Villanueva de la Cañada, Spain
Villanueva de la Cañada, Spain

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Smail I.,Durham University | Geach J.E.,University of Hertfordshire | Swinbank A.M.,Durham University | Tadaki K.,Japan National Astronomical Observatory | And 24 more authors.
Astrophysical Journal | Year: 2014

We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3-0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳1012 L and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit ALMA submillimeter continuum observations, which cover one of these sources, to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalized sense) than clusters at z 0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z = 1.6, MH -23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z 1.6 (MH -20.5 and MH -21.5, respectively, at z 0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z = 1.6 and that in Cl 0218.3-0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure. © 2014. The American Astronomical Society. All rights reserved..

Geach J.E.,University of Hertfordshire | Bower R.G.,Durham University | Alexander D.M.,Durham University | Blain A.W.,University of Leicester | And 17 more authors.
Astrophysical Journal | Year: 2014

We report the detection at 850 μm of the central source in SSA22-LAB1, the archetypal "Lyman-α Blob" (LAB), a 100 kpc scale radio-quiet emission-line nebula at z = 3.1. The flux density of the source, S 850= 4.6 ± 1.1 mJy, implies the presence of a galaxy or group of galaxies with a total luminosity of L IR≈ 1012L O. The position of an active source at the center of a ∼50 kpc radius ring of linearly polarized Lyα emission detected by Hayes et al. suggests that the central source is leaking Lyα photons preferentially in the plane of the sky, which undergo scattering in H I clouds at a large galactocentric radius. The Lyα morphology around the submillimeter detection is reminiscent of a biconical outflow, and the average Lyα line profiles of the two "lobes" are dominated by a red peak, which is expected for a resonant line emerging from a medium with a bulk velocity gradient that is outflowing relative to the line center. Taken together, these observations provide compelling evidence that the central active galaxy (or galaxies) is responsible for a large fraction of the extended Lyα emission and morphology. Less clear is the history of the cold gas in the circumgalactic medium being traced by Lyα: is it mainly pristine material accreting into the halo that has not yet been processed through an interstellar medium (ISM), now being blown back as it encounters an outflow, or does it mainly comprise gas that has been swept-up within the ISM and expelled from the galaxy? © 2014. The American Astronomical Society. All rights reserved..

Saxton R.D.,XMM SOC | Read A.M.,University of Leicester | Komossa S.,Max Planck Institute for Radio Astronomy | Rodriguez-Pascual P.,XMM SOC | And 6 more authors.
Astronomy and Astrophysics | Year: 2014

Aims. New high variability extragalactic sources may be identified by comparing the flux of sources seen in the XMM-Newton Slew Survey with detections and upper limits from the ROSAT All Sky Survey.Methods. A detected flaring extragalactic source was monitored with Swift and XMM-Newton to track its temporal and spectral evolution. Optical and radio observations were made to help classify the galaxy, investigate the reaction of circumnuclear material to the X-ray flare, and check for the presence of a jet.Results. In November 2012, X-ray emission was detected from the galaxy XMMSL1 J061927.1-655311 (a.k.a. 2MASX 06192755-6553079), a factor 140 times higher than an upper limit from 20 years earlier. Both the X-ray and UV flux subsequently fell over the following year by factors of 20 and 4, respectively. Optically, the galaxy appears to be a Seyfert I with broad Balmer lines and weak, narrow, low-ionisation emission lines, at a redshift of 0.0729. The X-ray luminosity peaks at LX ∼ 8 × 1043 erg s-1 with a typical Sy I-like power-law X-ray spectrum of Γ ∼ 2. The flare has either been caused by a tidal disruption event or by an increase in the accretion rate of a persistent active galactic nucleus. © 2014 ESO.

Matthews T.G.,The Interdisciplinary Center | Ade P.A.R.,University of Cardiff | Angile F.E.,University of Pennsylvania | Benton S.J.,University of Toronto | And 29 more authors.
Astrophysical Journal | Year: 2014

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li. © 2014. The American Astronomical Society. All rights reserved..

Read A.M.,University of Leicester | Rosen S.R.,University of Leicester | Saxton R.D.,XMM SOC | Ramirez J.,Leibniz Institute for Astrophysics Potsdam
Astronomy and Astrophysics | Year: 2011

Aims. We describe here a new full 2D parameterization of the PSFs of the three XMM-Newton EPIC telescopes as a function of instrument, energy, off-axis angle and azimuthal angle, covering the whole field-of-view (FoV) of the three EPIC detectors. It models the general PSF envelopes, the primary and secondary spokes, their radial dependencies, and the large-scale azimuthal variations. Methods. This PSF model has been constructed via the stacking and centering of a large number of bright, but not significantly piled-up point sources from the full FoV of each EPIC detector, and azimuthally filtering the resultant PSF envelopes to form the spoke structures and the gross azimuthal shapes observed. Results. This PSF model is available for use within the XMM-Newton science analysis system via the usage of current calibration files XRTi-XPSF-0011.CCF and later versions. Initial source-searching tests showed substantial reductions in the numbers of spurious sources being detected in the wings of bright point sources. Furthermore, we have uncovered a systematic error in the previous PSF system, affecting the entire mission to date, whereby returned source RA and Dec values are seen to vary sinusoidally about the true position (amplitude ≈≈0.8″″) with source azimuthal position. Conclusions. The new PSF system is now available and is seen as a major improvement with regard to the detection of spurious sources. The new PSF also largely removes the discovered astrometry error and is seen to improve the positional accuracy of EPIC. The modular nature of the PSF system allows for further refinements in the future. © 2011 ESO.

