigate 179 radio-IR galaxies drawn from a sample of spectroscopically-confirmed galaxies that are detected in radio and mid-infrared (MIR) in the redshift range of $0.55 \leq z \leq 1.30$ in the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. We constrain the Active Galactic Nuclei (AGN) contribution in the total IR luminosity (f$_{\text{AGN}}$), and estimate the AGN luminosity (L$_{\text{AGN}}$) and the star formation rate (SFR) using the CIGALE Spectral Energy Distribution (SED) fitting routine. Based on the f$_{\text{AGN}}$ and radio lum…
Radio emission in star-forming galaxies: connection to restarted or relic AGN activity
Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学中心，天文计算研究所）；Departamento de Física, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria（圣卡塔琳娜联邦大学自然科学与精确科学中心物理系）；Departamento de Astronomia, Instituto de Física, Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学物理系天文学系）
In this study, we analysed active galactic nuclei in the "green valley" by comparing active and non-active galaxies using data from the COSMOS field. We found that most of our X-ray detected active galactic nuclei with far-infrared emission have star formation rates higher than the ones of normal galaxies of the same stellar mass range.
We investigate the nature of far-infrared (70 um) and hard X-ray (3-24 keV) selected galaxies in the COSMOS field detected with both Spitzer and Nuclear Spectroscopic Telescope Array (NuSTAR). By matching the Spitzer-COSMOS catalog against the NuSTAR-COSMOS catalog, we obtain a sample consisting of a hyperluminous infrared galaxy with log(L_IR/L_sun) > 13, 12 ultraluminous infrared galaxies with 12 < log(L_IR/L_sun) < 13, and 10 luminous infrared galaxies with 11 < log(L_IR/L_sun) < 12, i.e., 23 Hy/U/LIRGs in total. Using their X-ray hardness ratios, we find that 12 sources are obscured active…
In this paper we present the star formation properties of $\rm{I_{subaru}\leq}$ 23 X-ray detected AGN and non-AGN galaxies in the green valley with far-IR (FIR) emission, using data from the COSMOS field. We measured star formation rates (SFR) using FIR Herschel/PACS data and we observed the location of AGN and non-AGN galaxies on the main-sequence of star formation. We went a step further in analysing the importance of AGN in quenching star formation in the green valley, the region proposed to be the transitional phase in galaxy evolution where galaxies are moving from later- to earlier-types…
Recent studies have found that radio-AGN selected by radio-loudness show little difference in terms of their host galaxy properties when compared to non-AGN galaxies of similar stellar mass and redshift. Using new 1.4~GHz VLBI observations of the COSMOS field we find that approximately 49$\pm8$\% of high-mass (M $>$ 10$^{10.5}$ M$_{\odot}$), high luminosity (L$_{1.4}$ $>$ 10$^{24}$ W~Hz$^{-1}$) radio-AGN possess a VLBI detected counterpart. These objects show no discernible bias towards specific stellar masses, redshifts or host properties other than what is shown by the radio-AGN population i…
Using observations from the first two years of the MOSFIRE Deep Evolution Field (MOSDEF) survey, we study 13 AGN-driven outflows detected from a sample of 67 X-ray, IR and/or optically-selected AGN at $z \sim 2$. The AGN have bolometric luminosities of $\sim10^{44}-10^{46} ~\mathrm{erg~s^{-1}}$, including both quasars and moderate-luminosity AGN. We detect blueshifted, ionized gas outflows in the H$β$ , [OIII], H$α$ ~and/or [NII] emission lines of $19\%$ of the AGN, while only 1.8\% of the MOSDEF galaxies have similarly-detected outflows. The outflow velocities span $\sim$300 to 1000 km s$^{-1…
We present JCMT SCUBA-2 850microns submillimetre (submm) observations of 30 mid-infrared (mid-IR) luminous AGN, detected jointly by the WISE all-sky IR survey and the NVSS/FIRST radio survey. These rare sources are selected by their extremely red mid-infrared spectral energy distributions (SEDs) and compact radio counterparts. Further investigations show that they are highly obscured, have abundant warm AGN-heated dust and are thought to be experiencing intense AGN feedback. These galaxies appear to be consistent with an AGN-dominated galaxy, and could be a transient phase of merging galaxies.…
In this work we present a robust quantification of X-ray selected AGN in local ($z \leq 0.25$) dwarf galaxies ($M_\mathrm{*} \leq 3 \times 10^9 \mathrm{M_\odot}$). We define a parent sample of 4,331 dwarf galaxies found within the footprint of both the MPA-JHU galaxy catalogue (based on SDSS DR8) and 3XMM DR7, performed a careful review of the data to remove misidentifications and produced a sample of 61 dwarf galaxies that exhibit nuclear X-ray activity indicative of an AGN. We examine the optical emission line ratios of our X-ray selected sample and find that optical AGN diagnostics fail to …
