arXiv subjects

C. Cesarsky

Publications and source records attributed to C. Cesarsky.

At least 37 records · Page 2Linked to original sources

arXiv2004

ISOCAM observations in the Lockman Hole - II The 14.3 micron deep survey: data reduction, catalogue and source counts

We present a new analysis of the ISOCAM 14.3 micron deep survey in a 20x20 square arcmins area in the Lockman Hole. This survey is intermediate between the ultra-deep surveys and the shallow surveys in the ELAIS fields. The data have been analyzed with the method presented by Lari et al. (2001). We have produced a catalogue of 283 sources detected above the 5-sigma threshold, with fluxes in the interval 0.1-8 mJy. The catalogue is 90% complete at 1 mJy. The positional accuracy, estimated from the cross-correlation of infrared and optical sources, is around 1.5 arcsec. The search for the optical counterparts of the sources in the survey is performed on a medium-deep r' band optical image (5-sigma depth of r'=25), making use of the radio detections when available. The photometry has been checked through simulations and by comparing the data with those presented in a shallower and more extended ISOCAM survey in the Lockman Hole, that we have presented in a companion paper. Only 15% of the 14.3 micron sources do not have an optical counterpart down to r'=25 mag. We use the 6.7/14.3 micron colour as a star/galaxy separator, together with a visual inspection of the optical image and an analysis of the observed Spectral Energy Distribution of the ISOCAM sources. The stars in the sample turn out to be only 6% of the sample. We discuss the 14.3 micron counts of extragalactic sources, combining our catalogue with that obtained from the shallower ISOCAM survey. The data in the two surveys are consistent, and our results fully support the claims in previous works for the existence of an evolving population of infrared galaxies, confirming the evident departure from non-evolutionary model predictions.

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arXiv2004

The Great Observatories Origins Deep Survey - VLT/FORS2 Spectroscopy in the GOODS-South Field

We present the first results of the ESO/GOODS program of spectroscopy of faint galaxies in the Chandra Deep Field South (CDF-S). 399 spectra of 303 unique targets have been obtained in service mode with the FORS2 spectrograph at the ESO/VLT, providing 234 redshift determinations (the median of the redshift distribution is at 1.04). The typical redshift uncertainty is estimated to be sig(z) ~ 0.001. Galaxies have been color selected in a way that the resulting redshift distribution typically spans from z=0.5 to 2. The reduced spectra and the derived redshifts are released to the community through the ESO web page http://www.eso.org/science/goods/ Large scale structure is clearly detected at z ~ 0.67, 0.73, 1.10 and 1.61. Three Lyman-break galaxies have also been included as targets and are confirmed to have redshifts z=4.800, 4.882 and 5.828. In a few cases, we observe clear [OII]3727 rotation curves, even at the relatively low resolution (R = 860) of the present observations. Assuming that the observed velocity structure is due to dynamically-relaxed rotation, this is an indication of large galactic masses (few times 10^(11) solar masses) at z ~ 1.

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arXiv2003

ISOGAL: A deep survey of the obscured inner Milky Way with ISO at 7 and 15 micron and with DENIS in the near-infrared

The ISOGAL project is an infrared survey of specific regions sampling the Galactic Plane selected to provide information on Galactic structure,stellar populations,stellar mass-loss and the recent star formation history of the inner disk and Bulge of the Galaxy. ISOGAL combines 7 and 15 micron ISOCAM observations - with a resolution of 6'' at worst - with DENIS IJKs data to determine the nature of the sources and theinterstellar extinction. We have observed about 16 square degrees with a sensitivity approaching 10-20mJy, detecting ~10^5 sources,mostly AGB stars,red giants and young stars. The main features of the ISOGAL survey and the observations are summarized in this paper,together with a brief discussion of data processing and quality. The primary ISOGAL products are described briefly (a full description is given in Schuller et al. 2003, astro-ph/0304309): viz. the images and theISOGAL-DENIS five-wavelength point source catalogue. The main scientific results already derived or in progress are summarized. These include astrometrically calibrated 7 and 15um images,determining structures of resolved sources; identification and properties of interstellar dark clouds; quantification of the infrared extinction law and source dereddening; analysis of red giant and (especially) AGB stellar populations in the central Bulge,determining luminosity,presence of circumstellar dust and mass--loss rate,and source classification,supplemented in some cases by ISO/CVF spectroscopy; detection of young stellar objects of diverse types,especially in the inner Bulge with information about the present and recent star formation rate; identification of foreground sources with mid-IR excess. These results are the subject of about 25 refereed papers published or in preparation.

