Bolometers at CEA: ARTEMIS and beyond Kern, P.; Revéret, V.; Talvard, M. ...
EAS publications series,
2009, 2009-00-00, 20090101, Letnik:
37
Journal Article
ArTeMiS is a bolometer camera that will be installed at the APEX submillimeter telescope in Chile in 2010. This instrument will be a powerful tool for scientists with its three focal planes that will ...operate simultaneously in background limited conditions at 200, 350 and 450 microns (5760 pixels in total). A prototype called p-ArTeMiS has been tested at APEX in 2007 and thanks to its good performances, the team has been able to conduct scientific projects in star formation and on debris disks. This paper summarises the details of the ArTeMiS project, with a description of the detectors, the optics, the cryogenics and the electronics. We will also present the undergoing studies at CEA on detectors for the future submillimeter space missions.
Context.The THz atmospheric “windows”, centered at roughly 1.3 and 1.5 THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N II line at 205 μm, and ...the ground transition of para-H2D+. The CO lines are tracers of hot (several 100 K), dense gas; N II is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20 K), dense gas. Aims.As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. Methods.CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. Results.The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical $T_{\rm rec}=1600$ K and spectral Allan variance times of ~30 s. CONDOR's “first light” observations of CO 13-12 emission from the hot core Orion FIR 4 (= OMC1 South) revealed a narrow line with $T_{\rm MB}\approx 210$ K and $\Delta V\approx 5.4$ km s-1. A search for N II emission from the ionization front of the Orion Bar resulted in a non-detection. Conclusions.The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.
CONDOR, the CO, N+, Deuterium Observations Receiver, is designed to make velocity-resolved observations of the CO, NII, and p-H2D+ lines in the 1.4 THz (200-240μm) atmospheric windows. CONDOR's first ...light observations were made with the APEX telescope in November 2005. The CONDOR beam on APEX (at ν = 1.5 THz) was expected to consist of a 4.3″ main beam and a 73″ error beam; this beam structure was verified from scans of Mars. The pointing accuracy, also determined from Mars scans, was better than 7″. The average atmospheric transmission during our Orion observations (elev~57°) was 19 ± 4% along the line-of-sight. A forward efficiency of Feff = 0.8 was determined from sky dips, and observations of the Moon and Mars were used to couple the CONDOR beam to sources of different sizes (ηc = 0.40 and ~0.10, respectively). For more information, see Wiedner et al. 2006.
Photon dominated regions in NGC 3603 Röllig, M.; Kramer, C.; Rajbahak, C. ...
Astronomy and astrophysics (Berlin),
01/2011, Letnik:
525
Journal Article
Recenzirano
Odprti dostop
Aims. We aim at deriving the excitation conditions of the interstellar gas as well as the local FUV intensities in the molecular cloud surrounding NGC 3603 to get a coherent picture of how the gas is ...energized by the central stars. Methods. The NANTEN2-4 m submillimeter antenna is used to map the CI 1–0, 2–1 and CO 4–3, 7–6 lines in a 2′ × 2′ region around the young OB cluster NGC 3603 YC. These data are combined with C18O 2–1 data, HIRES-processed IRAS 60 μm and 100 μm maps of the FIR continuum, and Spitzer/IRAC maps. Results. The NANTEN2 observations show the presence of two molecular clumps located south-east and south-west of the cluster and confirm the overall structure already found by previous CS and C18O observations. We find a slight position offset of the peak intensity of CO and CI, and the atomic carbon appears to be further extended compared to the molecular material. We used the HIRES far-infrared dust data to derive a map of the FUV field heating the dust. We constrain the FUV field to values of χ = 3−6 × 103 in units of the Draine field across the clouds. Approximately 0.2 to 0.3% of the total FUV energy is re-emitted in the CII 158 μm cooling line observed by ISO. Applying LTE and escape probability calculations, we derive temperatures (TMM1 = 43 K, TMM2 = 47 K), column densities (NMM1 = 0.9 × 1022 cm-2, NMM2 = 2.5 × 1022 cm-2) and densities (nMM1 = 3 × 103 cm-3, nMM2 = 103−104 cm-3) for the two observed molecular clumps MM1 and MM2. Conclusions. The cluster is strongly interacting with the ambient molecular cloud, governing its structure and physical conditions. A stability analysis shows the existence of gravitationally collapsing gas clumps which should lead to star formation. Embedded IR sources have already been observed in the outskirts of the molecular cloud and seem to support our conclusions.
