Kevin Schawinski - ETH Zurich

Kevin Schawinski
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Kevin Schawinski
ETH Zurich

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Astrophysics of Galaxies (36)
Cosmology and Nongalactic Astrophysics (15)
High Energy Astrophysical Phenomena (13)
Earth and Planetary Astrophysics (7)
Instrumentation and Methods for Astrophysics (4)
Solar and Stellar Astrophysics (3)
Physics - Physics Education (1)
Computer Science - Learning (1)
Statistics - Machine Learning (1)

Publications Authored By Kevin Schawinski

Observations of astrophysical objects such as galaxies are limited by various sources of random and systematic noise from the sky background, the optical system of the telescope and the detector used to record the data. Conventional deconvolution techniques are limited in their ability to recover features in imaging data by the Shannon-Nyquist sampling theorem. Here we train a generative adversarial network (GAN) on a sample of $4,550$ images of nearby galaxies at $0. Read More

We study the significance of mergers in the quenching of star formation in galaxies at z~1 by examining their color-mass distributions for different morphology types. We perform two-dimensional light profile fits to GOODS iz images of ~5000 galaxies and X-ray selected active galactic nucleus (AGN) hosts in the CANDELS/GOODS-north and south fields in the redshift range 0.7Read More

We consider energy budgets and radiative history of 8 fading AGN, identified from mismatch between the ionizion of very extended (>10 kpc) ionized clouds and the luminosity of the nucleus viewed directly. All show significant fading on ~50,000-year timescales. We explore the use of minimum ionizing luminosity Q derived from photoionization balance in the brightest pixels in H-alpha at each projected radius. Read More

In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the HeII~$\lambda 4685$ emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63,915 galaxies from the Sloan Digital Sky Survey Data Release 7 at $0. Read More

We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour composite images. Images in GZH were selected from various publicly-released Hubble Space Telescope Legacy programs conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to $z \sim 1$. Read More

We present quantified visual morphologies of approximately 48,000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90% of galaxies have z < 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. Read More

We investigate the observed relationship between black hole mass ($M_{\rm BH}$), bolometric luminosity ($L_{\rm bol}$), and Eddington ratio (${\lambda}_{\rm Edd}$) with optical emission line ratios ([NII] {\lambda}6583/H{\alpha}, [SII] {\lambda}{\lambda}6716,6731/H{\alpha}, [OI] {\lambda}6300/H{\alpha}, [OIII] {\lambda}5007/H{\beta}, [NeIII] {\lambda}3869/H{\beta}, and HeII {\lambda}4686/H{\beta}) of hard X-ray-selected AGN from the BAT AGN Spectroscopic Survey (BASS). We show that the [NII] {\lambda}6583/H{\alpha} ratio exhibits a significant correlation with ${\lambda}_{\rm Edd}$ ($R_{\rm Pear}$ = -0.44, $p$-value=$3\times10^{-13}$, {\sigma} = 0. Read More

We investigate the sensitivity of the colour-based quasar selection algorithm of the Sloan Digital Sky Survey to several key physical parameters of supermassive black holes (SMBHs), focusing on BH spin ($a_{\star}$) at the high BH-mass regime ($M_{BH} \geqslant10^9\, M_{\odot}$). We use a large grid of model spectral energy distribution, assuming geometrically-thin, optically-thick accretion discs, and spanning a wide range of five physical parameters: BH mass $M_{BH}$, BH spin $a_{\star}$, Eddington ratio $L / L_{Edd}$ , redshift $z$, and inclination angle $inc$. Based on the expected fluxes in the SDSS imaging ugriz bands, we find that $\sim 99. Read More

The Disk Detective citizen science project aims to find new stars with 22 micron excess emission from circumstellar dust using data from NASA's WISE mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false-positives (galaxies, background stars, interstellar matter, image artifacts, etc. Read More

Affiliations: 1Institute for Astronomy, ETH Zurich, Switzerland, 2Institute for Astronomy, ETH Zurich, Switzerland, 3Institute for Astronomy, ETH Zurich, Switzerland