Saxton R.D.,XMM SOC | Read A.M.,University of Leicester | Esquej P.,University of Leicester | Komossa S.,TU Munich | And 8 more authors.
Astronomy and Astrophysics | Year: 2012

Aims. The study of tidal disruption flares from galactic nuclei has historically been hampered by a lack of high quality spectral observations taken around the peak of the outburst. Here we introduce the first results from a program designed to identify tidal disruption events at their peak by making near-real-time comparisons of the flux seen in XMM-Newton slew sources with that seen in ROSAT. Methods. Flaring extragalactic sources, which do not appear to be AGN, are monitored with Swift and XMM-Newton to track their temporal and spectral evolution. Timely optical observations are made to monitor the reaction of circumnuclear material to the X-ray flare. Results. SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to L X ∼ 3 × 10 44 erg s -1. It has the optical spectrum of a quiescent galaxy (z = 0.146). Overall the X-ray flux has evolved consistently with the canonical t -5/3 model, expected for returning stellar debris, fading by a factor ∼300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event. © 2012 ESO.

Agis-Gonzalez B.,CSIC - National Institute of Aerospace Technology | Miniutti G.,CSIC - National Institute of Aerospace Technology | Kara E.,Institute of Astronomy | Fabian A.C.,Institute of Astronomy | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We report results from multi-epoch X-ray observations of the Seyfert 1.5 galaxyESO362-G18 performed between 2005 November and 2010 June. ESO 362-G18 generally exhibits the typical X-ray spectrum of type 1 active galactic nuclei. A disc-reflection component accounts for broad residuals in the iron K band and above 10 keV, as well as for a significant soft excess. From our best-fitting reflection model, we measure a black hole spin a ≥ 0.92 at the 99.99 per cent confidence level. ESO 362-G18 is also (typically) mildly absorbed by a column of neutral gas. The absorber is variable and one observation, performed ~2 months after a typical mildly absorbed one, is heavily absorbed by a cold column density of ~3-4 × 1023 cm-2, nearly two orders of magnitude higher than that during any other observation. UV variability between the heavily absorbed observation and the others suggests that the absorber can be identified with a dusty, clumpy torus. The absorption variability time-scale enables us to locate the X-ray-emitting region within the innermost ~50 gravitational radii. Such result holds not only for the X-ray continuum, but also for the soft excess. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Miniutti G.,CSIC - National Institute of Aerospace Technology | Saxton R.D.,XMM SOC | Rodriguez-Pascual P.M.,XMM SOC | Read A.M.,University of Leicester | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

A bright, soft X-ray source was detected on 2010 July 14 during an XMM-Newton slew at a position consistent with the galaxy GSN 069 (z = 0.018). Previous ROSAT observations failed to detect the source and imply that GSN 069 is now ≥240 times brighter than it was in 1994 in the soft X-ray band. Optical spectra (from 2001 to 2003) are dominated by unresolved emission lines with no broad components, classifying GSN 069 as a Seyfert 2 galaxy. We report here results from a ~1 yr monitoring with Swift and XMM-Newton, as well as from new optical spectroscopy. GSN 069 is an unabsorbed, ultrasoft source in X-rays, with no flux detected above ~1 keV. The soft X-rays exhibit significant variability down to time-scales of hundreds of seconds. The UV-to-X-ray spectrum of GSN 069 is consistent with a pure accretion disc model which implies an Eddington ratio λ ≃ 0.5 and a black hole mass of ≃ 1.2 × 106Mȯ. A new optical spectrum, obtained ~3.5 months after the XMM-Newton slew detection, is consistent with earlier spectra and lacks any broad-line component. The lack of cold X-ray absorption and the short time-scale variability in the soft X-rays rule out a standard Seyfert 2 interpretation of the source. The present Eddington ratio of GSN 069 exceeds the critical value below which no emitting broad-line region (BLR) forms, according to popular models, so that GSN 069 can be classified as a bona-fide high Eddington-ratio true Seyfert 2 galaxy. We discuss our results within the framework of two possible scenarios for the BLR in AGN, namely the two-phase model (cold BLR clouds in pressure equilibrium with a hotter medium), and models in which the BLR is part of an outflow, or disc-wind. Finally, we point out that GSN 069 may be a member of a population of super-soft active galactic nuclei (AGN) whose spectral energy distribution is completely dominated by accretion disc emission, as it is the case in some black hole X-ray binary transients during their outburst evolution. The disc emission for a typical AGN with black hole mass of 107-108Mȯ does not enters the soft X-ray band, so that GSN 069-like objects with larger black hole mass (i.e. the bulk of the AGN population) are missed by current X-ray surveys, or misclassified as Compton-thick candidates. If the analogy between black hole X-ray binary transients and AGN holds, the lifetime of these super-soft states inAGNmay be longer than 104 years, implying that the actual population of super-soft AGN may not be negligible, possibly contaminating the estimated fraction of heavily obscured AGN from current X-ray surveys.

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