Publications (18)17.39 Total impact
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Article: GM 2-4 - a signpost for low and intermediate mass star formation
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ABSTRACT: We present a multi-wavelength study of the region towards the GM 2-4 nebula and the nearby source IRAS 05373+2340. Our near-infrared H2 1-0 S(1) line observations reveal various shock-excited features which are part of several bipolar outflows. We identify candidates for the driving sources of the outflows from a comparison of the multi-waveband archival data-sets and SED modelling. The SED spectral slope (\alpha(IRAC)) for all the protostars in the field was then compared with the visual extinction map. This comparison suggests that star formation is progressing from NE to SW across this region.Monthly Notices of the Royal Astronomical Society 10/2011; 418(3):1994-2003. · 4.90 Impact Factor -
Dataset: Figure.4
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ABSTRACT: Close-up view in H2 1-0 S(1) emission of the area surrounding the IRAS 05373+2349 and the near-infrared cluster where numerous MHOs where identified. Positions of IRS4 and 5 are marked with crosses on all panels. Panel (a) reveals details of MHO 734, 739, 740, 744 and 745. Panel (b) shows the suggested outflow structure with dotted arrows. Overlaid contours are from the 3.6cm emission starting from 3� and climbing with a 3� step-size and are from the data published by Molinari et al. (2002). Positions of 3.6cm peaks are marked with CM-A, -B and -C. -
Dataset: Figure.2
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ABSTRACT: Close-up view of GM 2-4 and IRAS 05373+2349 including the region where new molecular hydrogen emission line objects (MHOs) are found. Class I sources reported by Gutermuth et al. (2009) are marked with a crosses on all panels. Panel (a) is optical [SII] image where Herbig-Haro objects discovered by (Nikogossian et al. 2009) are marked along with the GM 2-4, GGD 4a and IRAS 05373+2349 error ellipse. Panel (b) is near-infrared H2 1-0 S(1) line+continuum image where the MHOs are marked with squares. Panel (c) shows Spitzer IRAC colour-composite image constructed from 3.6�m (blue), 4.5�m (green) and 8.0�m (red) bands with positions of newly detected MHOs marked with squares for a comparison. For this particular case the brightest (mostly saturated) stars in the field were truncated in order to stretch the colour scheme and reveal relatively fainter objects. -
Dataset: Figure.3
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ABSTRACT: Area containing the MHO 735, 736 and 737. Positions of IRS objects are marked with the crosses on all panels. Dotted arrow on both panels show the possible outflow direction. Panel (a) shows the H2 1-0 S(1) emission. Panel (b) is a colour composite image constructed from 3.6�m (blue), 4.5�m (green) and 8.0�m (red) Spitzer IRAC bands where the position of MHO 735 is marked with a filled circle for an easy comparison and a dotted bow-shock outlines the MHO 737. -
Dataset: Figure.7
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ABSTRACT: Spectral energy distribution (SED) of IRS3 to IRS7. Filled circles are the data points and the triangles are lower and upper limits where errors are generally smaller than the data points. The solid black line indicates the best-fitting model, and the grey lines show all models that also fit the data satisfying the Chi^2 - Chi^2 best < 3 per data point criteria. The dashed line shows the SED of the assumed stellar photosphere in the best-fitting model. -
Dataset: Figure.8
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ABSTRACT: The wide-field view of the region in H2 where offsets are measured from IRS4 and solid line box shows the area presented in Fig. 2(b).Overlaid contours are from AV map constructed from 2MASS PSC and provided by Rowles & Froebrich (2009). Filled circles indicate the positions of IRAC identified Class I/II YSO sources provided by Gutermuth et al. (2009) where the colour spans according to the range of IRAC SED Slope (Alpha^ IRAC). -
Dataset: Figure.1
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ABSTRACT: General field including GM 1-64 and GM 2-4 centred on IRAS 05373+2349. Panel (a) is DSS2 red image of the region overlaid with a visual extinction contours obtained from Dobashi et al. (2005) peaking at TGU H1314. The solid-line ellipse indicates the positional uncertainty of IRAS 05373+2349 and the green asterisks mark the positions of masers. Panel (b) is the 2MASS false colour composite view of the region constructed from J (blue), H (green) and Ks (red) bands. Overlaid are the IRAS 100�m contours at 50, 70, 90 and 110 MJy/sterad. Panel (c) is Spitzer IRAC colour composite image constructed from 3.6�m (blue), 4.5�m (green) and 8.0�m (red) bands. Stars marked with big and small circles are sources reported by Gutermuth et al. (2009) and classified as Class I protostars and Class II pre-main-sequence stars respectively. Panel (d) is Spitzer MIPS 24�m band view of the region where the same Class I sources are marked with the nomenclature used in our study. -
