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M. Rowan-Robinson

Publications and source records attributed to M. Rowan-Robinson.

At least 145 records · Page 8Linked to original sources
arXiv2001

Ultraluminous Infrared Galaxies: Atlas of Near-Infrared Images

A sample of 27 ultraluminous infrared galaxy (ULIRG) systems has been imaged at 1.6 microns using the HST Near Infrared Camera and Multi-Object Spectrometer (NICMOS). These ULIRGs are from a larger sample also imaged with HST in the I-band. Images and catalog information for the NICMOS subsample, as well as brief morphological descriptions of each system are presented. Inspection of the infrared images and a comparison with optical images of these systems shows that at least 85% are obviously composed of two or more galaxies involved in a close interaction or merger event, with as many as 93% showing some signs of interaction history. Approximately 37% of the systems show either spectroscopic or morphological characteristics of an active galactic nucleus (AGN). The infrared morphologies of these systems are generally less complicated or disturbed than their optical morphologies, indicating that some of the small-scale features seen in optical images are likely due to complicated patterns of dust obscuration, as well as widely distributed star formation activity. In some systems the high-resolution HST infrared images have revealed nuclear remnants that are obscured or unidentified in ground-based imaging, which has led to changes in previously determined interaction stage classifications or system content. In general, however, the NICMOS images support previous conclusions from previous HST optical imaging.

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arXiv2001

The extended counterpart of submm source Lockman850.1

The IRAM Plateau de Bure mm interferometer and deep K-band imaging have been used to identify the brightest submm source detected in the Lockman field of the UK 8mJy SCUBA survey. The near infrared counterpart is an extended (20-30kpc), clumpy, and extremely red object. The spectral energy distribution suggests it to be a dusty star forming object at a redshift of about 3 (2-4). Its star formation rate and near-infrared properties are consistent with Lockman850.1 being a massive elliptical in formation.

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arXiv2001

The European Large Area ISO Survey VI - Discovery of a new hyperluminous infrared galaxy

We report the discovery of the first hyperluminous infrared galaxy (HyLIG) in the course of the European Large Area ISO Survey (ELAIS). This object has been detected by ISO at 6.7, 15, and 90 microns, and is found to be a broad-line, radio-quiet quasar at a redshift: z = 1.099. From a detailed multi-component model fit of the spectral energy distribution, we derive a total infrared luminosity: L_IR (1-1000 microns) ~ 1.0 x 10E13 h_65^-2 L_sun (q_0 = 0.5), and discuss the possible existence of a starburst contributing to the far-IR output. Observations to date present no evidence for lens magnification. This galaxy is one of the very few HyLIGs with an X-ray detection. On the basis of its soft X-ray properties, we suggest that this broad-line object may be the face-on analogue of narrow-line, Seyfert-like HyLIGs.

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arXiv2001

HST/WFPC2 Imaging of the QDOT Ultraluminous Infrared Galaxy Sample

We present HST WFPC2 V band imaging for 23 Ultraluminous Infrared Galaxies taken from the QDOT redshift survey. The fraction of sources observed to be interacting is 87%. Most of the merging systems show a number of compact `knots', whose colour and brightness differ substantially from their immediate surroundings. Colour maps for nine of the objects show a non-uniform colour structure. Features include blue regions located towards the centres of merging systems which are likely to be areas of enhanced star formation, and compact red regions which are likely to be dust shrouded starbursts or AGN. The host galaxies of the QSOs in the sample were found to be either interacting systems or ellipticals. Our data shows no evidence that ULIRGs are a simple transition stage between galaxy mergers and QSOs. We propose an alternative model for ULIRGs based on the morphologies in our sample and previous N-body simulations. Under this model ULIRGs as a class are much more diverse than a simple transition between galaxy merger and QSO. The evolution of IR power source and merger morphology in ULIRGs is driven solely by the local environment and the morphologies of the merger progenitors.

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arXiv2001

The ELAIS Deep X-ray Survey

We present initial follow-up results of the ELAIS Deep X-ray Survey which is being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray sources are detected in our two 75 ks ACIS-I observations in the well-studied ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to R=26 with a median magnitude of R=24. We show that objects which are unresolved optically (i.e. quasars) follow a correlation between their optical and X-ray fluxes, whereas galaxies do not. We also find that the quasars with fainter optical counterparts have harder X-ray spectra, consistent with absorption at both wavebands. Initial spectroscopic follow-up has revealed a large fraction of high-luminosity Type 2 quasars. The prospects for studying the evolution of the host galaxies of X-ray selected Type 2 AGN are considered.

