We present a quantitative estimate of the relative AGN/starburst content in a sample of 59 nearby (z<0.15) infrared bright ULIRGs taken from the 1 Jy sample, based on infrared L-band (3-4 micron) spectra. By using diagnostic diagrams and a simple deconvolution model, we show that at least 60% of local ULIRGs contain an active nucleus, but the AGN contribution to the bolometric luminosity is relevant only in ~15-20% of the sources. Overall, ULIRGs appear to be powered by the starburst process, responsible for >85% of the observed infrared luminosity. The subsample of sources optically classified as LINERs (31 objects) shows a similar AGN/starburst distribution as the whole sample, indicating a composite nature for this class of objects. We also show that a few ULIRGs, optically classified as starbursts, have L-band spectral features suggesting the presence of a buried AGN.
We apply a simple model, tested on local ULIRGs, to disentangle the active galactic nucleus (AGN) and starburst contributions in submillimiter and 24um-selected ULIRGs observed with the Spitzer-IRS spectrometer. We quantitatively estimate the average AGN contribution to the stacked 6-8um rest-frame spectra of these sources in different luminosity and redshift ranges, and, under the assumption of similar infrared-to-bolometric ratios as in local ULIRGs, the relative AGN/starburst contributions to the total infrared luminosity. Though the starburst component is always dominant in submillimeter-s…
It has long been thought that there is a connection between ultraluminous infrared galaxies (ULIRGs), quasars, and major mergers. Indeed, simulations show that major mergers are capable of triggering massive starbursts and quasars. However, observations by the Herschel Space Observatory suggest that, at least at high redshift, there may not always be a simple causal connection between ULIRGs and mergers. Here, we combine an evolving merger-triggered AGN luminosity function with a merger-triggered starburst model to calculate the maximum contribution of major mergers to the ULIRG population. We…
We present an optical spectroscopic study of a 90% complete sample of 17 nearby ULIRGs with optical Seyfert nuclei, with the aim of investigating the nature of the nuclear warm gas outflows. A high proportion (94%) of our sample show disturbed emission line kinematics in the form of broad (FWHM > 500 km s-1) and/or strongly blueshifted (ΔV < -150 km s-1) emission line components. This proportion is significantly higher than found in a comparison sample of non-Sy ULIRGs (19%). We also find evidence that the [OII]5007,4959 emission lines in Sy-ULIRGs are broader and more asymmetric that in sampl…
We report the results from a comprehensive study of 74 ultraluminous infrared galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within z ~ 0.3$ observed with the Spitzer Infrared Spectrograph (IRS). The contribution of nuclear activity to the bolometric luminosity in these systems is quantified using six independent methods that span a range in wavelength and give consistent results within ~ +/-10-15% on average. The average derived AGN contribution in ULIRGs is ~35-40%, ranging from ~15-35% among "cool" (f_25/f_60 =< 0.2) optically classified HII-like and LINER ULIRGs to ~50 and ~75% among …
We present a study of the optical spectral properties of 115 ultraluminous infrared galaxies (ULIRGs) in the southern sky. Using the optical spectra obtained at CTIO 4 m and provided by the 2dF Galaxy Redshift Survey and the 6dF Galaxy Survey, we measure emission line widths and fluxes for spectral classification. We determine the spectral types of ULIRGs with H_alpha measurement using the standard diagnostic diagrams. For ULIRGs without H_alpha measurement, we determine their spectral types using the plane of flux ratio between [OIII]_lambda5007 and H_beta versus [OIII] line width based on ou…
We report the discovery of blue shifted (delta(V) > 200 km/s) mid-infrared [NeIII] and/or [NeV] emission in 25 out of 82 ULIRGs (30% of our sample). The incidence of blue shifted [NeV] emission is even higher (59%) among the sources with a [NeV] detection -- the tell-tale signature of an active galactic nucleus (AGN). Sixteen ULIRGs in our sample, eleven of which are optically classified as AGN, have [NeIII] blue shifts above 200 km/s. A comparison of the line profiles of their 12.81um [NeII], 15.56um [NeIII] and 14.32um [NeV] lines reveals the ionization of the blue shifted gas to increase wi…