We present a comprehensive method for determining stellar mass functions, and apply it to samples in the local Universe. We combine the classical 1/Vmax approach with STY, a parametric maximum likelihood method and SWML, a non-parametric maximum likelihood technique. In the parametric approach, we are assuming that the stellar mass function can be modelled by either a single or a double Schechter function and we use a likelihood ratio test to determine which model provides a better fit to the data. Read More

We present high-resolution observations of a sample of 75 K2 targets from Campaigns 1-3 using speckle interferometry on the Southern Astrophysical Research (SOAR) telescope and adaptive optics (AO) imaging at the Keck II telescope. The median SOAR $I$-band and Keck $K_s$-band detection limits at 1" were $\Delta m_{I}=4.4$~mag and $\Delta m_{K_s}=6. Read More

We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN ($L_{\rm bol} \sim 10^{42}-10^{44}$ erg s$^{-1}$). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN ($\mbox{E$_{\rm bub}$} \sim 10^{54} - 10^{55}$ erg). Read More

We present new Keck/MOSFIRE K-band spectroscopy for a sample of 14 faint, X-ray-selected active galactic nuclei (AGNs) in the COSMOS field. The data cover the spectral region surrounding the broad Balmer emission lines, which enables the estimation of black hole masses (M_BH) and accretion rates (in terms of L/L_Edd). We focus on 10 AGN at z~3. Read More

Capitalizing on the all-sky coverage of {\it WISE}, and the 35\% and 50\% sky coverage from SDSS and Pan-STARRS, respectively, we explore the efficacy of $m_{R}$ (optical) - $m_{3.4 \mu m}$ (mid-infrared), hereafter $R-W1$, as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the $\sim$16. Read More

We investigated AGN activity in low-mass galaxies, an important regime that can shed light onto BH formation and evolution, and their interaction with their host galaxies. We identified 336 AGN candidates from a parent sample of $\sim 48,000$ nearby low-mass galaxies ($M_{\rm \star} \leq 10^{9.5}M_\odot$, $z < 0. Read More

We investigate the relationship between X-ray and optical line emission in 340 nearby AGN selected above 10 keV using Swift BAT. We find a weak correlation between the extinction corrected [O III] and hard X-ray luminosity (14-195 keV) with a [OIII] large scatter (R_Pear = 0.64, sigma = 0. Read More

We investigate a scenario in which feedback from black-hole X-ray binaries (BHXBs) sometimes begins inside young star clusters before strong supernova feedback. Those BHXBs could reduce the gas fraction inside embedded young clusters whilst maintaining virial equilibrium, which may help globular clusters (GCs) to stay bound when supernova-driven gas ejection subsequently occurs. Adopting a simple toy model with parameters guided by BHXB population models, we produce GC formation efficiencies consistent with empirically-inferred values. Read More

We present a multi-wavelength study of a newly discovered compact group (CG), SDSS J0959+1259, based data from XMM-Newton, SDSS and the Calar Alto optical imager BUSCA. With a maximum velocity offset of 500 km s$^{-1}$, a mean redshift of 0.035, and a mean spatial extension of 480 kpc, this CG is exceptional in having the highest concentration of nuclear activity in the local Universe, established with a sensitivity limit L$_{X}>4\times $10$^{40}$ erg s$^{-1}$ in 2--10 keV band and R-band magnitude $M_R < -19$. Read More

Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. Read More

We present an observational constraint for the typical active galactic nucleus (AGN) phase lifetime. The argument is based on the time lag between an AGN central engine switching on and becoming visible in X-rays, and the time the AGN then requires to photoionize a large fraction of the host galaxy. Based on the typical light travel time across massive galaxies, and the observed fraction of X-ray selected AGN without AGN-photoionized narrow lines, we estimate that the AGN phase typically lasts $\sim10^{5}$ years. Read More

We have newly identified a substantial number of type 1 active galactic nuclei (AGN) featuring weak broad-line regions (BLRs) at z < 0.2 from detailed analysis of galaxy spectra in the Sloan Digital Sky Survey Data Release 7. These objects predominantly show a stellar continuum but also a broad H-alpha emission line, indicating the presence of a low-luminosity AGN oriented so that we are viewing the central engine directly without significant obscuration. Read More

Affiliations: 1Middlebury College, 2Oxford University, 3Middlebury College, 4ETH Zurich, 5Yale University, 6NRAO Charlottesville