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arXiv2002

An unusual iron Lo-BAL quasar detected by ISOCAM

We report the discovery of an unusual low--ionization broad absorption line quasar at z=1.776 which exhibits absorption lines from many excited states of Feii. This member of the rare class of 'FeLoBAL' quasars was serendipitously found in a mid-infrared (MIR) survey of distant clusters carried out with the ISOCAM camera. ISO J005645.1-273816 has a high MIR to UV luminosity ratio, suggesting a strong dust obscuration plus emission from very hot dust. This characteristic makes MIR surveys particularly efficient at detecting LoBAL quasars.

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arXiv2002

ESO for GOODS' sake

Currently public ESO data sets pertinent to the CDFS/GOODS field are briefly illustrated along with an indication on how to get access to them. Future ESO plans for complementing the GOODS database with optical/IR imaging and optical spectroscopy are also described.

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arXiv2002

The Bulk of the Cosmic Infrared Background Resolved by ISOCAM

We have computed the 15 microns integrated galaxy light produced by ISOCAM galaxies above a sensitivity limit of 50 microJy. It sets a lower limit to the 15 microns extragalactic background light of (2.4+/-0.5) nW/m^2/Hz. The redshift distribution of the ISOCAM galaxies is inferred from the spectroscopically complete sample of galaxies in the Hubble Deep Field North (HDFN). We demonstrate that mid (MIR) and far (FIR) infrared luminosities correlate for local star forming galaxies and that this correlation is consistent with the radio-FIR one up to z ~ 1. From these correlations, about 75 % of the ISOCAM galaxies are found to belong to the class of luminous infrared galaxies (L[IR] >= 10^11 Lsol), with star formation rates of the order of ~ 100 Msol/yr. The cross-correlation with the deepest X-ray surveys from the Chandra and XMM-Newton observatories in the HDFN and Lockman Hole respectively, indicates that at most 20 % of the 15 microns integrated galaxy light is due to active galactic nuclei (AGNs) unless a large population of AGNs was missed by Chandra and XMM-Newton. The contribution of ISOCAM galaxies to the peak of the cosmic infrared background (CIRB) at 140 microns was computed from the MIR-FIR correlations for star forming galaxies and from the spectral energy distribution of the Seyfert 2, NGC 1068, for AGNs. We find that the galaxies unveiled by ISOCAM surveys are responsible for the bulk of the CIRB, i.e (16+/-5) nW/m^2/Hz as compared to the (25+/-7) nW/m^2/Hz measured with the COBE satellite, with less than 10 % due to AGNs. Since the CIRB contains most of the light radiated over the history of star formation in the universe, this means that a large fraction of present-day stars must have formed during a dusty starburst event similar to those revealed by ISOCAM.

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arXiv2001

Hidden star-formation in the cluster of galaxies Abell 1689

At a redshift of 0.18, Abell 1689 is so far the most distant cluster of galaxies for which substantial mid-infrared (MIR) data have been published. We present here the follow-up optical photometric and spectroscopic observations which were used to study the individual properties of the galaxies members of A1689. Sources with a low [15 micron] / [6.75 micron] flux ratio typically consist of luminous passive early-type galaxies while those with a high MIR color index are mainly luminous, blue, emission-line, morphologically disturbed spirals, i.e. the star-forming galaxies usually associated with the 'Butcher-Oemler' effect. On the other hand, at least 30% of the 15 micron sources have optical counterparts showing no evidence of current star-formation activity, while their 15 micron emission is most likely due to obscured star formation. We argue that the LW3 luminosity measured in the cluster members is a reliable tracer of the total infrared luminosity, L(IR). We derive from L(IR) a star-formation rate free of dust extinction, SFR(IR), which we compare with that determined in the optical from the flux of the [OII] emission line, SFR(opt). The highest total star formation rates (11 Msun/yr) and dust extinction are measured in those galaxies exhibiting in their optical spectrum a signature of a dusty starburst. In contrast, none of the galaxies with post-starburst optical spectra has been detected by ISOCAM. We find a median SFR(IR) of the LW3-detected galaxies of 2 Msun/yr, that is ten times higher than the median SFR(opt) of the [OII] detected galaxies. The ratio SFR(IR)/SFR(opt) is in fact very high, ranging between 10 and 100 for LW3-detected galaxies with [OII] emission. We conclude that a major part, at least 90%, of the star formation activity taking place in Abell 1689 is hidden.

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arXiv2001

The first ISO ERO: a dusty quasar at z = 1.5

We report the discovery of an extremely red object (ERO) in a medium-deep ISOCAM extragalactic survey. The object is also a radio source. Subsequent VLT NIR spectroscopy revealed a prominent Halpha line giving a redshift of 1.5. We present the spectrum and photometric data points and discuss evidence that ISO J1324-2016 is a quasar harbouring a significant amount of very hot dust.