Ultraluminous infrared galaxies (ULIRGs) have several types according to dominance of starburst or AGN component. We made stellar population analysis for a sample of 160 ULIRGs to study the evolution of ULIRGs. We found that the dominance of intermediate-age and old stellar populations increases along the sequence of HII-like ULIRGs, Seyfert-HII composite ULIRGs, and Seyfert 2 ULIRGs. Consequently the typical mean stellar age and the stellar mass increase along the sequence. Comparing the gas mass estimated from the CO measurements with the stellar mass estimated from the optical spectra, we f…
We report on our observations of the 79 and 119um doublet transitions of OH for 24 local (z<0.262) ULIRGs observed with Herschel-PACS as part of the Herschel ULIRG Survey (HERUS). Some OH119 profiles display a clear P-Cygni shape and therefore imply outflowing OH gas, other profiles are predominantly in absorption or are completely in emission. We find that the relative strength of the OH emission component decreases as the silicate absorption increases. This locates the OH outflows inside the obscured nuclei. The maximum outflow velocities for our sources range from less than 100 to 2000 km/s…
Mass outflows driven by stars and active galactic nuclei are a key element in many current models of galaxy evolution. They may produce the observed black hole-galaxy mass relation and regulate and quench both star formation in the host galaxy and black hole accretion. However, observational evidence of such feedback processes through outflows of the bulk of the star forming molecular gas is still scarce. Here we report the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key proj…
We present a 5-8 micron analysis of the Spitzer-IRS spectra of 71 ultraluminous infrared galaxies (ULIRGs) with redshift z < 0.15, devoted to the study of the role of active galactic nuclei (AGN) and starbursts (SB) as the power source of the extreme infrared emission. Around 5 micron an AGN is much brighter (by a factor 30) than a starburst of equal bolometric luminosity. This allows us to detect the presence of even faint accretion-driven cores inside ULIRGs: signatures of AGN activity are found in 70 per cent of our sample (50/71 sources). Through a simple analytical model we are also able …
We present ultra-deep mid-IR spectra of 48 infrared-luminous galaxies in the GOODS-South field obtained with the InfraRed Spectrograph (IRS) on the Spitzer Space Telescope. These galaxies are selected among faint infrared sources (0.14 - 0.5 mJy at 24 um) in two redshift bins (0.76-1.05 and 1.75-2.4) to sample the major contributors to the cosmic infrared background at the most active epochs. We estimate redshifts for 92% of the sample using PAH and Si absorption features. Only few of these galaxies (5% at z~1 and 12% at z~2) have their total infrared luminosity dominated by emission from AGN.…
We present the X-ray analysis of the most luminous obscured active galactic nuclei (AGN) inside local ultraluminous infrared galaxies (ULIRGs). Our sample consists of ten sources, harbouring AGN components with estimated luminosity in excess of ~10^12 L_sun and yet unidentified at optical wavelengths because of their large obscuration. According to the Chandra and XMM-Newton spectra, only in two cases out of ten clear AGN signatures are detected at 2-10 keV in the shape of reflected emission. The X-ray flux from the starburst (SB) components, instead, is always broadly consistent with the expe…
We present the results of a 5-8 micron spectral analysis performed on the largest sample of local ultraluminous infrared galaxies (ULIRGs) selected so far, consisting of 164 objects up to a redshift of ~0.35. The unprecedented sensitivity of the Infrared Spectrograph onboard Spitzer allowed us to develop an effective diagnostic method to disentangle the active galactic nucleus (AGN) and starburst (SB) contribution to this class of objects. The intrinsic bolometric corrections are estimated for both the components, in order to obtain the relative AGN/SB contribution to the total luminosity of e…
The enormous amounts of infrared (IR) radiation emitted by luminous infrared galaxies (LIRGs, L_IR=10^11-10^12Lsun) and ultraluminous infrared galaxies (ULIRGs, L_IR>10^12Lsun) are produced by dust heated by intense star formation (SF) activity and/or an active galactic nucleus (AGN). The elevated star formation rates and high AGN incidence in (U)LIRGs make them ideal candidates to study the interplay between SF and AGN activity in the local universe. In this paper I review recent results on the physical extent of the SF activity, the AGN detection rate (including buried AGN), the AGN bolometr…
In this first paper on the results of our Herschel PACS survey of local Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared…