Spitzer/IRAC color selection is a promising technique to identify hot accreting nuclei, that is to say AGN, in galaxies. We demonstrate this using a small sample of SAURON galaxies, and explore this further. The goal of this study is to find a simple and efficient way to reveal optically obscured nuclear accretion in (nearby) galaxies. We apply an infrared selection method to the Spitzer Survey of Stellar Structures in Galaxies (S4G) sample of more than 2500 galaxies, together with its extension sample of more than 400 galaxies. We use the Spitzer colors to find galaxies in the S$^{4}$G survey…
NGC 7582 is an SB(s)ab galaxy which displays evidences of simultaneous nuclear activity and star formation in its centre. Previous optical observations revealed, besides the H II regions, an ionization cone and a gas disc in its central part. Hubble Space Telescope (HST) images in both optical and infrared bands show the active galactic nuclei (AGNs) and a few compact structures that are possibly associated with young stellar clusters. In order to study in detail both the AGN and evidence for star formation, we analyse optical (Gemini Multi-Object Spectrograph) and near-infrared (Spectrograph …
The sub-arcsecond ILT view of the Boötes Deep Field: A link between low-frequency kiloparsec radio morphology and AGN driven ionised outflows
Durham University（杜伦大学）；CSIRO（澳大利亚联邦科学与工业研究组织）；Newcastle University（纽卡斯尔大学）；Leiden University（莱顿大学）；ASTRON, The Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；University of Bristol（布里斯托大学）；INAF-IRA（意大利国家天体物理研究所罗马分所）
We identify 85 variable galaxies in the GOODS North and South fields using 5 epochs of HST ACS V-band (F606W) images spanning 6 months. The variables are identified through significant flux changes in the galaxy's nucleus and represent ~2% of the survey galaxies. With the aim of studying the active galaxy population in the GOODS fields, we compare the variability-selected sample with X-ray and mid-IR AGN candidates. Forty-nine percent of the variables are associated with X-ray sources identified in the 2Ms Chandra surveys. Twenty-four percent of X-ray sources likely to be AGN are optical varia…
The discovery over the last several decades of moderate luminosity AGNs in disk-dominated galaxies - which show no "classical" bulges - suggests that secular mechanisms represent an important growth pathway for supermassive black holes in these systems. We present new follow-up NuSTAR observations of the optically-elusive AGNs in two bulgeless galaxies, NGC 4178 and J0851+3926. NGC 4178 was originally reported as hosting an AGN based on the detection of [Ne V] mid-infrared emission detected by Spitzer, and based on Chandra X-ray imaging it has since been argued to host either a heavily obscure…
We present the results from a systematic search for galactic-scale, molecular (OH 119 $μ$m) outflows in a sample of 52 Local Volume ($d < 50$ Mpc) Burst Alert Telescope detected active galactic nuclei (BAT AGN) with \emph{Herschel}-PACS. We combine the results from our analysis of the BAT AGN with the published \emph{Herschel}/PACS data of 43 nearby ($z<0.3$) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. The objects in our sample of BAT AGN have, on average, $\sim 10-100$ times lower AGN luminosities, star formation rates (SFRs), and stellar masses than those of the…
Dynamical mechanisms are essential to exchange angular momentum in galaxies, drive the gas to the center, and fuel the central super-massive black holes. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching 10pc scale have revealed, within the sphere of influence of the black hole, smoking gun evidence of fueling. Observations of AGN feedback are described, together with the suspected responsible mechanisms. Molecular outflows are frequently detected in active galaxies with ALMA and NOEMA, with loading factors between 1 and 5. When driven by AGN wit…
We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{μJy}$ ($1σ$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that…
We present the X-ray properties of 108 Dust-Obscured Galaxies (DOGs; F$_{24 μm}$/F$_{R} >$ 1000) in the COSMOS field, all of which detected in at least three far-infrared bands with the Herschel Observatory. Out of the entire sample, 22 are individually detected in the hard 2-8 keV X-ray band by the Chandra COSMOS Legacy survey, allowing us to classify them as AGN. Of them, 6 (27%) are Compton Thick AGN candidates with column densities N$_{H}$$>$10$^{24}$ cm$^{-2}$ while 15 are moderately obscured AGNs with 10$^{22}$ $<$ N$_{H}$ $<$ 10$^{24}$ cm$^{-2}$. Additionally, we estimate AGN contributi…
