A. J. Baker

SPITZER QUASAR AND ULIRG EVOLUTION STUDY (QUEST). I. THE ORIGIN OF THE FAR-INFRARED CONTINUUM OF QSOs

This paper addresses the origin of the far-infrared (FIR) continuum of QSOs, based on the Quasar and ULIRG Evolution Study (QUEST) of nearby QSOs and ULIRGs using observations with the Spitzer Space Telescope. For 27 Palomar-Green QSOs at z ≲ 0.3, we derive luminosities of diagnostic lines ([Ne II] 12.8 μm, [Ne V] 14.3 μm, [O IV] 25.9 μm) and emission features (PAH 7.7 μm emission, which is related to star formation), as well as continuum luminosities over a range of mid- to far-infrared wavelengths between 6 and 60 μm. We detect star-formation-related PAH emission in 11/26 QSOs and fine-structure line emission in all of them, often in multiple lines. The detection of PAHs in the average spectrum of sources that lack individual PAH detections provides further evidence for the widespread presence of PAHs in QSOs. Similar PAH/FIR and [Ne II]/FIR ratios are found in QSOs and in starburst-dominated ULIRGs and lower luminosity starbursts. We conclude that the typical QSO in our sample has at least 30% but likely most of the far-infrared luminosity (~10^(10)-10^(12) L_☉) arising from star formation, with a tendency for larger star formation contribution at the largest FIR luminosities. In the QSO sample, we find correlations between most of the quantities studied including combinations of AGN tracers and starburst tracers. The common scaling of AGN and starburst luminosities (and fluxes) is evidence for a starburst-AGN connection in luminous AGN. Strong correlations of far-infrared continuum and starburst related quantities (PAH, low-excitation [Ne II]) offer additional support for the starburst origin of far-infrared emission.

Ultraluminous Infrared Galaxies: QSOs in Formation?

We present new near-infrared (NIR) Keck and Very Large Telescope (VLT) spectroscopic data on the stellar dynamics in late-stage, ultraluminous infrared galaxy (ULIRG) mergers. We now have information on the structural and kinematic properties of 18 ULIRGs, eight of which contain QSO-like active galactic nuclei (AGNs). The host properties (σ, reff, μeff, MK) 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 NIR 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 NIR 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.

Molecular gas in NUclei of GAlaxies (NUGA). I. The counter-rotating LINER NGC 4826

This paper has been partially funded by the Spanish MCyT under projects DGES/AYA2000-927, ESP2001-4519-PE and ESP2002-01693, and European FEDER funds.

Mid-Infrared spectroscopy of two luminous submillimeter galaxies at z ~ 2.8

Using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, we have obtained rest-frame mid-infrared spectroscopy of two bright submillimeter galaxies. SMM J02399-0136 at z = 2.81 shows a superposition of polycyclic aromatic hydrocarbon (PAH) emission features and a mid-infrared continuum, indicating significant and roughly equal contributions to its bolometric luminosity from star formation and from a Compton-thick active galactic nucleus. We derive a new redshift of z = 2.80 for MM J154127+6616 from the IRS spectrum and find this object is dominated by starburst PAH emission. The rest-frame mid- to far-infrared spectral energy distributions are consistent with these submillimeter galaxies being scaled-up versions of local ultraluminous infrared galaxies. The mid-infrared spectra support the scenario that submillimeter galaxies are sites of extreme star formation and represent a key phase in the formation of massive galaxies.