We present the first detections of the 3um water ice and 3.4um amorphous hydrocarbon (HAC) absorption features in z~2 ULIRGs. These are based on deep rest-frame 2-8um Spitzer IRS spectra of 11 sources selected for their appreciable silicate absorption. The HAC-to-silicate ratio for our z~2 sources is typically higher by a factor of 2-5 than that observed in the Milky Way. This HAC `excess' suggests compact nuclei with steep temperature gradients as opposed to predominantly host obscuration. Beside the above molecular absorption features, we detect the 3.3um PAH emission feature in one of our s…
The observed faintness of infrared fine-structure line emission along with the warm far-infrared (FIR) colors of ultraluminous infrared galaxies (ULIRGs) is a long-standing problem. In this work, we calculate the line and continuum properties of a cloud exposed to an Active Galactic Nucleus (AGN) and starburst spectral energy distribution (SED). We use an integrated modeling approach, predicting the spectrum of ionized, atomic, and molecular environments in pressure equilibrium. We find that the effects of high ratios of impinging ionizing radiation density to particle density (i.e. high ioniz…
In this paper, we characterize the infrared spectral energy distributions (SEDs) of mid-IR selected z~0.3-3.0 and L_IR~10^11-10^13Lsun galaxies, and study how their SEDs differ from those of local and high-z analogs. Our mid-IR flux-limited sample of 191 sources is unique in size, and spectral coverage, including Spitzer mid-IR spectroscopy. Here we add Herschel photometry at 250um, 350um, and 500um, which allows us to obtain accurate total IR luminosities, as well as constrain the relative contributions of AGN and starbursts to those luminosities. Our sample constitutes ~23% AGN (i.e. where t…
We apply methods from Bayesian inferencing and graph theory to a dataset of 102 mid-infrared spectra, and archival data from the optical to the millimeter, to construct an evolutionary paradigm for z<0.4 infrared-luminous galaxies (ULIRGs). We propose that the ULIRG lifecycle consists of three phases. The first phase lasts from the initial encounter until approximately coalescence. It is characterized by homogeneous mid-IR spectral shapes, and IR emission mainly from star formation, with a contribution from an AGN in some cases. At the end of this phase, a ULIRG enters one of two evolutionary …
We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Robert C. Byrd Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST) sample of ultraluminous infrared galaxies (ULIRGs; L$_{8-1000 μm} > 10^{12}$ L$_\odot$) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGN) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of HI absorption (emission) to be 100% (29%) in ULIRGs with HI detections, 10…
We analyze the link between active galactic nuclei (AGN) and mid-infrared flux using dust radiative transfer calculations of starbursts realized in hydrodynamical simulations. Focusing on the effects of galaxy dust, we evaluate diagnostics commonly used to disentangle AGN and star formation in ultraluminous infrared galaxies (ULIRGs). We examine these quantities as a function of time, viewing angle, dust model, AGN spectrum, and AGN strength in merger simulations representing two possible extremes of the ULIRG population: one is a typical gas-rich merger at z ~ 0, and the other is characterist…
We present the results of Spitzer IRS low-resolution infrared 5-35 micron spectroscopy of 17 nearby ULIRGs at z < 0.2, optically classified as non-Seyferts. The presence of optically elusive, but intrinsically luminous, buried AGNs is investigated, based on the strengths of polycyclic aromatic hydrocarbon emission and silicate dust absorption features detected in the spectra. The signatures of luminous buried AGNs, whose intrinsic luminosities range up to ~10^12 Lsun, are found in eight sources. We combine these results with those of our previous research to investigate the energy function of …
Using the Infrared Spectrograph on board the Spitzer Space Telescope, we present low-resolution (64 < lambda / dlambda < 124), mid-infrared (20-38 micron) spectra of 23 high-redshift ULIRGs detected in the Bootes field of the NOAO Deep Wide-Field Survey. All of the sources were selected to have 1) fnu(24 micron) > 0.5 mJy; 2) R-[24] > 14 Vega mag; and 3) a prominent rest-frame 1.6 micron stellar photospheric feature redshifted into Spitzer's 3-8 micron IRAC bands. Of these, 20 show emission from polycyclic aromatic hydrocarbons (PAHs), usually interpreted as signatures of star formation. The P…
We investigate the fraction of starbursts, starburst-AGN composites, Seyferts, and LINERs as a function of infrared luminosity (L_IR) and merger progress for ~500 infrared-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (< 5%) compared with other spectral types. The lack of strong infrared emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previ…
