D. Cesarsky

Bio: D. Cesarsky is an academic researcher from Max Planck Society. The author has contributed to research in topics: Spectral resolution & Bolometer. The author has an hindex of 5, co-authored 5 publications receiving 2625 citations.

The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submil- limetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform integral-field spectroscopy and imaging photom- etry in the 60−210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60−85 μ mo r 85−125 μ ma nd 125−210 μm, over a field of view of ∼1.75 � × 3.5 � , with close to Nyquist beam sampling in each band. In spectroscopy mode, it images afi eld of 47 �� × 47 �� , resolved into 5 × 5 pixels, with an instantaneous spectral coverage of ∼ 1500 km s −1 and a spectral resolution of ∼175 km s −1 . We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.

The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25 pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m, over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47"x47", resolved into 5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral resolution of ~175km/s. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the Performance Verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.

Warm Molecular Hydrogen and Ionized Neon in the HH 2 Outflow

Abstract: We report on spectro-imaging observations of the Herbig-Haro 2 outflow with the ISOCAM camera on board the Infrared Space Observatory. The [Ne II] 12.81 μm and [Ne III] 15.55 μm lines are detected only toward the jet working surface (HH 2H), consistent with the high excitation of this knot in the optical range, while H2 pure rotational emission is found all over the shocked region HH 2. The low-energy transition S(2) traces warm gas (T ~ 400 K) peaked toward knots E and F and extended ejecta (T ~ 250-380 K) with masses of a few times 10-3 M☉ in the high-velocity CO outflow extending between the powering source and HH 2. Such emission could arise from low-velocity C-type shocks (v 10-15 km s-1). The higher transitions S(3)-S(7) trace the emission of hot shocked gas (T = 1000-1400 K) from individual optical knots in the HH 2 region. The ortho-to-para (OTP) ratio exhibits large spatial variations between 1.2 (knot E) and 2.5 (knot H), well below its value at LTE. The emission of the S(3)-S(7) lines is well accounted for by planar C-shock models with a typical velocity Vs = 20-30 km s-1 propagating into a medium of density ni = 104-105 cm-3 with an initial OTP ratio close to 1 in the preshock gas. In the leading edge of the jet, where the geometry of the emission allows a simple modeling, a good agreement is found with velocities derived from the optical proper motions measured in the ionized gas.

Shock-induced PDR in the Herbig-Haro object HH 2

Abstract: We report mid-infrared ($5-17\mu m$) and SO, CO, $^{13}$CO millimeter line observations of the protostellar jet HH~2 and the parental molecular cloud. We have detected for the first time mid-infrared emission along a protostellar jet. We find that the outflowing gas extends much further away than the Herbig-Haro object HH~2, showing direct evidence that downstream gas has been accelerated by previous outflow events. These gas layers appear to have been detached from the parental cloud, as they are distributed around a cavity, probably dug by protostellar outflow(s). SO emission is detected in shocked gas regions associated with outflows. The UV field produced in the strong shock region HH~2H-A has produced a low-excitation Photon-Dominated Region at the walls of the cavity, which is detected in the PAH emission bands and in the continuum between 5 and $17\mu m$. This continuum arises from very small grains transiently heated by a FUV field G $\simeq 20G_0$, which probably formed from evaporation of dust grain mantles in shocks.

Disks around hot stars in the Trifid nebula

Abstract: We report on mid-IR observations of the central region in the Trid nebula, carried out with ISOCAM in several broad-band infrared lters and in the low resolution spectroscopic mode provided by the circular variable lter. Analysis of the emission indicates the presence of a hot dust component (500 to 1000 K) and a warm dust component at lower temperatures (150 200 K) around several members of the cluster exciting the HII region, and other stars undetected at optical wavelengths. Complementary VLA observations suggest that the mid-IR emission could arise from a dust cocoon or a circumstellar disk, evaporated under the ionization of the central source and the exciting star of the nebula. In several sources the 9:7 m silicate band is seen in emission. One young stellar source shows indications of crystalline silicates in the circumstellar dust.

Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy

Abstract: Herschel was launched on 14 May 2009, and is now an operational ESA space observatory o ering unprecedented observational capabilities in the far-infrared and submillimetre spectral range 55 671 m. Herschel carries a 3.5 metre diameter passively cooled Cassegrain telescope, which is the largest of its kind and utilises a novel silicon carbide technology. The science payload comprises three instruments: two direct detection cameras/medium resolution spectrometers, PACS and SPIRE, and a very high-resolution heterodyne spectrometer, HIFI, whose focal plane units are housed inside a superfluid helium cryostat. Herschel is an observatory facility operated in partnership among ESA, the instrument consortia, and NASA. The mission lifetime is determined by the cryostat hold time. Nominally approximately 20,000 hours will be available for astronomy, 32% is guaranteed time and the remainder is open to the worldwide general astronomical community through a standard competitive proposal procedure.

The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submil- limetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform integral-field spectroscopy and imaging photom- etry in the 60−210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60−85 μ mo r 85−125 μ ma nd 125−210 μm, over a field of view of ∼1.75 � × 3.5 � , with close to Nyquist beam sampling in each band. In spectroscopy mode, it images afi eld of 47 �� × 47 �� , resolved into 5 × 5 pixels, with an instantaneous spectral coverage of ∼ 1500 km s −1 and a spectral resolution of ∼175 km s −1 . We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.

Star Formation in the Milky Way and Nearby Galaxies

Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

The Herschel-SPIRE instrument and its in-flight performance

Abstract: The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera and spectrometer It contains a three-band imaging photometer operating at 250, 350 and 500 mu m, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 mu m (447-1550 GHz) The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 03 K The photometer has a field of view of 4' x 8', observed simultaneously in the three spectral bands Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired The spectrometer has an approximately circular field of view with a diameter of 26' The spectral resolution can be adjusted between 12 and 25 GHz by changing the stroke length of the FTS scan mirror Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 15-2

From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey

Abstract: We summarize the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with the SPIRE and PACS cameras reveal a wealth of filamentary structure, as well as numerous dense cores embedded in the filaments. Between ~ 350 and 500 prestellar cores and ~ 45-60 Class 0 protostars can be identified in the Aquila field, while ~ unbound starless cores and no protostars are observed in the Polaris field. The prestellar core mass function (CMF) derived for the Aquila region bears a strong resemblance to the stellar initial mass function (IMF), already confirming the close connection between the CMF and the IMF with much better statistics than earlier studies. Comparing and contrasting our Herschel results in Aquila and Polaris, we propose an observationally-driven scenario for core formation according to which complex networks of long, thin filaments form first within molecular clouds, and then the densest filaments fragment into a number of prestellar cores via gravitational instability.