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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

Mass-Losing Semiregular Variable Stars in Baade's Windows

By cross-correlating the results of two recent large-scale surveys, the general properties of a well defined sample of semi-regular variable stars have been determined. ISOGAL mid-infrared photometry and MACHO lightcurves are assembled for approximately 300 stars in the Baade's Windows of low extinction towards the Galactic bulge. These stars are mainly giants of late M spectral type, evolving along the asymptotic giant branch (AGB). They are found to possess a wide and continuous distribution of pulsation periods and to obey an approximate log~period -- bolometric magnitude relation or set of such relations. Approximate mass-loss rates in the range of 1e-8 to 5e-7 M_sun per year are derived from ISOGAL mid-infrared photometry and models of stellar spectra adjusted for the presence of optically-thin circumstellar silicate dust. Mass-loss rates depend on luminosity and pulsation period. Some stars lose mass as rapidly as short-period Miras but do not show Mira-like amplitudes. A period of 70 days or longer is a necessary but not a sufficient condition for mass loss to occur. For AGB stars in the mass-loss ranges that we observe, the functional dependence of mass-loss rate on temperature and luminosity is found to be in agreement with recent theoretical predictions. If we include our mass-loss rates with a sample of extreme mass-losing AGB stars in the Large Magellanic Cloud, we get the general result for AGB stars that mass-loss rate is proportional to luminosity^{2.7}, valid for AGB stars with 10^{-8} to 10^{-4} M_sun per year (Abridged).

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arXiv2001

Mid-infrared observations of NGC 1068 with ISOCAM

We report on Mid-Infrared (MIR) observations of the Seyfert 2 galaxy NGC 1068, obtained with ISOCAM in low-resolution spectro-imaging mode. The spatial resolution (around 5 arcsec) allows us to disentangle the circumnuclear starburst regions from the emission of the active galactic nucleus (AGN). The global spatial distribution of the Unidentified Infrared Bands (UIBs) is similar to the cold dust component, traced by the 450 microns emission and the gaseous component obtained from the CO(1-0) map. However, a shift between the maximum of the UIB and 450 microns emission is clearly seen in our maps. The UIBs in the MIR (5-16 microns) originate almost exclusively from the starburst regions in the galactic disk with an emission peaking at the extremity of the stellar/ gaseous bar at a distance of 1 kpc from the AGN. The spectrum of the nucleus is characterized over the whole 5-16 microns range by a strong continuum which can be fitted with a power law of index -1.7. Moreover, the high [NeIII]/[NeII] ratio (>2.5) in the nuclear region argues for a hard radiation field from the AGN. Observations indicate that the AGN in NGC 1068 contributes less than 5% to the total integrated UIB emission even though its hot dust continuum contributes as much as 75% to the total MIR flux. On the contrary, the nuclear contribution to the cold dust emission decreases considerably at submillimeter wavelengths and does not represent more than 25% of the total integrated emission at 450 microns.

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arXiv2000

Mid-infrared imaging and spectrophotometry of N 66 in the SMC with ISOCAM

We present observations with the mid-infrared camera ISOCAM on board ISO of the major star-forming region N66 in the Small Magellanic Cloud and of its surroundings. These observations were performed with broad filters and the CVF giving a spectral resolution of about 40. In addition, CO(2-1) data are presented, allowing us to identify and study how hot dust relates with the different phases of the Interstellar Medium present in N66. The spectra are dominated by the strong emission of fine structure line. Monochromatic maps have been made in the [NeIII] 15.6 microns and [SIV] 10.5 microns line. There are significant differences between their distributions, due to the effects of density and of shocks. Aromatic Infrared Bands are seen at various places in the field but they are generally faint. They exhibit a variety of shapes and relative intensities, suggesting that a diversity of carbonaceous materials are present. Silicate emission is also clearly visible in the central condensation and in a few others and emission from hot small grains longward of 10 microns is present in the whole region. All these dust components are heated by the very strong far UV radiation of the many young, massive stars contained in the region. The interstellar radiation field (ISRF) at 1600 A is >= 10^5 times the ISRF of the solar neighborhood in the peaks of MIR emission. The relative contributions of the dust components to the MIR spectra seem to depend on the intensity and the hardness of the far UV field. In general the 15/6.75 microns intensity ratio is higher than in relatively quiescent galactic regions but it is not as high as expected for a linear increase with ISRF. We interpret this behavior as due to the destruction of both AIBs carriers and VSGs in a very high ISRF.

