| 1. |
- Olofsson, Sven, 1933-, et al.
(författare)
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A new method of determining distances to dark globules. : The distance to B 335
- 2009
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 498:2, s. 455-461
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Tidskriftsartikel (refereegranskat)abstract
- Context. The distance to an isolated dark globule is often unknown and yet crucial for understanding its properties, in particular its mass. A new approach to this problem is discussedAims. The purpose of the present paper is to investigate how well the distances of more or less reddened field stars can be determined by using multi-colour imaging.Methods. We observed a test globule, B 335 in U, B, g, r, and I, and together with the 2MASS survey, this data set gives a well-defined spectral energy distribution (SED) of a large number of stars. The SED of each star depends on the interstellar extinction, the distance to the star, and its intrinsic SED. As we had good reasons to suspect that the wavelength dependence of the extinction (the reddening) changes from the outskirts of the globule to the central parts, we did not assume any specific reddening law. Instead, we use a scheme that allows independent determination of the extinction in each line of sight as determined by groups of adjacent stars. The method is based on the use of stellar atmospheric models to represent the intrinsic SEDs of the stars. Formally, it is then possible to determine the spectral class of each star and thereby its distance. For some of the stars we have optical spectra, allowing us to compare the photometric classification to the spectrometric. Results. As expected, the main problem is that there are few stars found within each distance bin for the small field size defining a typical dark globule. However, the characterisation of the extinction and photometric classification give consistent results and we can identify one star at the front side of the globule. It has a photometric distance of 90 pc. The closest star behind the B 335 globule has a distance of only 120 pc and we therefore determine the distance to B 335 as 90-120 pc. Our deep U image shows a relatively bright south-western rim of the globule, and we investigate whether it might be due to a local enhancement of the radiation field. A candidate source, located 1.5 arcmin outside our field, would be the field star, HD 184982. This star has an entry in the Hipparcos Catalogue and its distance is 140-200 pc. However, we come to the conclusion that the bright SW rim is more likely due to the wing of the point-spread-function (PSF) of this star.
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| 2. |
- Gålfalk, Magnus, et al.
(författare)
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Herbig-Haro flows in B335
- 2007
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 475:1, s. 281-300
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Tidskriftsartikel (refereegranskat)abstract
- Aims.To study the Herbig-Haro flows in the nearby dark globule B335. To find new HH objects and H2 knots, make a proper motion map of the flow activity and investigate physical properties through shock models. Methods: We have observed optical (Hα and [SII]) and near-IR (2.12 μm H2) deep fields and taken optical spectra using the 2.56 m Nordic Optical Telescope, as well as a near-UV deep field (U band) using the 3.58 m NTT. In addition we present new SPITZER / IRAC (3.5-8.0 μm) and MIPS (24 μm) observations. We use previous Hα and 2.12 μm H2 observations taken 15 and 9 years earlier to make proper motion maps. We then investigate the shock physics by matching our spectra with planar shock models. Results: We discover five new HH objects (HH 119 D-H) in the eastern and one (HH 119 I) in the western lobe of the outflow. From proper motions we find an optically bright, roughly E-W oriented group with high space velocities (200-280 km s-1) and a near-IR bright, slower group (15-75 km s-1) moving to the ESE. We also find a system of at least 15 H2 knots in the western lobe. This (WNW) counterflow suggests the possibility of a binary outflow source, giving rise to two outflow axes with slightly different orientations. We find that the E-W flow is symmetrical with evidence for two outbursts. We make the first detection of [OI] λλ 6300/63 in HH 119 B and Hβ in HH 119 A and B and find their extinctions to be AV ≈ 1.4 and 4.4, respectively. HH 119 A is found to expand much faster than expected from linear expansion with distance from the outflow source. Using planar shock models we find shock velocities of ~60 km s-1 (A) and ~35 km s-1 (B and C). This agrees with A being of higher excitation than B and C. In our U image we detect three of the HH objects and propose that the emission arise from the [OII] λ3728 line and the blue continuum. New SPITZER / IRAC and MIPS observations show most of the HH objects at 4.5 μm and a E-W elongated hour-glass shaped structure at the outflow source. Even at 24 μm it is not clear whether most of the light is direct or reflected. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based on observations made with the New Technology Telescope, ESO (La Silla) under programme ID 077.C-0524. NOT and NTT images in FITS format are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/475/281
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| 3. |
- Kurita, K., et al.
(författare)
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Recent Development Status of PoGOLite
- 2009
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Ingår i: Astrophysics with All-Sky X-Ray Observations. ; , s. 386-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Olofsson, Göran, 1944-
(författare)
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The SPIRE Instrument
- 2009
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Ingår i: EAS Publications Series. - : EDP Sciences. - 1633-4760 .- 1638-1963. ; 34, s. 33-42
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- SPIRE, the Spectral and Photometric Imaging Receiver, is Herschel's submillimetre camera and spectrometer. It comprises a three-band imaging photometer operating at 250, 350 and 500 µm, and an imaging Fourier Transform Spectrometer (FTS) covering 194–672 µm. The design of SPIRE is described, and the expected scientific performance is summarised, based on modelling and flight instrument test results.
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