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arXiv2001

FIRBACK: III. Catalog, Source counts, and cosmological implications of the 170 micron ISO Deep survey

The FIRBACK (Far Infrared BACKground) survey is one of the deepest imaging surveys carried out at 170 microns with ISOPHOT onboard ISO, and is aimed at the study of the structure of the Cosmic Far Infrared Background. This paper provides the analysis of resolved sources. After a validated process of data reduction and calibration, we perform intensive simulations to optimize the source extraction, measure the confusion noise (sigma_c = 45 mJy), and give the photometric and astrometric accuracies. 196 galaxies with flux S > 3 sigma_c are detected in the area of 3.89 square degrees. Counts of sources with flux S > 4 sigma_c present a steep slope of 3.3 +/- 0.6 on a differential "logN-logS" plot between 180 and 500 mJy. As a consequence, the confusion level is high and will impact dramatically on future IR deep surveys. This strong evolution, compared with a slope of 2.5 from Euclidian geometry, is in line with models implying a strongly evolving Luminous Infrared Galaxy population. The resolved sources account for less than 10% of the Cosmic Infrared Background at 170 microns, which is expected to be resolved into sources in the 1 to 10 mJy range.

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arXiv2001

A New Method for ISOCAM Data Reduction - I. Application to the European Large Area ISO Survey Southern Field: Method and Results

We have developed a new data reduction technique for ISOCAM LW data and have applied it to the European Large Area ISO Survey (ELAIS) LW3 (15 micron) observations in the southern hemisphere (S1). This method, known as LARI technique and based on the assumption of the existence of two different time scales in ISOCAM transients (accounting either for fast or slow detector response), was particularly designed for the detection of faint sources. In the ELAIS S1 field we obtained a catalogue of 462 15 micron sources with signal-to-noise ratio >= 5 and flux densities in the range 0.45 - 150 mJy (filling the whole flux range between the Deep ISOCAM Surveys and the IRAS Faint Source Survey). The completeness at different flux levels and the photometric accuracy of this catalogue have been tested with simulations. Here we present a detailed description of the method and discuss the results obtained by its application to the S1 LW3 data.

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arXiv2001

The European Large Area ISO Survey V: a BeppoSAX hard X-ray survey of the S1 region

We present BeppoSAX observations of the Southern S1 region in the European Large Area ISO Survey (ELAIS). These observations cover an area of ~1.7 sq. deg. and reach an on-axis (~0.7 sq. deg) 2-10 keV (HX) sensitivity of ~10E-13 cgs. This is the first HX analysis of an ISOCAM survey. We detect 9 sources with a signal to noise ratio SNR_HX>3, 4 additional sources with a 1.3 to 10 keV (T) SNR_T>3 and 2 additional sources which appear to be associated with QSOs with SNR_T>2.9. The number densities of the SNR_HX>3 sources are consistent with the ASCA and BeppoSAX logN-logS functions. Six BeppoSAX sources have reliable ISOCAM 15 micron counterparts within ~60 arcsec. All these ISOCAM sources have optical counterparts of R<20 mags. Five of these sources have been previously optically classified giving 4 QSOs and 1 BALQSO at z=2.2. The remaining unclassified source has X-ray and photometric properties consistent with that of a nearby Seyfert galaxy. One further HX source has a 2.6sigma ISOCAM counterpart associated with a galaxy at z=0.325. If this ISOCAM source is real, the HX/MIR properties suggest either an unusual QSO or a cD cluster galaxy. We have constructed MIR and HX spectral energy distributions to compute the expected HX/MIR ratios for these classes of objects up to z=3.2 and assess the HX/MIR survey depth. The BALQSO has an observed X-ray softness ratio and HX/MIR flux ratio similar to QSOs but different to those found for low redshift BALQSOs. This difference can be explained in terms of absorption, and suggests that high redshift BALQSOs should be comparatively easy to detect in the HX band, allowing their true fraction in the high redshift QSO population to be determined (ABRIDGED).