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arXiv2000

Mid-infrared diagnostics to distinguish AGNs from starbursts

We present new mid-infrared (MIR) diagnostics to distinguish emission of active galactic nuclei (AGN) from that originating in starburst regions. Our method uses empirical spectroscopic criteria based on the fact that MIR emission from star forming or active galaxies arises mostly from HII regions, photo-dissociation regions (PDRs) and AGNs. The analysis of the strength of the 6.2micron Unidentified Infrared Band (UIB) and the MIR continuum shows that UIBs are very faint or absent in regions harboring the intense and hard radiation fields of AGNs and pure HII regions, where the UIB carriers could be destroyed. The MIR signature of AGNs is the presence of an important continuum in the 3-10micron band which originates from very hot dust heated by the intense AGN radiation field. Using these two distinct spectral properties found in our MIR templates, we build diagnostic diagrams which provide quantitative estimates of the AGN, PDR and HII region contribution in a given MIR spectrum. This new MIR classification can be used to reveal the presence of AGNs highly obscured by large columns of dust.

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arXiv2000

Spatial resolution bias in the mid-infrared Starburst/AGN classification

We present the effects of limited spatial resolution to the observed mid-infrared (MIR) spectrum of an active galactic nucleus (AGN) surrounded by a disk with massive star forming regions. Using MIR observations of the face-on nearby Seyfert 1 galaxy NGC 6814, we vary the observing aperture and examine the evolution of the observed AGN/starburst fraction with our MIR diagnostic. We show that the spatial resolution of ISOCAM is sufficient to disentangle AGN from starburst features in nuclear regions of nearby galaxies (D<50Mpc). However, with the exception of a few ultra-luminous galaxies, dilution effects hide completely the AGN contribution in more distant galaxies.

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arXiv2000

The European Large Area ISO Survey II: mid-infrared extragalactic source counts

We present preliminary source counts at 6.7um and 15um from the Preliminary Analysis of the European Large Area ISO survey, with limiting flux densities of \~2mJy at 15um & ~1mJy at 6.7um. We separate the stellar contribution from the extragalactic using identifications with APM sources made with the likelihood ratio technique. We quantify the completeness & reliability of our source extraction using (a) repeated observations over small areas, (b) cross-IDs with stars of known spectral type, (c) detections of the PSF wings around bright sources, (d) comparison with independent algorithms. Flux calibration at 15um was performed using stellar IDs; the calibration does not agree with the pre-flight estimates, probably due to effects of detector hysteresis and photometric aperture correction. The 6.7um extragalactic counts are broadly reproduced in the Pearson & Rowan-Robinson model, but the Franceschini et al. (1997) model underpredicts the observed source density by ~0.5-1 dex, though the photometry at 6.7um is still preliminary. At 15um the extragalactic counts are in excellent agreement with the predictions of the Pearson & Rowan-Robinson (1996), Franceschini et al. (1994), Guiderdoni et al. (1997) and the evolving models of Xu et al. (1998), over 7 orders of magnitude in 15um flux density. The counts agree with other estimates from the ISOCAM instrument at overlapping flux densities (Elbaz et al. 1999), provided a consistent flux calibration is used. Luminosity evolution at a rate of (1+z)^3, incorporating mid-IR spectral features, provides a better fit to the 15um differential counts than (1+z)^4 density evolution. No-evolution models are excluded, and implying that below around 10mJy at 15um the source counts become dominated by an evolving cosmological population of dust-shrouded starbursts and/or active galaxies.

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arXiv2000

NIR Spectroscopy with the VLT of a sample of ISO selected Hubble Deep Field South Galaxies

A new population of faint galaxies characterized by an extremely high rate of evolution with redshift up to z~1.5 has recently been discovered by ISO. These sources are likely to contribute significantly to the cosmic far-IR extragalactic background. We have carried out near-infrared VLT-ISAAC spectroscopy of a sample of ISOCAM galaxies from the Hubble Deep Field South. The rest-frame R-band spectral properties of the ISO population resembles that of powerful dust-enshrouded active starburst galaxies.

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arXiv1999

The European Large Area ISO Survey: ELAIS

The European Large Area ISO Survey (ELAIS) has surveyed 12 square degrees of the sky at 15 and 90 microns, and subsets of this area at 6.75 and 175 microns, using the Infrared Space Observatory (ISO). This project was the largest single open time programme executed by ISO, taking 375 hours of data. A preliminary catalogue of more than 1000 galaxies has been produced. In this talk we describe the goals of the project, describe the follow-up programmes that are in progress, and present some first scientific results including a provisional number count analysis at 15 and 90 microns.

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arXiv1999

FIRBACK Far Infrared Survey with ISO: Data Reduction, Analysis and First Results

FIRBACK is one of the deepest cosmological surveys performed in the far infrared, using ISOPHOT. We describe this survey, its data reduction and analysis. We present the maps of fields at 175 microns. We point out some first results: source identifications with radio and mid infrared, and source counts at 175 microns. These two results suggest that half of the FIRBACK sources are probably at redshifts greater than 1. We also present briefly the large follow-up program.

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