We used the Hubble Space Telescope WFC3 near-infrared camera to image the host galaxies of a sample of eleven luminous, dust-reddened quasars at z ~ 2 -- the peak epoch of black hole growth and star formation in the Universe -- to test the merger-driven picture for the co-evolution of galaxies and their nuclear black holes. The red quasars come from the FIRST+2MASS red quasar survey and a newer, deeper, UKIDSS+FIRST sample. These dust-reddened quasars are the most intrinsically luminous quasars in the Universe at all redshifts, and may represent the dust-clearing transitional phase in the merger-driven black hole growth scenario. Read More

We combine a large, homogeneous sample of $\sim$3000 local mergers with the Imperial IRAS Faint Source Redshift Catalogue (IIFSCz), to perform a blind far-infrared (FIR) study of the local merger population. The IRAS-detected mergers are mostly ($98\%$) spiral-spiral systems, residing in low density environments, a median FIR luminosity of $10^{11} L_\odot$ (which translates to a median star formation rate of around 15$M_\odot yr^{-1}$). The FIR luminosity -- and therefore the star formation rate -- shows little correlation with group richness and scales with the total stellar mass of the system, with little or no dependence on the merger mass ratio. Read More

We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z<0.085, using Galaxy~Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disk, and show that both the slope and dispersion of the M-SFR relation is constant when varying all the above parameters. Read More

We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19,756 disc galaxies at $0.01Read More

Affiliations: 1Institute for Astronomy, ETH Zürich, 2Institute for Astronomy, ETH Zürich, 3Departamento de Astronomía, Universidad de Concepción, 4Physics Department and Yale Center for Astronomy and Astrophysics, Yale University, 5Institute for Astronomy, ETH Zürich, 6Institute for Astronomy, ETH Zürich

We investigate early black hole (BH) growth through the methodical search for $z\gtrsim5$ AGN in the $Chandra$ Deep Field South. We base our search on the $Chandra$ 4-Ms data with flux limits of $9.1\times\ 10^{-18}$ (soft, 0. Read More

The relationship between galaxy star formation rates (SFR) and stellar masses ($M_\ast$) is re-examined using a mass-selected sample of $\sim$62,000 star-forming galaxies at $z \le 1.3$ in the COSMOS 2-deg$^2$ field. Using new far-infrared photometry from $Herschel$-PACS and SPIRE and $Spitzer$-MIPS 24 $\mu$m, along with derived infrared luminosities from the NRK method based on galaxies' locations in the restframe color-color diagram $(NUV - r)$ vs. Read More

We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 < z < 1. Read More

The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1. Read More

We present narrow- and medium-band HST imaging, with additional supporting ground-based data, for 8 galaxies identified as hosting fading AGN. These have AGN-ionized gas projected >10 kpc from the nucleus, and significant shortfall of ionizing radiation between the distant gas and the AGN, indicating fading AGN on ~50,000-year timescales. Every system shows evidence of ongoing or past interactions; a similar sample of obscured AGN with extended ionized clouds shares this incidence of disturbances. Read More

Limited studies have been performed on the radio-loud fraction in X-ray selected type 1 AGN samples. The consistency between various radio-loudness definitions also needs to be checked. We measure the radio-loudness of the 407 type 1 AGNs in the XMM-COSMOS quasar sample using nine criteria from the literature (six defined in the rest-frame and three defined in the observed frame): $R_L=\log(L_{5GHz}/L_B)$, $q_{24}=\log(L_{24\mu m}/L_{1. Read More

We present the results of a pilot XMM-$Newton$ and $Chandra$ program aimed at studying the diffuse intragroup medium (DIM) of optically-selected nearby groups from the Zurinch ENvironmental Study (ZENS) catalog. The groups are in a narrow mass range about $10^{13}M_\odot$, a mass scale at which the interplay between the DIM and the group member galaxies is still largely unprobed. X-ray emission from the DIM is detected in the energy band 0. Read More

We use SDSS+\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disk to spheroid and star formation is quenched rapidly. Read More

While performing a survey to detect recoiling supermassive black holes, we have identified an unusual source having a projected offset of 800 pc from a nearby dwarf galaxy. The object, SDSS J113323.97+550415. Read More