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arXiv2000

Predicting the peculiar velocities of nearby PSC-z galaxies using the Least Action Principle

We use the Least Action Principle to predict the peculiar velocities of PSC-z galaxies inside $cz=2000$\km. Linear theory is used to account for tidal effects to $cz=15000$\km, and we iterate galaxy positions to account for redshift distortions. As the Least Action Principle is valid beyond Linear theory, we can predict reliable peculiar velocities even for very nearby galaxies (ie $cz \leq 500$\km). These predicted peculiar velocities are then compared with the observed velocities of 12 galaxies with Cepheid distances. The combination of the PSC-z galaxy survey (with its large sky coverage and uniform selection), with the accurate Cepheid distances, makes this comparison relatively free from systematic effects. We find that galaxies are good tracers of the mass, even at small ($\leq 10$\mpc) scales; and under the assumption of no biasing, $0.25 \leq β\leq 0.75$ (at 90% confidence). We use the reliable predicted peculiar velocities to estimate the Hubble constant \ho from the local volume without ``stepping up'' the distance ladder, finding a confidence range of 65-75\kmM (at 90% confidence).

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arXiv2000

The star-formation history of the universe - an infrared perspective

A simple and versatile parameterized approach to the star formation history allows a quantitative investigation of the constraints from far infrared and submillimetre counts and background intensity measurements. The models include four spectral components: infrared cirrus (emission from interstellar dust), an M82-like starburst, an Arp220-like starburst and an AGN dust torus. The 60 $μ$m luminosity function is determined for each chosen rate of evolution using the PSCz redshift data for 15000 galaxies. The proportions of each spectral type as a function of 60 $μ$m luminosity are chosen for consistency with IRAS and SCUBA colour-luminosity relations, and with the fraction of AGN as a function of luminosity found in 12 $μ$m samples. The luminosity function for each component at any wavelength can then be calculated from the assumed spectral energy distributions. With assumptions about the optical seds corresponding to each component and, for the AGN component, the optical and near infrared counts can be accurately modelled. A good fit to the observed counts at 0.44, 2.2, 15, 60, 90, 175 and 850 $μ$m can be found with pure luminosity evolution in all 3 cosmological models investigated: $Ω_o$ = 1, $Ω_o$ = 0.3 ($Λ$ = 0), and $Ω_o$ = 0.3, $Λ$ = 0.7. All 3 models also give an acceptable fit to the integrated background spectrum. Selected predictions of the models, for example redshift distributions for each component at selected wavelengths and fluxes, are shown. The total mass-density of stars generated is consistent with that observed, in all 3 cosmological models.

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arXiv2000

Models for infrared and submillimetre counts and backgrounds

A simple and versatile parameterized approach to the star formation history allows a quantitative investigation of the constraints from far infrared and submillimetre counts and background intensity measurements. The models include four spectral components: infrared cirrus, an M82-like starburst, an Arp220-like starburst and an AGN dust torus. The 60 $μ$m luminosity function is determined for each chosen rate of evolution using the PSCz redshift data for 15000 galaxies. The proportions of each spectral type as a function of 60 $μ$m luminosity are chosen for consistency with IRAS and SCUBA colour-luminosity relations, and with the fraction of AGN as a function of luminosity found in 12 $μ$m samples. A good fit to the observed counts at 0.44, 2.2, 15, 60, 90, 175 and 850 $μ$m can be found with pure luminosity evolution in all 3 cosmological models investigated: $Ω_o$ = 1, $Ω_o$ = 0.3 ($Λ$ = 0), and $Ω_o$ = 0.3, $Λ$ = 0.7. All 3 models also give an acceptable fit to the integrated background spectrum. The total mass-density of stars generated is consistent with that observed, in all 3 cosmological models.

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arXiv2000

Cosmological Parameters: do we already know the final answer ?

Some of the arguments which support the strong concensus for an $Ω_o$ = 0.3, $λ_o$ = 0.7 model are reexamined. Corrections for Malmquist bias, local flow and metallicity suggest a revised value for $H_o$ of 63 $\pm$ 6 km/s/Mpc, improving the age problems for an $Ω_o$ = 1 universe. The latest CMB results may require a high baryon density and hence new physics, for example a strong lepton asymmetry. Difficulties for the $Ω_o$ = 1 model with cluster evolution, the baryon content of clusters, and the evidence from Type Ia supernovae favouring low $Ω_o$, $Λ> 0$ models, are discussed critically.

