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

We report on the mid-IR imaging at 7 and 10 m of the galaxy cluster Abell 370, obtained with the ... more We report on the mid-IR imaging at 7 and 10 m of the galaxy cluster Abell 370, obtained with the ISOCAM instrument onboard ESA's Infrared Space Observatory (ISO), as part of an ongoing program to image gravitational arcs and arclets in distant clusters. We have recorded initial detections of the A0 giant arc in both bandpasses, the two central dominant galaxies at 7 m, and several other cluster members and eld galaxies. These preliminary results are indicative of the potential output of our program when more extensive observational data become available.

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.

ESO Astrophysics Symposia, 1997

The Astrophysical Journal, 2012

The analysis of the physical properties of low-redshift Lyα emitters (LAEs) can provide clues in ... more The analysis of the physical properties of low-redshift Lyα emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z ∼ 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z ∼ 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z ∼ 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Lyα emission in their spectrum (non-LAEs). These results suggest that at z ∼ 0.3, Lyα photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z ∼ 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Lyα technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.

The Astrophysical Journal, 2011

We compare multi-wavelength star formation rate (SFR) indicators out to z ∼ 3 in the GOODS-South ... more We compare multi-wavelength star formation rate (SFR) indicators out to z ∼ 3 in the GOODS-South field. Our analysis uniquely combines U -to-8µm photometry from FIREWORKS, MIPS 24 µm and PACS 70, 100, and 160 µm photometry from the PEP survey, and Hα spectroscopy from the SINS survey. We describe a set of conversions that lead to a continuity across SFR indicators. A luminosityindependent conversion from 24 µm to total infrared luminosity yields estimates of L IR that are in the median consistent with the L IR derived from PACS photometry, albeit with significant scatter. Dust correction methods perform well at low to intermediate levels of star formation. They fail to recover the total amount of star formation in systems with large SF R IR /SF R UV ratios, typically occuring at the highest SFRs (SF R UV +IR 100 M ⊙ /yr) and redshifts (z 2.5) probed. Finally, we confirm that Hα-based SFRs at 1.5 < z < 2.6 are consistent with SF R SED and SF R UV +IR provided extra attenuation towards HII regions is taken into account (A V,neb = A V,continuum /0.44). With the cross-calibrated SFR indicators in hand, we perform a consistency check on the star formation histories inferred from SED modeling. We compare the observed SFR-M relations and mass functions at a range of redshifts to equivalents that are computed by evolving lower redshift galaxies backwards in time. We find evidence for underestimated stellar ages when no stringent constraints on formation epoch are applied in SED modeling. We demonstrate how resolved SED modeling, or alternatively deep UV data, may help to overcome this bias. The age bias is most severe for galaxies with young stellar populations, and reduces towards older systems. Finally, our analysis suggests that SFHs typically vary on timescales that are long (at least several 100 Myr) compared to the galaxies' dynamical time.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003

The X-ray astronomy satellite XMM-Newton has been in an orbit taking it through the trapped radia... more The X-ray astronomy satellite XMM-Newton has been in an orbit taking it through the trapped radiation belts and direct solar proton flux during the peak of the current solar cycle for over two and a half years. The MOS CCD detectors (E2 V CCD22's) have degraded in charge transfer efficiency (CTE) as a result of damage created by high energy protons. Corrections for CTE in ground software have managed to restore most of the energy loss generated by the trapping sites, but the detector energy resolution has widened due to imperfect correction methods and the statistical noise generated by charge trapping. The detectors have been at À100 C since launch, and they are qualified to operate down to À130 C. Similar CCDs have been irradiated on the ground with 10 MeV protons and it was believed that the devices in orbit, although irradiated by much lower fluxes for longer times should exhibit the same improved CTE at lower temperatures. There was also concern that contrary to test devices on the ground, the devices in orbit had been almost continually cold for over 2 years and many bright pixels had developed giving a signal even at À100 C, due possibly to radiation and the impact of micro-meteoroids. Cooling the CCDs in XMM to À120 C demonstrated the expected improvement, and we intend to run both MOS cameras at the new temperature later in the year. r

Monthly Notices of the Royal Astronomical Society, 2001

We present mid-and far-IR photometry of the high-redshift (z=4.69) dusty quasar BR1202-0725. The ... more We present mid-and far-IR photometry of the high-redshift (z=4.69) dusty quasar BR1202-0725. The quasar was detected in the near-IR, at a flux level (0.7±0.2 mJy) consistent with an average Radio-Quiet Quasar at it's redshift. Only upper limits for the emission were obtained in the far-IR. These upper limits, when combined with data from ground-based telescopes, are the first direct evidence for a turn-over in the far-IR emission and hence confirm that a black-body dominates the SED at FIR wavelengths. This black-body is most probably cool dust, constrained to have a temperature below 80K, for a β of 1.5.

Monthly Notices of the Royal Astronomical Society, 2013

In the local Universe, galaxy properties show a strong dependence on environment. In cluster core... more In the local Universe, galaxy properties show a strong dependence on environment. In cluster cores, early type galaxies dominate, whereas star-forming galaxies are more and more common in the outskirts. At higher redshifts and in somewhat less dense environments (e.g. galaxy groups), the situation is less clear. One open issue is that of whether and how the star formation rate (SFR) of galaxies in groups depends on the distance from the centre of mass. To shed light on this topic, we have built a sample of X-ray selected galaxy groups at 0 < z < 1.6 in various blank fields (ECDFS, COSMOS, GOODS). We use a sample of spectroscopically confirmed group members with stellar mass M > 10 10.3 M in order to have a high spectroscopic completeness. As we use only spectroscopic redshifts, our results are not affected by uncertainties due to projection effects. We use several SFR indicators to link the star formation (SF) activity to the galaxy environment. Taking advantage of the extremely deep mid-infrared Spitzer MIPS and far-infrared Herschel PACS observations, we have an accurate, broad-band measure of the SFR for the bulk of the star-forming galaxies. We use multi-wavelength SED fitting techniques to estimate the stellar masses of all objects and the SFR of the MIPS and PACS undetected galaxies. We analyse the dependence of the SF activity, stellar mass and specific SFR on the group-centric distance, up to z ∼ 1.6, for the first time. We do not find any correlation between the mean SFR and group-centric distance at any redshift. We do not observe any strong mass segregation either, in agreement with predictions from simulations. Our results suggest that either groups have a much smaller spread in accretion times with respect to the clusters and that the relaxation time is longer than the group crossing time.