We present a stellar population synthesis study of a type I luminous infrared galaxy (LIRG): IRAS F13308+5946. It is a quasar with absolute magnitude Mi = -22.56 and has a spectral feature of a Seyfert 1.5 galaxy. Optical images show characteristics of later stages of a merger. With the help of the stellar synthesis code STARLIGHT (Cid Fernandes et al. 2005) and both Calzetti et al. (2000) and Leitherer et al.'s (2002) extinction curves, we estimate the past infrared (IR) luminosities of the host galaxy and find it may have experienced an ultraluminous infrared galaxy (ULIRG) phase for nearly …
We present a comparison of Spitzer IRS data for 51 OH megamaser (OHM) hosts and 15 non-masing ULIRGs. 10-25% of OHMs show evidence for the presence of an AGN, significantly lower than the estimated AGN fraction from previous optical and radio studies. Non-masing ULIRGs have a higher AGN fraction (50-95%) than OHMs, although some galaxies in both samples show evidence of co-existing starbursts and AGN. Radiative transfer models of the dust environment reveal that non-masing galaxies tend to have clumpy dust geometries commonly associated with AGN, while OHMs have deeper absorption consistent wi…
We discuss here a long Suzaku observation of IRAS 19254-7245 (also known as the Superantennae), one of the brightest and well studied Ultra Luminous Infrared Galaxies in the local Universe. This long observation provided the first detection of IRAS 19254-7245 above 10 keV, and measured a 15-30 keV flux of ~5x10^(-12) erg cm^-2 s^-1. The detection above 10 keV has allowed us to unveil, for the first time, the intrinsic luminosity of the AGN hosted in IRAS 19254-7245, which is strongly absorbed (Nh ~ 3x10^(24) cm^-2) and has an intrinsic luminosity in the QSO regime (L(2-10 keV) ~ 3 x 10^(44) er…
This paper is the second in a series aimed at examining the gaseous environments of z$\le$0.3 quasars and ultraluminous infrared galaxies (ULIRGs) as a function of AGN/host galaxy properties across the merger sequence. This second paper focuses on the Ly$α$ emission and O VI and N V absorption features, tracers of highly ionized gas outflows, in ULIRGs observed with HST/COS. Ly$α$ emission is detected in 15 out of 19 ULIRGs, and 12 of the 14 clear Ly$α$ detections show emission with blueshifted velocity centroids and/or wings. The equivalent widths of the Ly$α$ emission increase with increasin…
We present CO observations of 9 ULIRGs at z~2 with S(24μm)>1mJy, previously confirmed with the mid-IR spectra in the Spitzer First Look Survey. All targets are required to have accurate redshifts from Keck/GEMINI near-IR spectra. Using the Plateau de Bure millimeter-wave Interferometer (PdBI) at IRAM, we detect CO J(3-2) [7 objects] or J(2-1) [1 object] line emission from 8 sources with integrated intensities Ic ~(5-9)sigma. The CO detected sources have a variety of mid-IR spectra, including strong PAH, deep silicate absorption and power-law continuum, implying that these molecular gas rich ob…
We fit the near-infrared to radio spectral energy distributions of a sample of 30 luminous and ultra-luminous infrared galaxies with models that include both starburst and AGN components. The aim of the work was to determine important physical parameters for this kind of objects such as the optical depth towards the luminosity source, the star formation rate, the star formation efficiency and the AGN fraction. We found that although about half of our sample have best-fit models that include an AGN component, only 30 % have an AGN which accounts for more than 10 % of the infrared luminosity whe…
We present radio observations of ultraluminous infrared galaxies (ULIRGs) using the Giant Metrewave Radio Telescope (GMRT) and combine them with archival multi-frequency observations to understand whether ULIRGs are the progenitors of the powerful radio loud galaxies in the local Universe. ULIRGs are characterized by large infrared luminosities ($L_{IR}>$10$^{12}$L$\odot$), large dust masses ($\sim10^{8}M_{\odot}$) and vigorous star formation (star formation rates $\sim$10-100 $M_{\odot}~$yr$^{-1}$). Studies show that they represent the end stages of mergers of gas-rich spiral galaxies. Their …
We present the first principal component analysis (PCA) applied to a sample of 119 Spitzer Infrared Spectrograph (IRS) spectra of local ultraluminous infrared galaxies (ULIRGs) at z<0.35. The purpose of this study is to objectively and uniquely characterise the local ULIRG population using all information contained in the observed spectra. We have derived the first three principal components (PCs) from the covariance matrix of our dataset which account for over 90% of the variance. The first PC is characterised by dust temperatures and the geometry of the mix of source and dust. The second PC …