SPIFFI Observations of the Starburst SMM J14011+0252:Already Old, Fat, and Rich by z = 2.565

Using the SPectrometer for Infrared Faint Field Imaging on the ESO Very Large Telescope, we have obtained J-, H-, and K-band integral field spectroscopy of the luminous submillimeter galaxy SMM J140110252. z p 2.565 A global spectrum reveals the brighter of this spatially resolved system’s two components as an intense starburst that is remarkably old, massive, and metal-rich for the early epoch at which it is observed. We see a strong Balmer break implying a ≥100 Myr timescale for continuous star formation as well as nebular emission-line ratios implying a supersolar oxygen abundance on large spatial scales. Overall, the system is rapidly converting a large baryonic mass into stars over the course of only a few hundred megayears. Our study thus adds new arguments to the growing evidence that submillimeter galaxies are more massive than Lyman break galaxies and more numerous at high redshift than predicted by current semianalytic models of galaxy evolution. Subject headings: galaxies: abundances — galaxies: evolution — galaxies: formation

Dust emission from the lensed Lyman break galaxy cB58

We detect 1.2mm continuum emission from dust in the gravitationally lensed Lyman break galaxy MS 1512+36-cB58. Our detected flux is surprisingly low: relative to local starburst galaxies, cB58 appears to produce somewhat less far-IR emission than its UV reddening predicts. After comparing several different estimates of the sources dust content, we conclude that the apparent discrepancy is most likely related to uncertainty in its UV spectral slope. Alternate scenarios to account for a far-IR deficit which rely on a high dust temperature or differential magnification are less satisfactory. Our result underscores one of the risks inherent in characterizing the cosmic star formation history from rest-UV data alone.

Molecular gas in NUclei of GAlaxies (NUGA) - II. The ringed LINER NGC 7217

S. L. is supported by a Marie Curie Individual Fellowship contract HPMF-CT-20002-01734 from the European Union.

Molecular gas in NUclei of GAlaxies (NUGA) - III. The warped LINER NGC 3718

The research presented in this paper has nbeen financially supported in part by the SFB 494. Stephane Leon is partially supported by DGI Grant AYA 2002-03338 nand Junta de Andalucia.

Millimeter observations of obscured Spitzer 24 μm sources

We present MAMBO 1.2 mm observations of 40 extragalactic sources from the Spitzer First Look Survey that are bright in the mid-IR (S24 μm > 1 mJy) but optically obscured (log > 1). We use these observations to search for cold dust emission, probing the similarity of their spectral energy distributions to star-forming IR galaxies or obscured AGNs. The sample as a whole is well detected at mean S1.2 mm = 0.74 ± 0.09 mJy and S1.2 mm/S24 μm = 0.15 ± 0.03. Seven (three) of the sources are individually detected at >3 σ (>5 σ) levels. Mean millimeter fluxes are higher for sources with the reddest mid-IR/optical colors. Optically faint but with relatively low millimeter-to-mid-IR ratios, the typical SEDs are inconsistent with redshifted SED shapes of local star-forming IR galaxies. They also differ from SEDs of typical submillimeter-selected galaxies, with the 24 μm sources that are individually detected by MAMBO possibly representing intermediate objects. Compared to star-forming galaxies, a stronger but optically obscured mid-IR component without associated strong far-IR emission has to be included. This component may be due to luminous optically obscured AGN, which would represent a significant part of the high-redshift AGN population.

Accounting for the anisoplanatic point spread function in deep wide-field adaptive optics images

In this paper we present the approach we have used to determine and account for the anisoplanatic point spread function (PSF) in deep adaptive optics (AO) images for the Survey of a Wide Area with NACO (SWAN) at the ESO VLT. The survey comprises adaptive optics observations in the Ks band totaling ∼30 arcmin 2 , assembled from 42 discrete fields centered on different bright stars suitable for AO guiding. We develop a parametric model of the PSF variations across the field of view in order to build an accurate model PSF for every galaxy detected in each of the fields. We show that this approach is particularly convenient, as it uses only easily available data and makes no uncertain assumptions about the stability of the isoplanatic angle during any given night. The model was tested using simulated galaxy profiles to check its performance in terms of recovering the correct morphological parameters; we find that the results are reliable up to Ks ∼ 20. 5( KAB ∼ 22.3) in a typical SWAN field. Finally, the model obtained was used to derive the first results from five SWAN fields, and to obtain the AO morphology of 55 galaxies brighter than Ks = 20. These preliminary results demonstrate the unique power of AO observations to derive the details of faint galaxy morphologies and to study galaxy evolution.