Publications by Dimitra Rigopoulou

Herschel Observations of Far-Infrared Cooling Lines in intermediate Redshift (Ultra)-luminous Infrared Galaxies

ArXiv (0)

D Rigopoulou, R Hopwood, GE Magdis, N Thatte, BM Swinyard, D Farrah, J-S Huang, A Alonso-Herrero, JJ Bock, D Clements, A Cooray, MJ Griffin, S Oliver, C Pearson, D Riechers, D Scott, A Smith, M Vaccari, I Valtchanov, L Wang

We report the first results from a spectroscopic survey of the [CII] 158um line from a sample of intermediate redshift (0.2<z<0.8) (ultra)-luminous infrared galaxies, (U)LIRGs (LIR>10^11.5 Lsun), using the SPIRE-Fourier Transform Spectrometer (FTS) on board the Herschel Space Observatory. This is the first survey of [CII] emission, an important tracer of star-formation, at a redshift range where the star-formation rate density of the Universe increases rapidly. We detect strong [CII] 158um line emission from over 80% of the sample. We find that the [CII] line is luminous, in the range (0.8-4)x10^(-3) of the far-infrared continuum luminosity of our sources, and appears to arise from photodissociation regions on the surface of molecular clouds. The L[CII]/LIR ratio in our intermediate redshift (U)LIRGs is on average ~10 times larger than that of local ULIRGs. Furthermore, we find that the L[CII]/LIR and L[CII]/LCO(1-0) ratios in our sample are similar to those of local normal galaxies and high-z star-forming galaxies. ULIRGs at z~0.5 show many similarities to the properties of local normal and high-z star forming galaxies. Our findings strongly suggest that rapid evolution in the properties of the star forming regions of luminous infrared galaxies is likely to have occurred in the last 5 billion years.

Herschel-SPIRE-Fourier Transform Spectroscopy of the nearby spiral galaxy IC342

Monthly Notices of the Royal Astronomical Society (0)

D Rigopoulou, PD Hurley, BM Swinyard, J Virdee, KV Croxall, RHB Hopwood, T Lim, GE Magdis, CP Pearson, E Pellegrini, E Polehampton, J-D Smith

The Spitzer Extragalactic Representative Volume Survey (SERVS): survey definition and goals

ArXiv (0)

J-C Mauduit, M Lacy, D Farrah, JA Surace, M Jarvis, S Oliver, C Maraston, M Vaccari, L Marchetti, G Zeimann, EA Gonzalez-Solares, J Pforr, AO Petric, B Henriques, PA Thomas, J Afonso, A Rettura, G Wilson, JT Falder, JE Geach, M Huynh, RP Norris, N Seymour, GT Richards, SA Stanford, DM Alexander, RH Becker, PN Best, L Bizzocchi, D Bonfield, N Castro, A Cava, S Chapman, N Christopher, DL Clements, G Covone, N Dubois, JS Dunlop, E Dyke, A Edge, HC Ferguson, S Foucaud, A Franceschini, RR Gal, JK Grant, M Grossi, E Hatziminaoglou, S Hickey, JA Hodge, J-S Huang, RJ Ivison, M Kim, O LeFevre, M Lehnert, CJ Lonsdale, LM Lubin, RJ McLure, H Messias, A Martinez-Sansigre, AMJ Mortier, DM Nielsen, M Ouchi, G Parish, I Perez-Fournon, M Pierre, S Rawlings, A Readhead, SE Ridgway, D Rigopoulou, AK Romer, IG Rosebloom, HJA Rottgering, M Rowan-Robinson, A Sajina, CJ Simpson, I Smail, GK Squires, JA Stevens, R Taylor, M Trichas, T Urrutia, EV Kampen, A Verma, CK Xu

We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 square degrees medium-deep survey at 3.6 and 4.5 microns with the post-cryogenic Spitzer Space Telescope to ~2 microJy (AB=23.1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from z~5 to the present day, and is the first extragalactic survey both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z>1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this paper, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicing to catalogs, as well as coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey.