Context. Star formation at earlier cosmological times took place in an interstellar medium with low metallicity. The Large Magellanic Cloud (LMC) is ideally suited to study star formation in such an ...environment. Aims. The physical and chemical state of the ISM in a star forming environment can be constrained by observations of submm and FIR spectral lines of the main carbon carrying species, CO, C i and C ii, which originate in the surface layers of molecular clouds illuminated by the UV radiation of the newly formed, young stars. Methods. We present high-angular resolution sub-millimeter observations in the N159W region in the LMC obtained with the NANTEN2 telescope of the 12CO J = 4 $\to$ 3, J = 7 $\to$ 6, and 13CO J = 4 $\to$ 3 rotational and C I 3P$_1-^3$P0 and 3P$_2-^3$P1 fine-structure transitions. The 13CO J = 4 $\to$ 3 and C i 3P$_2-^3$P1 transitions are detected for the first time in the LMC. We derive the physical and chemical properties of the low-metallicity molecular gas using an escape probability code and a self-consistent solution of the chemistry and thermal balance of the gas in the framework of a clumpy cloud PDR model. Results. The separate excitation analysis of the submm CO lines and the carbon fine structure lines shows that the emitting gas in the N159W region has temperatures of about 80 K and densities of about 104 cm-3. The estimated C to CO abundance ratio close to unity is substantially higher than in dense massive star-forming regions in the Milky Way. The analysis of all observed lines together, including the C ii line intensity reported in the literature, in the context of a clumpy cloud PDR model constrains the UV intensity to about $\chi \approx$ 220 and an average density of the clump ensemble of about 105 cm-3, thus confirming the presence of high density material in the LMC N159W region.
Clumpy photon-dominated regions in Carina Kramer, C.; Cubick, M.; Röllig, M. ...
Astronomy and astrophysics (Berlin),
01/2008, Letnik:
477, Številka:
2
Journal Article
Context.The Carina region is an excellent astrophysical laboratory for studying the feedback mechanisms of newly born, very massive stars within their natal giant molecular clouds (GMCs) at only ...2.35 kpc distance. Aims.We use a clumpy PDR model to analyse the observed intensities of atomic carbon and CO and to derive the excitation conditions of the gas. Methods.The NANTEN2-4 m submillimeter telescope was used to map the C I 3P1-3P0, 3P2-3P1 and CO 4–3, 7–6 lines in two 4'$\times$4' regions of Carina where molecular material interfaces with radiation from the massive star clusters. One region is the northern molecular cloud near the compact OB cluster Tr 14, and the second region is in the molecular cloud south of η Car and Tr 16. These data were combined with 13CO SEST spectra, HIRES/IRAS 60 μm and 100 μm maps of the FIR continuum, and maps of 8 μm IRAC/Spitzer and MSX emission. Results.We used the HIRES far-infrared dust data to create a map of the FUV field heating the gas. The northern region shows an FUV field of a few 103 in Draine units while the field of the southern region is about a factor 10 weaker. While the IRAC 8$\,\mu$m emission lights up at the edges of the molecular clouds, CO and also C I appear to trace the H2 gas column density. The northern region shows a complex velocity and spatial structure, while the southern region shows an edge-on PDR with a single Gaussian velocity component. We constructed models consisting of an ensemble of small spherically symmetric PDR clumps within the $38''$ beam (0.43 pc), which follow canonical power-law mass and mass-size distributions. We find that an average local clump density of 2$\times$105 cm-3 is needed to reproduce the observed line emission at two selected interface positions. Conclusions.Stationary, clumpy PDR models reproduce the observed cooling lines of atomic carbon and CO at two positions in the Carina Nebula.
Context. The Carina region is an excellent astrophysical laboratory for studying the feedback mechanisms of newly born, very massive stars within their natal giant molecular clouds (GMCs) at only ...2.35 kpc distance. Aims. We use a clumpy PDR model to analyse the observed intensities of atomic carbon and CO and to derive the excitation conditions of the gas. Methods. The NANTEN2-4 m submillimeter telescope was used to map the C I super(3) P sub(1)- super(3) P sub(0), super(3) P sub(2)- super(3) P sub(1) and CO 4-3, 7-6 lines in two 4'\times4' regions of Carina where molecular material interfaces with radiation from the massive star clusters. One region is the northern molecular cloud near the compact OB cluster Tr 14, and the second region is in the molecular cloud south of eta Car and Tr 16. These data were combined with super(13) CO SEST spectra, HIRES/IRAS 60 mum and 100 mum maps of the FIR continuum, and maps of 8 mum IRAC/Spitzer and MSX emission. Results. We used the HIRES far-infrared dust data to create a map of the FUV field heating the gas. The northern region shows an FUV field of a few 10 super(3) in Draine units while the field of the southern region is about a factor 10 weaker. While the IRAC 8\,\mum emission lights up at the edges of the molecular clouds, CO and also C I appear to trace the H sub(2) gas column density. The northern region shows a complex velocity and spatial structure, while the southern region shows an edge-on PDR with a single Gaussian velocity component. We constructed models consisting of an ensemble of small spherically symmetric PDR clumps within the 38'' beam (0.43 pc), which follow canonical power-law mass and mass-size distributions. We find that an average local clump density of 2\times10 super(5) cm super(-3) is needed to reproduce the observed line emission at two selected interface positions. Conclusions. Stationary, clumpy PDR models reproduce the observed cooling lines of atomic carbon and CO at two positions in the Carina Nebula.
PDF
