Bruno Altieri | Space Science Faculty of ESA (original) (raw)

Papers by Bruno Altieri

We present low resolution spectrophotometric and imaging ISO observations of a sample of 54 AGN's... more We present low resolution spectrophotometric and imaging ISO observations of a sample of 54 AGN's over the 2.5-11 micron range. The observations generally support unification schemes and set new constraints on models of the molecular torus.

Iso Beyond the Peaks the 2nd Iso Workshop on Analytical Spectroscopy, Oct 30, 2000

Astronomy and Astrophysics, Apr 21, 2000

We present low resolution spectrophotometric and imaging ISO observations of a sample of 57 AGNs ... more We present low resolution spectrophotometric and imaging ISO observations of a sample of 57 AGNs and one non-active SB galaxy over the 2.5-11 mu m range. The sample is about equally divided into type I (<= 1.5; 28 sources) and type II (> 1.5; 29 sources) objects. The mid-IR (MIR) spectra of type I (Sf1) and type II (Sf2) objects are statistically different: Sf1 spectra are characterized by a strong continuum well approximated by a power-law of average index < alpha > = -0.84+/-0.24 with only weak emission features from Polycyclic Aromatic Hydrocarbon (PAH) bands at 3.3, 6.2, 7.7 and 8.6 mu m. In sharp contrast to Sf1s, most Sf2s display a weak continuum but very strong PAH emission bands, with equivalent widths (EW) up to 7.2 mu m. On the other hand, Sf1s and Sf2s do not have statistically different PAH luminosities while the 7 mu m continuum is on the average a factor ~ 8 less luminous in Sf2s than in Sf1s. Because the PAH emission is unrelated to the nuclear activity and arises in the interstellar medium of the underlying galactic bulge, its EW is a sensitive nuclear redenning indicator. These results are consistent with unification schemes and imply that the MIR nuclear continuum source of Sf2s is, on the average, extinguished by 92+/-37 visual magnitudes whereas it is directly visible in Sf1s. The dispersion in Sf2's PAH EW is consistent with the expected spread in viewing angles. Those Sf2s with EW(PAH) > 5 μm suffer from an extinction Av > 125 magnitudes and are invariably extremely weak X-ray sources. Such Sf2s presumably represent the highly inclined objects where our line of sight intercepts the full extent of the molecular torus. Conversely, about a third of the Sf2s have PAH EW <= 2 mu m, in the range of Sf1s. Among them, those which have been observed in spectropolarimetry and/or in IR spectroscopy invariably display ``hidden'' broad lines. As proposed by Heisler et al. (\cite{heisler}), such Sf2s are most likely seen at grazing incidence such that one has a direct view of both the ``reflecting screen'' and the torus inner wall responsible for the near and mid-IR continuum. Our observations therefore constrain the screen and the torus inner wall to be spatially co-located. Finally, the 9.7 mu m Silicate feature appears weakly in emission in Sf1s, implying that the torus vertical optical thickness cannot significantly exceed 1024 cm-2. Based on observations with ISO, an ESA projects with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Tables 2, 3, 4, 5 are only available in electronic form via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

We discuss the photometric calibration of ISOPHOT for point sources in the wavelength range from ... more We discuss the photometric calibration of ISOPHOT for point sources in the wavelength range from 3.2 to 240 μm for the aperture photometer (PHT-P) and the FIR camera section (PHT-C). To correct for temporal drifts of detector responsivities, all observations included reference measurements against stable internal sources. These have been absolutely calibrated in-orbit against well known celestial standards. In this process corrections were derived for instrumental effects like nonlinearities, signal-transients, time variable dark current or misalignments. For staring- or raster-observations of point sources in standard configurations, the scatter of the individual data points around the derived calibration relations is a measure of the consistency and typical accuracy of the calibration.

EAS Publications Series, 2008

ABSTRACT

ESA&amp;amp;#39;s Infrared Space Observatory (ISO) was used to perform a deep survey with... more ESA&amp;amp;#39;s Infrared Space Observatory (ISO) was used to perform a deep survey with ISOCAM through three massive gravitationally lensing clusters of galaxies. The total area surveyed depends on source flux, with nearly seventy square arcminutes covered for the brighter flux levels in maps centred on the three clusters Abell 370, Abell 2218 and Abell 2390. We present maps and photometry

We observed both Mars and Deimos with the ESA Infrared Space Observatory (ISO) during July and Au... more We observed both Mars and Deimos with the ESA Infrared Space Observatory (ISO) during July and August 1997. Our observations were conducted using the infrared camera (CAM) and the short-wave spectrometer (SWS) instruments. The apparent angular diameter of the planet was small during this time (6.8'' to 5.8\arcsec) and the phase angle was large ( ~ 40(deg) ), but this was the only time that ISO could observe Mars within the telescope's rather stringent pointing constraints. CAM observations of Mars were conducted in the CAM04 CVF observing mode on 29 July and 12, 18, and 27 August 1997 UT. Each observation was separated by ~ 90(deg) of Mars central meridian longitude in order to sample the entire surface. Images were obtained at 130 wavelengths between 2.7 and 5.1 \micron\ through CAM's CVF filter (lambda /Delta lambda ~ 40). The spatial resolution of the images is quite poor ( ~ 1500 km/pixel) because of the 1.5'' IFOV of CAM pixels. The resolution is adequat...

ABSTRACT At which cosmic epoch did massive galaxy clusters assemble their baryons? How does star ... more ABSTRACT At which cosmic epoch did massive galaxy clusters assemble their baryons? How does star formation occur in the most massive, most rapidly collapsing dark-matter-dense environments in the early Universe? To answer these questions, we take the completely novel approach to select the most extreme z>~2 star-forming overdensities seen over the entire sky. This selection nicely complements the other existing selections for high redshift clusters (i.e., by stellar mass, or by total mass like Sunyaev-Zeldovish (SZ) or X-ray selection). We make use of the Planck all-sky submillimetre survey to systematically identify the rarest, most luminous high-redshift sub-mm sources on the sky, either strongly gravitationally lensed galaxies, or the joint FIR/sub-mm emission from multiple intense starbursts. We observed 228 Planck sources with Herschel/SPIRE and discovered that most of them are overdensities of red galaxies with extremely high star formation rates (typically 7.e3 Msun/yr for a structure). Only Spitzer data can allow a better understanding of these promising Planck+Herschel selected sources, as is shown on a first set of IRAC data on 40 targets in GO9: (i) the good angular resolution and sensitivity of IRAC allows a proper determination of the clustered nature of each Herschel/SPIRE source; (ii) IRAC photometry (often associated with J, K) allows a good estimate of the colors and approximate photometric redshift. Note spectroscopic redshifts are available for two cluster candidates, at z=1.7 and z=2.3, confirming their high redshift nature. The successful GO9 observation of 40 fields showed that about half to be >7sigma overdensities of red IRAC sources. These observations were targeting the whole range of Herschel overdensities and significances. We need to go deeper into the Spitzer sample and acquire complete coverage of the most extreme Herschel overdensities (54 new fields). Such a unique sample has legacy value, and this is the last opportunity prior to JWST, WFIRST and Euclid.