We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of $μ$Jy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, i.e., it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compa…
We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at $z<1$. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses $M_{\star}<3\times 10^{9} M_{\odot}$ that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of $\sim 5\times 10^{-17} - 6\times 10^{-16} \rm{erg \ cm}^{-2} \ \rm{s}^{-1}$) archival Chandra X-ray data. From our sample of $605$ dwarf galaxies, $10$ exhibit X-ray emission consistent with that arising from AGN activity. If black hole mass scales roughly with stellar mass,…
We study Active Galactic Nucleus (AGN) activity in the fossil galaxy cluster, RX J1416.4+2315. Radio observations were carried out using Giant Metrewave Radio Telescope (GMRT) at two frequencies, 1420 MHz and 610 MHz. A weak radio lobe that extends from the central nucleus is detected in 610 MHz map. Assuming the radio lobe originated from the central AGN, we show the energy injection into the Inter Galactic Medium (IGM) is only sufficient to heat up the central 50 kpc within the cluster core, while the cooling radius is larger ( $\sim$ 130 kpc). In the hardness ratio map, three low energy cav…
We report herschel observations of 100 very luminous, optically selected AGNs at z=2-3.5 with log(LUV)(erg/sec)> 46.5, where LUV=L1350A. The distribution in LUV is similar to the general distribution of SDSS AGNs in this redshift and luminosity interval. We measured SF luminosity, LSF, and SFR in 34 detected sources by fitting combined SF and WISE-based torus templates. We also obtained statistically significant stacks for the undetected sources in two luminosity groups. The sample properties are compared with those of very luminous AGNs at z>4.5. The main findings are: 1) The mean and the med…
The aim of this work is to characterize physical properties of Ultra Luminous Infrared Galaxies (ULIRGs) and Luminous Infrared Galaxies (LIRGs) detected in the far-infrared (FIR) 90um band in the AKARI Deep Field-South (ADF-S) survey. In particular, we want to estimate the AGN contribution to the [U]LIRGs' infrared emission and which types of AGNs are related to their activity. We examined 69 galaxies at z>0.05 detected at 90um by the AKARI satellite in the ADF-S, with optical counterparts and spectral coverage from the ultraviolet to the FIR. We used two independent spectral energy distributi…
The properties of low-mass galaxies hosting central black holes provide clues about the formation and evolution of the progenitors of supermassive black holes. In this letter, we present HSC-XD 52, a spectroscopically confirmed low-mass active galactic nucleus (AGN) at an intermediate redshift of $z\sim0.56$. We detect this object as a very luminous X-ray source coincident with a galaxy observed by the Hyper Suprime-Cam (HSC) as part of a broader search for low-mass AGN. We constrain its stellar mass through spectral energy distribution modeling to be LMC-like at $M_\star \approx 3 \times 10^9…
Double-peaked emission line AGN (DPAGN) have been regarded as binary black hole candidates. We present here results from parsec-scale radio observations with the Very Long Baseline Array (VLBA) of five DPAGN belonging to the KISSR sample of emission-line galaxies. This work concludes our pilot study of nine type 2 Seyfert and LINER DPAGN from the KISSR sample. In the nine sources, dual compact cores are only detected in the "offset AGN", KISSR 102. The overall incidence of jets however, in the eight sources detected with the VLBA, is $\ge$60%. We find a difference in the "missing flux density"…
A relationship between the water maser detection rate and large nuclear column densities in AGN has often been cited in the literature. Indeed, detailed studies of luminous water masers, typically associated with the nuclear activity, allow us to investigate the innermost regions of AGN, with an impact on the still debated Unified Model for this class of objects.We have recently entertained a search for maser emission in a well-defined sample of Compton-thick AGN aimed at investigating, on firm statistical bases, the aforementioned relationship. While the survey is still ongoing, and is matter…