(Abridged) We present new deep VLT/FORS optical spectra with intermediate resolution and large wavelength coverage of the GPS radio source and ULIRG PKS1345+12 (4C12.50; z=0.122), taken with the aim of investigating the impact of the nuclear activity on the circumnuclear ISM. PKS1345+12 is a powerful quasar and is also the best studied case of an emission line outflow in a ULIRG. Using the density sensitive transauroral emission lines [S II]4068,4076 and [O II]7318,7319,7330,7331, we pilot a new technique to accurately model the electron density for cases in which it is not possible to use the…
The main purpose of this research was to investigate how energetic processes associated with Active Galactic Nuclei are related to those due to nuclear or circumnuclear star formation activity. Photometric and spectroscopic data were used to discriminate these processes in a sample of starburst, infrared galaxies and AGNs. Herein, we propose new diagnostic diagrams based on the 7.7 μm polycyclic aromatic hydrocarbon emission band, the L(MIR, FIR) infrared ratio and the q parameter. The diagnostic diagrams allow us to discriminate the behavior of quasars and Seyfert 1-Seyfert 2 galaxies from st…
We analyze a sample of galaxies chosen to have F24>0.5 mJy and satisfy a certain IRAC color criterion. IRS spectra yield redshifts, spectral types, and PAH luminosities, to which we add multi-wavelength broadband photometry. Stellar population modeling and IRS spectra together demonstrate that the double criteria used to select this sample have efficiently isolated massive star-forming galaxies at z~1.9. This is the first starburst-dominated ULIRG sample at high redshift with total infrared luminosity measured directly from FIR and millimeter photometry, and as such gives us the first accurate…
We present high-resolution, high-sensitivity radio images of the ultra-luminous infrared galaxy (ULIRG) IRAS 23365+3604. We performed contemporaneous observations at 1.7 and 5.0 GHz, in three epochs separated by one year from each other, with the European very long baseline interferometry Network (EVN). We also present complementary Multi-Element Radio Linked Interferometry Network (MERLIN) at 1.6 and 5.0 GHz, and archival Very Large Array (VLA) data, taken at 1.4 and 4.9 GHz. We find that the emission at ~5.0 GHz remains quite compact as seen at different resolutions, whereas at ~1.7 GHz, hig…
We report X-ray constraints for 20 of 52 high-z ULIRGs identified in the Spitzer xFLS to constrain their obscuration. Notably, decomposition of Spitzer-IRS spectra for the 52 objects already indicates that most are weak-PAH ULIRGs dominated by hot-dust continua, characteristic of AGN. Given their redshifts, they have AGN bolometric luminosities of ~1e45-1e47 erg/s comparable to powerful QSOs. This, coupled with their high IR-to-optical ratios and often significant silicate absorption, strongly argues in favor of these mid-IR objects being heavily obscured QSOs. At X-ray energies, we marginally…
The Wide-field Infrared Survey Explorer (WISE) has completed its all-sky survey at 3.4-22 micron. We merge the WISE data with optical SDSS data and provide a phenomenological characterization of mid-IR, extragalactic sources. WISE is most sensitive at 3.4micron(W1) and least at 22micron(W4). The W1 band probes massive early-type galaxies out to z\gtrsim1. This is more distant than SDSS identified early-type galaxies, consistent with the fact that 28% of 3.4micron sources have faint or no r-band counterparts (r>22.2). In contrast, 92-95% of 12 and 22micron sources have SDSS optical counterparts…
We present VLT/VIMOS-IFU emission-line spectroscopy of a volume limited sample of 18 southern ULIRGs selected with z<0.09 and dec<10. By covering a wide range of ULIRG types, this dataset provides an important set of templates for comparison with high-redshift galaxies. We employed an automated Gaussian line fitting program to decompose the emission line profiles of Halpha, [NII], [SII], and [OI] into individual components, and chart the Halpha kinematics, and the ionized gas excitations and densities. 11/18 of our galaxies show evidence for outflowing warm ionized gas with speeds between 500 …
We have identified a complete, flux-limited, (S_160>120 mJy), sample of 160 micron-selected sources from Spitzer observations of the 1-deg^2 ISO Deep Field region in the Lockman Hole. Ground-based UV, optical and near-infrared (NIR) photometry and optical spectroscopy have been used to determine colors, redshifts and masses for the complete sample of 40 galaxies. Spitzer-IRAC+MIPS photometry, supplemented by ISOPHOT data at 90 micron and 170 micron, has been used to calculate accurate total infrared luminosities, LIR(8-1000 micron), and to determine the IR luminosity function (LF) of luminous …