MESMER: MeerKAT Search for Molecules in the Epoch of Reionization

ArXiv (0)

I Heywood, RP Armstrong, R Booth, AJ Bunker, RP Deane, MJ Jarvis, JL Jonas, ME Jones, H-R Kloeckner, J-P Kneib, KK Knudsen, F Levrier, D Obreschkow, D Rigopoulou, S Rawlings, OM Smirnov, AC Taylor, A Verma, J Dunlop, MG Santos, ER Stanway, C Willott

[Abridged] Observations of molecular gas at all redshifts are critical for measuring the cosmic evolution in molecular gas density and understanding the star-formation history of the Universe. The 12CO molecule (J=1-0 transition = 115.27 GHz) is the best proxy for extragalactic H2, which is the gas reservoir from which star formation occurs, and has been detected out to z~6. Typically, redshifted high-J lines are observed at mm-wavelengths, the most commonly targeted systems exhibiting high SFRs (e.g. submm galaxies), and far-IR-bright QSOs. While the most luminous objects are the most readily observed, detections of more typical galaxies with modest SFRs are essential for completing the picture. ALMA will be revolutionary in terms of increasing the detection rate and pushing the sensitivity limit down to include such galaxies, however the limited FoV when observing at such high frequencies makes it difficult to use ALMA for studies of the large-scale structure traced out by molecular gas in galaxies. This article introduces a strategy for a systematic search for molecular gas during the EoR (z~7 and above), capitalizing on the fact that the J=1-0 transition of 12CO enters the upper bands of cm-wave instruments at high-z. The FoV advantage gained by observing at such frequencies, coupled with modern broadband correlators allows significant cosmological volumes to be probed on reasonable timescales. In this article we present an overview of our future observing programme which has been awarded 6,500 hours as one of the Large Survey Projects for MeerKAT, the forthcoming South African SKA pathfinder instrument. Its large FoV and correlator bandwidth, and high-sensitivity provide unprecedented survey speed for such work. An existing astrophysical simulation is coupled with instrumental considerations to demonstrate the feasibility of such observations and predict detection rates.

Ultr-Luminous Infrared Galaxies: QSOs in Formation?

ArXiv (0)

LJ Tacconi, R Genzel, D Lutz, D Rigopoulou, AJ Baker, C Iserlohe, M Tecza

We present new near-infrared Keck and VLT spectroscopic data on the stellar dynamics in late stage, ultra-luminous infrared galaxy (ULIRG) mergers . We now have information on the structural and kinematic properties of 18 ULIRGs, 8 of which contain QSO-like active galactic nuclei. The host properties (velocity dispersion, effective radius, effective surface brightness, M_K) of AGN-dominated and star formation dominated ULIRGs are similar. ULIRGs fall remarkably close to the fundamental plane of early type galaxies. They populate a wide range of the plane, are on average similar to L*-rotating ellipticals, but are well offset from giant ellipticals and optically/UV bright, low-z QSOs/radio galaxies. ULIRGs and local QSOs/radio galaxies are very similar in their distributions of bolometric and extinction corrected near-IR luminosities, but ULIRGs have smaller effective radii and velocity dispersions than the local QSO/radio galaxy population. Hence, their host masses and inferred black hole masses are correspondingly smaller. The latter are more akin to those of local Seyfert galaxies. ULIRGs thus resemble local QSOs in their near-IR and bolometric luminosities because they are (much more) efficiently forming stars and/or feeding their black holes, and not because they have QSO-like, very massive black holes. We conclude that ULIRGs as a class cannot evolve into optically bright QSOs. They will more likely become quiescent, moderate mass field ellipticals or, when active, might resemble the X-ray bright, early type galaxies that have recently been found by the Chandra Observatory.

Kinematics of Galaxies in the Hubble Deep Field South: Discovery of a Very Massive Spiral at z=0.6

ArXiv (0)

D Rigopoulou, A Franceschini, H Aussel, R Genzel, N Thatte, CJ Cesarsky

We report the first results from a study of the internal kinematics, based on spatially resolved H_alpha velocity profiles, of three galaxies at redshift z~0.6 and one at redshift z~0.8, detected by ISOCAM in the Hubble Deep Field South. The kinematics are derived from high resolution near-infrared VLT spectroscopy. One of the galaxies is a massive spiral which possesses a very large rotational velocity of 460 km/s and contains a mass of 10^12 M_solar (within 20 kpc), significantly higher than the dynamical masses measured in most other local and high redshift spirals. Two of the galaxies comprise a counter-rotating interacting system, while the fourth is also a large spiral. The observed galaxies are representative examples of the morphologies encountered among ISOCAM galaxies. The mass-to-light (M /L_bol) ratios of ISOCAM galaxies lie between those of local luminous IR galaxies and massive spirals. We measure an offset of 1.6+/-0.3 mag in the rest frame B-band and of 0.7+/-0.3 mag in the rest frame I-band when we compare the four ISOCAM galaxies to the local Tully-Fisher B and I-band relations. We conclude that the large IR luminosity of the ISOCAM population results from a combination of large mass and efficient triggering of star formation. Since ISOCAM galaxies contribute significantly to the Cosmic Infrared Background our results imply that a relatively small number of very massive and IR luminous objects contribute significantly to the IR background and star formation activity near z~0.7.