Aims. We present a sample of 4388 AGNs with available radio core-dominance parameters defined as the ratio of the core flux densities to extended ones, namely, R = Score/Sext., which includes 630 Fermi-detected AGNs respect to the catalog of 4FGL, the fourth Fermi Large Area Telescope source catalog, and the rest of them are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not, and also consists of other subclasses such as Seyfert, Fanaroff-Riley I/II and normal galaxies. We investigate various different properties between Fermi-detected AGNs and non-Fermi-de…
SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV survey running in parallel to the eBOSS cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected AGN and galaxy cluster members detected in wide area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS: X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colour-magnitude inform…
We report the results of an investigation to determine the nature of the offset active galactic nucleus (AGN) found in the source CXO J101527.2+625911. Hubble Space Telescope and Chandra X-ray observatory data had suggested that the offset AGN, which has an angular separation of only 0\farcs26 from the center of the host galaxy, is a recoiled Super Massive Black Hole (rSMBH). We carried out high angular resolution observations with both the VLBA (1.54 GHz) and the VLA (10.0 GHz \& 33.0 GHz) and detected a single compact radio source in the center of the host galaxy, with no radio continuum emi…
We study the fraction of dual AGN in a sample of 167 nearby (z<0.05), moderate luminosity, ultra hard X-ray selected AGN from the all-sky Swift BAT survey. Combining new Chandra and Gemini observations together with optical and X-ray observations, we find that the dual AGN frequency at scales <100 kpc is 10% (16/167). Of the 16 dual AGN, 3 (19%) were detected using X-ray spectroscopy and were not detected using emission line diagnostics. Close dual AGN (<30 kpc) tend to be more common among the most X-ray luminous systems. In dual AGN, the X-ray luminosity of both AGN increases strongly with d…
Supermassive black hole (SMBH) binaries form due to galaxy mergers and minor accretion events. When the SMBHs are accreting, they form dual or binary AGN and can give rise to double-peaked emission lines in the optical spectra of the merger remnant. The double-peaked emission lines could also be due to jet-ISM interaction or rotating disks. One of the best ways to confirm dual/binary AGN in double-peaked AGN (DPAGN) is by using high resolution radio observations. We have observed a sample of 20 DPAGN at two or more frequencies using the Karl G. Jansky Very Large Array (VLA), of which one sourc…
We present the radio properties of 66 spectroscopically-confirmed normal star-forming galaxies (SFGs) at $4.4<z<5.9$ in the COSMOS field that were [C II] detected in the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C II] at Early times (ALPINE). We separate these galaxies ("CII-detected-all") into lower redshift ("CII-detected-lz", $\langle z\rangle=4.5$) and higher redshift ("CII-detected-hz", $\langle z\rangle=5.6$) sub-samples and stack multi-wavelength imaging for each sub-sample from X-ray to radio bands. A radio signal is detected in the stacked 3 GHz image of CII-…
VLT/MUSE Study of Close AGN Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized Gas
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University（南京大学现代天文与天体物理实验室）；Institute of Science and Technology for Deep Space Exploration, Suzhou Campus, Nanjing University（南京大学苏州校区深空探测研究院）；Department of Astronomy, Xiamen University（厦门大学天文学系）；European Southern Observatory（欧洲南方天文台）
Jets from active galactic nuclei (AGN) are known to recurrently enrich their surrounding medium with mildly-relativistic particles and magnetic fields. Here, we present a detailed multi-frequency analysis of the nearby (z=0.01646) galaxy group NGC 507. In particular, we present new high-sensitivity and high spatial resolution radio images in the frequency range 144-675 MHz obtained using LOFAR and uGMRT observations. These reveal the presence of previously undetected diffuse radio emission with complex, filamentary morphology, likely related to a previous outburst of the central galaxy. Based …
We aim to study the effect of environment on the presence and fuelling of Active Galactic Nuclei (AGN) in massive galaxy clusters. We explore the use of different AGN detection techniques with the goal of selecting AGN across a broad range of luminosities, AGN/host galaxy flux ratios, and obscuration levels. From a sample of 12 galaxy clusters at redshifts 0.5 < z < 0.9, we identify AGN candidates using optical variability from multi-epoch HST imaging, X-ray point sources in Chandra images, and mid-IR SED power-law fits through the Spitzer IRAC channels. We find 178 optical variables, 74 X-ray…