Dataset: Figure.5
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ABSTRACT: Scaled-up views of MHO 738 and 741 where the offsets are calculated from IRS4. Dotted-line arrows show the direction of the suggested bipolar outflow. Panel (a) shows the area including MHO 741 in H2 1-0 S(1) emission and the panel (b) is the same area in Spitzer IRAC composite view constructed from 3.6�m (blue), 4.5�m (green) and 8.0�m (red) bands. Panel (c) and panel (d) show the same wavelengths as in panels (a) and (b) but for the area including the MHO 738A, B and C. -
Article: An unbiased search for the signatures of protostars in the rho Ophiuchi Molecular Cloud. II. Millimetre continuum observations
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ABSTRACT: We have performed a 1 square degree 1.2mm dust continuum survey in the rho Oph molecular cloud. We detect a number of previously unknown sources, ranging from extended cores over compact, starless cores to envelopes surrounding young stellar objects of Class 0, Class I, and Class II type. We analyse the mass distribution, spatial distribution and the potential equilibrium of the cores. For the inner regions, the survey results are consistent with the findings of previous narrower surveys. The core mass function resembles the stellar initial mass function, with the core mass function shifted by a factor of two to higher masses (for the chosen opacity and temperature). In addition, we find no statistical variation in the core mass function between the crowded inner regions and those in more isolated fields except for the absence of the most massive cores in the extended cloud. The inner region contains compacter cores. This is interpreted as due to a medium of higher mean pressure although strong pressure variations are evident in each region. The cores display a hierarchical spatial distribution with no preferred separation scale length. However, the frequency distribution of nearest neighbours displays two peaks, one of which at 5000AU can be the result of core fragmentation. The orientations of the major axes of cores are consistent with an isotropic distribution. In contrast, the relative orientations of core pairs are preferentially in the NW-SE direction on all separation scales. These results are consistent with core production and evolution in a turbulent environment. We report a new low-mass Class 0 object and its CO outflow. Comment: accepted for publication in Astronomy and Astrophysics. Full .ps version available at http://www.ifa.hawaii.edu/users/stanke/preprints.htmlAstronomy and Astrophysics 11/2005; 447(2):609-622. · 4.59 Impact Factor -
Conference Proceeding: RNO53 region: Nest of high-mass outflows revealed
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ABSTRACT: We present results from series (Movsessian et al. 2003; Magakian et al.2005) of follow-up multi-band investigations of reflection nebulae firstly cataloged in mid 70s at the Byurakan Observatory (Gyulbudaghian et al. 1977;1978). In this poster we concentrate on two examples of our study: GM1-61 (RNO53) and GM2-4 (GGD4, HHL26). Both reflection nebulae are situated in the molecular cloud [KOY98] 183.7-03.6 at a distance of 2kpc. The area is well known for the presence of H20 masers and there has been considerable work done at far-infrared wavelengths revealing the high-luminosity IRAS source. Despite this, there were no investigations carried out here in the optical and at near-infrared wavelengths. Our observations in the optical detected series of strong [SII] line shocks and the follow-up near-infrared study reveals chains of H2 S(1) 1-0 line shocks pointing to the IRAS 05373+2349 (PSC) source.IAU Symposium 227 - Massive Star Birth: A Crossroads of Astrophysics, Acireale, Italy; 05/2005 -
Conference Proceeding: HELIX: A multinational project boosted by CAHA observations
CAHA Colloquium 2005, MPIA, Heidelberg, Germany; 04/2005 -
Article: The cores of rho Ophiuchus
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ABSTRACT: We search for dense cores and the molecular outflows which accompany stellar birth in the rho Ophiuchi cloud L1688 through two unbiased wide-field surveys. A solution to the problem of how to avoid the dissolution of brown dwarf binaries is suggested: binaries forming in the widely scattered low-mass cores are not susceptible to disruption since the region is dynamically relaxed. We also find weak H_2 outflows which may be driven by proto-brown-dwarfs. The dense cores are detected through continuum emission from associated dust grains at 1.2 mm. Covering over 1 square degree, we detect many previously unknown sources, ranging from extended cores to those harbouring Class II young stars. We analyse the mass and spatial distributions. The core mass function resembles the stellar initial mass function, both within the tightly-packed clumps as well as within the less-crowded surroundings. The cores display a hierarchical spatial distribution with no preferred separation scale length. The orientations of the major axes of cores are consistent with an isotropic distribution whereas the orientations of core pairs possess a preferential direction on all separation scales, consistent with the filamentary cloud appearance. Our near-infrared survey for molecular hydrogen emission covers 35 arcmin × 35 arcmin. We detect several new H_2 flows but the total number of detected outflows is low and is consistent with the paucity of Class 0 and Class 1 sources in the molecular cloud. Most of the candidate driving sources are deeply embedded in dense cores. A very young outflow arises from the newly discovered Class 0 source MMS 126. Flow directions are generally NE-SW, perpendicular to the above preferred direction. The apparent extents of molecular flows are related to either the widths or the separation between cloud filaments.Memorie della Societa Astronomica Italiana. 01/2005; 76:247. -