We measure the redshift evolution of the bar fraction in a sample of 2380 visually selected disc galaxies found in Cosmic Evolution Survey (COSMOS) Hubble Space Telescope (HST) images. The visual classifications used to identify both the disc sample and to indicate the presence of stellar bars were provided by citizen scientists via the Galaxy Zoo: Hubble (GZH) project. We find that the overall bar fraction decreases by a factor of two, from 22+/-5% at z=0. Read More

(Abridged) The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use GALEX, XMM Optical Monitor, and HST data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with candidates provided by Galaxy Zoo participants. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. Read More

We report the discovery of 14 new transiting planet candidates in the Kepler field from the Planet Hunters citizen science program. None of these candidates overlapped with Kepler Objects of Interest (KOIs) at the time of submission. We report the discovery of one more addition to the six planet candidate system around KOI-351, making it the only seven planet candidate system from Kepler. Read More

In this paper, we use the Galaxy Zoo 2 dataset to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR), and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of $23.6\pm 0. Read More

Affiliations: 1University of Minnesota, 2University of Oxford, 3University of Nottingham, 4University of Portsmouth, 5University of Oxford, 6Universitat de Barcelona, 7University of Portsmouth, 8University of Minnesota, 9University of Oxford, 10University of Alabama, 11University of Portsmouth, 12University of Portsmouth, 13Johns Hopkins University, 14ETH Zurich, 15University of Oxford, 16University of California San Diego, 17Adler Planetarium, 18University of Portsmouth

We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304,122 galaxies drawn from the Sloan Digital Sky Survey. Morphology is a powerful probe for quantifying a galaxy's dynamical history; however, automatic classifications of morphology (either by computer analysis of images or by using other physical parameters as proxies) still have drawbacks when compared to visual inspection. The large number of images available in current surveys makes visual inspection of each galaxy impractical for individual astronomers. Read More