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arXiv2000

Starburst activity in a ROSAT Narrow Emission-Line Galaxy

We present multiwaveband photometric and optical spectropolarimetric observations of the R=15.9 narrow emission line galaxy R117_A which lies on the edge of the error circle of the ROSAT X-ray source R117 (from McHardy et al 1998). The overall spectral energy distribution of the galaxy is well modelled by a combination of a normal spiral galaxy and a moderate-strength burst of star formation. The far infra-red and radio emission is extended along the major axis of the galaxy, indicating an extended starburst. On positional grounds, the galaxy is a good candidate for the identification of R117 and the observed X-ray flux is very close to what would be expected from a starburst of the observed far infra-red and radio fluxes. Although an obscured high redshift QSO cannot be entirely ruled out as contributing some fraction of the X-ray flux, we find no candidates to K=20.8 within the X-ray errorbox and so conclude that R117_A is responsible for a large fraction, if not all, of the X-ray emission from R117. Searches for indicators of an obscured AGN in R117_A have so far proven negative; deep spectropolarimetric observations show no signs of broad lines to a limit of one per cent and, for the observed far infra-red and radio emission, we would expect a ten times greater X-ray flux if the overall emission were powered by an AGN. We therefore conclude that the X-ray emission from R117 is dominated by starburst emission from the galaxy R117_A.

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arXiv2000

The European Large Area ISO Survey IV: the preliminary 90 micron luminosity function

We present the luminosity function of 90um selected galaxies from the European Large Area ISO Survey (ELAIS), extending to z=0.3. Their luminosities are in the range 10^9 < h_65^-2 L/Lsun < 10^12, i.e. non-ultraluminous. From our sample of 37 reliably detected galaxies in the ELAIS S1 region from the Efstathiou et al. (2000) S_90 >= 100mJy database, we found optical, 15um or 1.4GHz identifications for 24 (65%). We have obtained 2dF and UK Schmidt FLAIR spectroscopy of 89% of IDs to rigid multivariate flux limits. We construct a luminosity function assuming (a) our spectroscopic subset is an unbiased sparse sample, and (b) there are no galaxies which would not be represented in our spectroscopic sample at {\it any} redshift. We argue that we can be confident of both assumptions. We find the luminosity function is well-described by the local 100um luminosity function of Rowan-Robinson, Helou & Walker (1987). {\it Assuming} this local normalisation, we derive luminosity evolution of (1+z)^{2.45\pm0.85} (95% confidence). We argue that star formation dominates the bolometric luminosities of these galaxies and we derive comoving star formation rates in broad agreement with the Flores et al. (1999) and Rowan-Robinson et al. (1997) mid-IR-based estimates.

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arXiv2000

The European Large Area ISO Survey III: 90micron extragalactic source counts

We present results and source counts at 90micron extracted from the Preliminary Analysis of the European Large Area ISO Survey (ELAIS). The survey covered about 11.6 square degrees of the sky in four main areas and was carried out with the PHOT instrument onboard the Infrared Space Observatory (ISO). The survey is at least an order of magnitude deeper than the IRAS 100micron survey and is expected to provide constraints on the formation and evolution of galaxies. The majority of the detected sources are associated with galaxies on optical images. In some cases the optical associations are interacting pairs or small groups of galaxies suggesting the sample may include a significant fraction of luminous infrared galaxies. The source counts extracted from a reliable subset of the detected sources are in agreement with strongly evolving models of the starburst galaxy population.

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arXiv2000

PSCz Superclusters: Detection, Shapes & Cosmological Implications

We study the possibility of correctly identifying superclusters, from the smooth galaxy density field of the PSCz redshift catalogue, and of recovering their true shapes in the presence of a bias introduced by the coupling between the selection function and the constant radius smoothing. Using simulations we quantify such systematic biases in the smoothed PSCz density field and after applying the necessary corrections we study the PSCz supercluster multiplicity and morphologies using a differential geometry definition of shape. Our results strongly suggest that filamentariness is the dominant morphological feature of PSCz superclusters. Finally, we compare our results with those expected in three different cosmological models and find that the LCDM model performs better than Omega_m=1 CDM models.

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arXiv2000

Starburst galaxies and structure in the submillimetre background towards the Hubble Deep Field

We use an 850-micron SCUBA map of the HDF to study the dust properties of optically-selected starburst galaxies at high redshift. Although the 850-micron map does not allow detection of the majority of individual sources, we show that the galaxies with the highest UV star-formation rates are detected statistically, with a flux density of about S_{850}=0.2 mJy for an apparent UV star-formation rate of 1 h^{-2} msun yr^{-1}. This level of submillimetre output indicates that the total star-forming activity is on average a factor of approximately 6 times larger than the rate inferred from the UV output of these galaxies. The general population of optical starbursts is then predicted to contribute at least 25 per cent of the 850-micron background. We carry out a power-spectrum analysis of the map, which yields some evidence for angular clustering of the background source population, but at a level lower than that seen in Lyman-break galaxies. Together with other lines of argument, particularly from the NICMOS HDF data, this suggests that the 850-micron background originates over an extremely wide range of redshifts -- perhaps 1 < z < 6.

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