Ultra-luminous infrared galaxies (ULIRGs) are interesting objects with dramatic properties. Many efforts have been made to understand the physics of their luminous infrared emission and evolutionary stages. However, a large ULIRG sample is still needed to study the properties of their central black holes (BHs), the BH-host galaxy relation, and their evolution. We identified 308 ULIRGs from the Sloan Digital Sky Survey Data Release 6, and classified them into the NL ULIRGs (with only narrow emission lines) and the Type I ULIRGs (with broad emission lines). About 56% of ULIRGs in our total sampl…
We present a merger-driven evolutionary model for the production of luminous (LIRGs) and ultraluminous infrared galaxies (ULIRGs) with warm IR colours. Our results show that simulations of gas--rich major mergers including star formation, black hole growth, and feedback can produce warm (U)LIRGs. We also find that while the warm evolutionary phase is associated with increased AGN activity, star formation alone may be sufficient to produce warm IR colours. However, the transition can be suppressed entirely - even when there is a significant AGN contribution - when we assume a single-phase ISM, …
In order to examine the far-IR/radio correlation at high redshift we have studied the Spitzer 70um/far-infrared (far-IR) properties of sub-mJy radio sources from the 13^H XMM-Newton/Chandra Deep Field by redshift and galaxy type: active galactic nucleus (AGN) or star forming galaxy (SFG). We directly detect 70um counterparts (at >3sigma significance) for 22.5% (92/408) of the radio sources, while for the rest we perform stacking analysis by redshift and galaxy type. For the sources detected at 70um we find that the median and scatter of the observed flux density ratio, q70, are similar to prev…
How does the environment affect active galactic nucleus (AGN) activity? We investigated this question in an extinction-free way, by selecting 1120 infrared galaxies in the $AKARI$ North Ecliptic Pole Wide field at redshift $z$ $\leq$ 1.2. A unique feature of the $AKARI$ satellite is its continuous 9-band infrared (IR) filter coverage, providing us with an unprecedentedly large sample of IR spectral energy distributions (SEDs) of galaxies. By taking advantage of this, for the first time, we explored the AGN activity derived from SED modelling as a function of redshift, luminosity, and environme…
Hyperluminous infrared galaxies (HLIRG) are the most luminous persistent objects in the Universe. They exhibit extremely high star formation rates, and most of them seem to harbour an AGN. They are unique laboratories to investigate the most extreme star formation, and its connection to super-massive black hole growth. The AGN and SB relative contributions to the total output in these objects is still debated. Our aim is to disentangle the AGN and SB emission of a sample of thirteen HLIRG. We have studied the MIR low resolution spectra of a sample of thirteen HLIRG obtained with the IRS on boa…
We present integral field spectroscopy observations, covering the [O III]4959,5007 emission-line doublet of eight high-redshift (z=1.4-3.4) ultra-luminous infrared galaxies (ULIRGs) that host Active Galactic Nuclei (AGN) activity, including known sub-millimetre luminous galaxies (SMGs). The targets have moderate radio luminosities that are typical of high-redshift ULIRGs (L(1.4GHz)=10^(24)-10^(25)W/Hz) and therefore are not radio-loud AGN. We de-couple kinematic components due to the galaxy dynamics and mergers from those due to outflows. We find evidence in the four most luminous systems (L([…
We explore the relationship between gas, dust and star formation in a sample of 12 ultra-luminous infrared galaxies (ULIRGs) at high redshift compared to a similar sample of local galaxies. We present new CO observations and/or Spitzer mid-IR spectroscopy for 6 70 micron selected galaxies at z~1 in order to quantify the properties of the molecular gas reservoir, the contribution of an active galactic nuclei (AGN) to the mid-IR luminosity and the star formation efficiency (SFE=LIR/L'CO). The mid-IR spectra show strong polycyclic aromatic hydrocarbon (PAH) emission and our spectral decomposition…
It is thought that a class of broad absorption line (BAL) QSOs, characterised by Fe absorption features in their UV spectra (called `FeLoBALs'), could mark a transition stage between the end of an obscured starburst event and a youthful QSO beginning to shed its dust cocoon, where Fe has been injected into the interstellar medium by the starburst. To test this hypothesis we have undertaken deep SCUBA-2 850 $μ$m observations of a sample of 17 FeLoBAL QSOs with 0.89 $\leq$ z $\leq$ 2.78 and -23.31 $\leq$ M$_{B}$ $\leq$-28.50 to directly detect an excess in the thermal emission of the dust which …