Authors: Kirpal Nandra1, Didier Barret2, Xavier Barcons3, Andy Fabian4, Jan-Willem den Herder5, Luigi Piro6, Mike Watson7, Christophe Adami8, James Aird9, Jose Manuel Afonso10, Dave Alexander11, Costanza Argiroffi12, Lorenzo Amati13, Monique Arnaud14, Jean-Luc Atteia15, Marc Audard16, Carles Badenes17, Jean Ballet18, Lucia Ballo19, Aya Bamba20, Anil Bhardwaj21, Elia Stefano Battistelli22, Werner Becker23, Michaël De Becker24, Ehud Behar25, Stefano Bianchi26, Veronica Biffi27, Laura Bîrzan28, Fabrizio Bocchino29, Slavko Bogdanov30, Laurence Boirin31, Thomas Boller32, Stefano Borgani33, Katharina Borm34, Nicolas Bouché35, Hervé Bourdin36, Richard Bower37, Valentina Braito38, Enzo Branchini39, Graziella Branduardi-Raymont40, Joel Bregman41, Laura Brenneman42, Murray Brightman43, Marcus Brüggen44, Johannes Buchner45, Esra Bulbul46, Marcella Brusa47, Michal Bursa48, Alessandro Caccianiga49, Ed Cackett50, Sergio Campana51, Nico Cappelluti52, Massimo Cappi53, Francisco Carrera54, Maite Ceballos55, Finn Christensen56, You-Hua Chu57, Eugene Churazov58, Nicolas Clerc59, Stephane Corbel60, Amalia Corral61, Andrea Comastri62, Elisa Costantini63, Judith Croston64, Mauro Dadina65, Antonino D'Ai66, Anne Decourchelle67, Roberto Della Ceca68, Konrad Dennerl69, Klaus Dolag70, Chris Done71, Michal Dovciak72, Jeremy Drake73, Dominique Eckert74, Alastair Edge75, Stefano Ettori76, Yuichiro Ezoe77, Eric Feigelson78, Rob Fender79, Chiara Feruglio80, Alexis Finoguenov81, Fabrizio Fiore82, Massimiliano Galeazzi83, Sarah Gallagher84, Poshak Gandhi85, Massimo Gaspari86, Fabio Gastaldello87, Antonis Georgakakis88, Ioannis Georgantopoulos89, Marat Gilfanov90, Myriam Gitti91, Randy Gladstone92, Rene Goosmann93, Eric Gosset94, Nicolas Grosso95, Manuel Guedel96, Martin Guerrero97, Frank Haberl98, Martin Hardcastle99, Sebastian Heinz100, Almudena Alonso Herrero101, Anthony Hervé102, Mats Holmstrom103, Kazushi Iwasawa104, Peter Jonker105, Jelle Kaastra106, Erin Kara107, Vladimir Karas108, Joel Kastner109, Andrew King110, Daria Kosenko111, Dimita Koutroumpa112, Ralph Kraft113, Ingo Kreykenbohm114, Rosine Lallement115, Giorgio Lanzuisi116, J. Lee117, Marianne Lemoine-Goumard118, Andrew Lobban119, Giuseppe Lodato120, Lorenzo Lovisari121, Simone Lotti122, Ian McCharthy123, Brian McNamara124, Antonio Maggio125, Roberto Maiolino126, Barbara De Marco127, Domitilla de Martino128, Silvia Mateos129, Giorgio Matt130, Ben Maughan131, Pasquale Mazzotta132, Mariano Mendez133, Andrea Merloni134, Giuseppina Micela135, Marco Miceli136, Robert Mignani137, Jon Miller138, Giovanni Miniutti139, Silvano Molendi140, Rodolfo Montez141, Alberto Moretti142, Christian Motch143, Yaël Nazé144, Jukka Nevalainen145, Fabrizio Nicastro146, Paul Nulsen147, Takaya Ohashi148, Paul O'Brien149, Julian Osborne150, Lida Oskinova151, Florian Pacaud152, Frederik Paerels153, Mat Page154, Iossif Papadakis155, Giovanni Pareschi156, Robert Petre157, Pierre-Olivier Petrucci158, Enrico Piconcelli159, Ignazio Pillitteri160, C. Pinto161, Jelle de Plaa162, Etienne Pointecouteau163, Trevor Ponman164, Gabriele Ponti165, Delphine Porquet166, Ken Pounds167, Gabriel Pratt168, Peter Predehl169, Daniel Proga170, Dimitrios Psaltis171, David Rafferty172, Miriam Ramos-Ceja173, Piero Ranalli174, Elena Rasia175, Arne Rau176, Gregor Rauw177, Nanda Rea178, Andy Read179, James Reeves180, Thomas Reiprich181, Matthieu Renaud182, Chris Reynolds183, Guido Risaliti184, Jerome Rodriguez185, Paola Rodriguez Hidalgo186, Mauro Roncarelli187, David Rosario188, Mariachiara Rossetti189, Agata Rozanska190, Emmanouil Rovilos191, Ruben Salvaterra192, Mara Salvato193, Tiziana Di Salvo194, Jeremy Sanders195, Jorge Sanz-Forcada196, Kevin Schawinski197, Joop Schaye198, Axel Schwope199, Salvatore Sciortino200, Paola Severgnini201, Francesco Shankar202, Debora Sijacki203, Stuart Sim204, Christian Schmid205, Randall Smith206, Andrew Steiner207, Beate Stelzer208, Gordon Stewart209, Tod Strohmayer210, Lothar Strüder211, Ming Sun212, Yoh Takei213, V. Tatischeff214, Andreas Tiengo215, Francesco Tombesi216, Ginevra Trinchieri217, T. G. Tsuru218, Asif Ud-Doula219, Eugenio Ursino220, Lynne Valencic221, Eros Vanzella222, Simon Vaughan223, Cristian Vignali224, Jacco Vink225, Fabio Vito226, Marta Volonteri227, Daniel Wang228, Natalie Webb229, Richard Willingale230, Joern Wilms231, Michael Wise232, Diana Worrall233, Andrew Young234, Luca Zampieri235, Jean In't Zand236, Silvia Zane237, Andreas Zezas238, Yuying Zhang239, Irina Zhuravleva240
Affiliations: 1DE, 2FR, 3ES, 4UK, 5NL, 6IT, 7UK, 8FR, 9UK, 10PT, 11UK, 12IT, 13IT, 14FR, 15FR, 16CH, 17US, 18FR, 19IT, 20JP, 21IN, 22IT, 23DE, 24BE, 25IL, 26IT, 27IT, 28NL, 29IT, 30US, 31FR, 32DE, 33IT, 34DE, 35FR, 36IT, 37UK, 38IT, 39IT, 40UK, 41US, 42US, 43DE, 44DE, 45DE, 46US, 47IT, 48CZ, 49IT, 50US, 51IT, 52IT, 53IT, 54ES, 55ES, 56DK, 57US, 58DE, 59DE, 60FR, 61GR, 62IT, 63NL, 64UK, 65IT, 66IT, 67FR, 68IT, 69DE, 70DE, 71UK, 72CZ, 73US, 74CH, 75UK, 76IT, 77JP, 78US, 79UK, 80FR, 81FI, 82IT, 83IT, 84CA, 85UK, 86IT, 87IT, 88DE, 89GR, 90DE, 91IT, 92US, 93FR, 94BE, 95FR, 96AT, 97ES, 98DE, 99UK, 100US, 101ES, 102FR, 103SE, 104ES, 105NL, 106NL, 107UK, 108CZ, 109US, 110UK, 111FR, 112FR, 113US, 114D, 115FR, 116GR, 117US, 118FR, 119UK, 120IT, 121DE, 122IT, 123UK, 124CA, 125IT, 126UK, 127DE, 128IT, 129ES, 130IT, 131UK, 132IT, 133NL, 134DE, 135IT, 136IT, 137IT, 138US, 139ES, 140IT, 141ES, 142IT, 143FR, 144BE, 145FI, 146IT, 147US, 148JP, 149UK, 150UK, 151DE, 152DE, 153US, 154UK, 155GR, 156IT, 157US, 158FR, 159IT, 160IT, 161UK, 162NL, 163FR, 164UK, 165DE, 166FR, 167UK, 168FR, 169DE, 170US, 171US, 172NL, 173DE, 174IT, 175US, 176DE, 177BE, 178IT, 179UK, 180UK, 181DE, 182FR, 183US, 184IT, 185FR, 186CA, 187IT, 188DE, 189IT, 190PL, 191UK, 192IT, 193DE, 194IT, 195DE, 196ES, 197CH, 198NL, 199D, 200IT, 201IT, 202FR, 203UK, 204IE, 205DE, 206US, 207US, 208IT, 209UK, 210US, 211DE, 212US, 213JP, 214FR, 215IT, 216US, 217IT, 218JP, 219US, 220NL, 221US, 222IT, 223UK, 224IT, 225NL, 226IT, 227FR, 228US, 229FR, 230UK, 231DE, 232NL, 233UK, 234UK, 235IT, 236NL, 237UK, 238GR, 239DE, 240US