Radio-detected Lya emitters at 1.88 < z < 3.52: AGN fraction and Lya emission
Leiden University（莱顿大学）；NSF NOIRLab, Gemini Observatory（美国国家科学基金会NOIRLab，Gemini天文台）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of Oxford（牛津大学）；University of the Western Cape（西开普大学）；Durham University（杜伦大学）；The Pennsylvania State University（宾夕法尼亚州立大学）
研究红移1.88 < z < 3.52时射电AGN活动与莱曼α发射的联系，通过测量fAGN,radio和fLya，利用HETDEX与LOFAR数据，经完整性校正得出相关占比及变化，发现多数莱曼α发射由恒星形成驱动，两者缺乏相关性。
We present the broadband (0.5-100 keV) spectra of three heavily obscured Active Galactic Nuclei (AGNs), NGC 1106, UGC 03752, and NGC 2788A, observed with Suzaku and Swift/Burst Alert Telescope (BAT). The targets are selected from the Swift/BAT 70-month catalog on the basis of high hardness ratio between above and below 10 keV, and their X-ray spectra are reported here for the first time. We apply three models, a conventional model utilizing an analytic reflection code and two Monte-Carlo based torus models with a doughnut-like geometry (MYTorus) and with a nearly spherical geometry (Ikeda toru…
A large fraction of active galactic nuclei (AGN) are "invisible" in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared-bright AGN is predicted by models of galaxy - supermassive black hole coevolution and is required to explain the observed X-ray and infrared backgrounds. Recently, infrared colour-cuts with WISE have identified a portion of this missing population. However, as the host galaxy brightness relative to that of the AGN increases, it becomes increasingly difficult to differentiate between infrared emis…
We searched for high-z quasars within the X-ray source population detected in the contiguous $\sim 140^2$ eFEDS field observed by eROSITA during the performance verification phase. We collected the available spectroscopic information in the field, including the sample of all currently known optically selected z>5.5 quasars and cross-matched secure Legacy DR8 counterparts of eROSITA-detected X-ray point-like sources with this spectroscopic sample. We report the X-ray detection of an eROSITA source securely matched to the well-known quasar SDSS J083643.85+005453.3 (z=5.81). The soft X-ray flux o…
Low radio frequency surveys are important for testing unified models of radio-loud quasars and radio galaxies. Intrinsically similar sources that are randomly oriented on the sky will have different projected linear sizes. Measuring the projected linear sizes of these sources provides an indication of their orientation. Steep-spectrum isotropic radio emission allows for orientation-free sample selection at low radio frequencies. We use a new radio survey of the Boötes field at 150 MHz made with the Low Frequency Array (LOFAR) to select a sample of radio sources. We identify 44 radio galaxies a…
We aimed to study the molecular composition of the interstellar medium (ISM) surrounding an Active Galactic Nucleus (AGN), by making an inventory of molecular species and their abundances, as well as to establish a chemical differentiation between starburst galaxies and AGN. We used the IRAM-30 m telescope to observe the central 1.5-2 kpc region of NGC1068, covering the frequencies between 86.2 GHz and 115.6 GHz. Using Boltzmann diagrams, we calculated the column densities of the detected molecules. We used a chemical model to reproduce the abundances found in the AGN, to determine the origin …
We present spectral energy distributions (SEDs) of 69 QSOs at z>5, covering a rest frame wavelength range of 0.1mu to ~80mu, and centered on new Spitzer and Herschel observations. The detection rate of the QSOs with Spitzer is very high (97% at lambda_rest ~< 4mu), but drops towards the Herschel bands with 30% detected in PACS (rest frame mid-infrared) and 15% additionally in the SPIRE (rest frame far-infrared; FIR). We perform multi-component SED fits for Herschel-detected objects and confirm that to match the observed SEDs, a clumpy torus model needs to be complemented by a hot (~1300K) comp…
Modern cosmological simulations rely heavily on feedback from active galactic nuclei (AGN) in order to stave off overcooling in massive galaxies and galaxy groups and clusters. An important independent test is whether or not the simulations capture the broad demographics of the observed AGN population. Here, we have used the cosmo-OWLS suite of cosmological hydrodynamical simulations to produce realistic synthetic catalogs of X-ray AGN out to $z$=3, with the aim of comparing the catalogs to the observed X-ray AGN population in the XXL survey and other recent surveys. We focused on the unabsorb…