Ultra-Luminous Infrared Mergers: Elliptical Galaxies in Formation?

ArXiv (0)

R Genzel, LJ Tacconi, D Rigopoulou, D Lutz, M Tecza

We report high quality near-infrared spectroscopy of 12 ultra-luminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are 'ellipticals-in-formation'. Random motions dominate their stellar dynamics, but significant rotation is common. Gas and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution sensitive, r(eff)-sigma projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane and their distribution of v(rot)*sin(i)/sigma closely resemble those of intermediate mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas rich, disk galaxies while giant ellipticals with large cores have a different formation history.

What Powers Ultra-luminous IRAS Galaxies?

ArXiv (0)

R Genzel, D Lutz, E Sturm, E Egami, D Kunze, AFM Moorwood, D Rigopoulou, HWW Spoon, A Sternberg, LE Tacconi-Garman, L Tacconi, N Thatte

We present an ISO SWS and ISOPHOT-S, mid-infrared spectroscopic survey of 15 ultra-luminous IRAS galaxies. We combine the survey results with a detailed case study, based on near-IR and mm imaging spectroscopy, of one of the sample galaxies (UGC 5101). We compare the near- and mid-IR characteristics of these ultra-luminous galaxies to ISO and literature data of thirty starburst and active galactic nuclei (AGN), template galaxies. We find that 1) 70-80% of the ultra-luminous IRAS galaxies in our sample are predominantly powered by recently formed massive stars. 20-30% are powered by a central AGN. These conclusions are based on a new infrared 'diagnostic diagram' involving the ratio of high to low excitation mid-IR emission lines on the one hand, and on the strength of the 7.7um PAH feature on the other hand. 2) at least half of the sources probably have simultaneously an active nucleus and starburst activity in a 1-2 kpc diameter circum-nuclear disk/ring. 3) the mid-infrared emitting regions are highly obscured. After correction for these extinctions, we estimate that the star forming regions in ULIRGs have ages between 10^7 and 10^8 years, similar to but somewhat larger than those found in lower luminosity starburst galaxies. 4) in the sample we have studied there is no obvious trend for the AGN component to dominate in the most compact, and thus most advanced mergers. Instead, at any given time during the merger evolution, the time dependent compression of the circum-nuclear interstellar gas, the accretion rate onto the central black hole and the associated radiation efficiency may determine whether star formation or AGN activity dominates the luminosity of the system.

SWS observations of the galactic center


D Lutz, H Feuchtgruber, R Genzel, D Kunze, D Rigopoulou, HWW Spoon, CM Wright, E Egami, R Katterloher, E Sturm, E Wieprecht, A Sternberg, AFM Moorwood, T deGraauw

Multiwavelength energy distributions of ultraluminous IRAS galaxies .1. Submillimetre and X-ray observations


D Rigopoulou, A Lawrence, M RowanRobinson

Molecular line CO (2->1) observations of ultraluminous IRAS galaxies

ASTRONOMY & ASTROPHYSICS 305 (1996) 747-755

D Rigopoulou, A Lawrence, GJ White, M RowanRobinson, SE Church

What powers luminous infrared galaxies?


D Lutz, R Genzel, A Sternberg, H Netzer, D Kunze, D Rigopoulou, E Sturm, E Egami, H Feuchtgruber, AFM Moorwood, T deGraauw

ISO-SWS spectroscopy of Arp 220: A highly obscured starburst galaxy


E Sturm, D Lutz, R Genzel, A Sternberg, E Egami, D Kunze, D Rigopoulou, OH Bauer, H Feuchtgruber, AFM Moorwood, T deGraauw

SWS spectroscopy of the colliding galaxies NGC 4038/39


D Kunze, D Rigopoulou, D Lutz, E Egami, H Feuchtgruber, R Genzel, HWW Spoon, E Sturm, A Sternberg, AFM Moorwood, T deGraauw

SWS spectroscopy of the starburst galaxy NGC 3256


D Rigopoulou, D Lutz, R Genzel, E Egami, D Kunze, D Sturm, E Sturm, H Feuchtgruber, S Schaeidt, OH Bauer, A Sternberg, H Netzer, AFM Moorwood, T deGraauw