This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Read More

A crucial challenge in astrophysics over the coming decades will be to understand the origins of supermassive black holes (SMBHs) that lie at the centres of most, if not all, galaxies. The processes responsible for the initial formation of these SMBHs and their early growth via accretion - when they are seen as Active Galactic Nuclei (AGN) - remain unknown. To address this challenge, we must identify low luminosity and obscured z>6 AGNs, which represent the bulk of early SMBH growth. Read More

Citizen science, in which volunteers work with professional scientists to conduct research, is expanding due to large online datasets. To plan projects, it is important to understand volunteers' motivations for participating. This paper analyzes results from an online survey of nearly 11,000 volunteers in Galaxy Zoo, an astronomy citizen science project. Read More

Analysis of galaxies with overlapping images offers a direct way to probe the distribution of dust extinction and its effects on the background light. We present a catalog of 1990 such galaxy pairs selected from the Sloan Digital Sky Survey (SDSS) by volunteers of the Galaxy Zoo project. We highlight subsamples which are particularly useful for retrieving such properties of the dust distribution as UV extinction, the extent perpendicular to the disk plane, and extinction in the inner parts of disks. Read More

We compute black hole masses and bolometric luminosities for 57 active galactic nuclei (AGN) in the redshift range 1.25 < z < 2.67, selected from the GOODS-South deep multi-wavelength survey field via their X-ray emission. Read More