Article: Molecule destruction and formation in molecular clouds
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ABSTRACT: We show that supersonic turbulence accelerates the transition of an atomic cloud into a molecular cloud, quantified here through a demo model and 3D numerical simulations which explicitly include atomic-molecular chemistry. Specific sites where amplified formation may be detectable are suggested.Astrophysics and Space Science 04/2004; 289:333-336. · 1.69 Impact Factor -
Conference Proceeding: H2 outflows from Bok Globules detected with Omega Prime
CAHA Collowquium 2003, MPIA, Hedielberg, Germany; 05/2003 -
Article: A multi-epoch near-infrared study of the HH 7-11 protostellar outflow
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ABSTRACT: We present near-infrared observations of the protostellar outflow HH 7-11 in the molecular hydrogen 1-0 S(1) and [FeII]1.644- µm emission lines. Images at four epochs spread over 11 yr constrain the proper motions of the H2 emission knots to be less than 0.045 arcsec yr-1, corresponding to tangential speeds of under 47 km s-1 at 220-pc distance, consistent with the proper motions derived in the optical range for the atomic component. Reanalysis of previous observations shows that variability and distortion of the SVS 13 reference star led to erroneous high H2 proper motions. The SVS 13 K-band flux is a factor of 3 higher in 1994-2000 than in 1989. Numerous H2 subknots are identified on images taken in 1998 and 2000. No significant relative variability is found in these subknots, consistent with slow outflow evolution. Compact [FeII] emission peaks are found at the locations of atomic emission-line features observed in the optical range. We also identify in this line an elongated feature corresponding to the proposed jet Mach disc.Monthly Notices of the Royal Astronomical Society 04/2003; 338(1):57-66. · 4.90 Impact Factor -
Conference Proceeding: Can We Trace the Evolution in CB34?
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ABSTRACT: CB34 is a large Bok Globule, an isolated molecular cloud capable of forming a group of stars. We present near-infrared observations in order to learn about the origin and evolution of such large globules. Two long parallel trails of H2 knots (H and N) are discovered on wide-field images in the H2 1-0 S(1) emission line. These 1 parsec scale outflows extend to the outskirts of the globule where they disappear without the trace of bow shocks. This suggests that the outflows physically extend much further into a lower density ambient medium where their terminating bows cannot be detected. The two outflows are extremely well collimated and are parallel to within 3deg. JHK photometry yields the presence of a central concentration of reddened stars, and a lower density halo of less reddened stars within and associated with the globule. We sketch a picture for the star formation history of the globule in which two star phases have occurred.The Origins of Stars and Planets: The VLT View - ESO Workshop, Garching, Germany; 04/2001 -
Article: The Calar Alto Observatory — present and future instrumentation
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ABSTRACT: The Calar Alto Observatory, located at 2168 m altitude in the Sierra de los Filabres in southern Spanish province of Andalucia, was founded in the early 1970s in order to provide astronomers in Germany and in Spain with modern observational facilities in the northern hemisphere. This role is not going to change over the next decade as 2–4 m telescopes are still essential and more efficient than 8 m telescopes, for wide-field and surface-brightness limited surveys, for support of surveys at other wavelengths (X-ray, radio), for regular monitoring work, for pursuing innovative ideas, for obtaining accurate astrometry and photometry of reference objects and unknowns, etc. In order to pursue these challenges, state of the art instrumentation is required. In the following, the existing facilities on Calar Alto are summarised, and future instrumentation projects are briefly discussed.New Astronomy Reviews 45:33-36. · 1.32 Impact Factor -
Article: The Rosette Eye: the key transition phase in the birth of a massive star
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ABSTRACT: Massive protostars dramatically influence their surroundings via accretion-induced outflows and intense radiation fields. They evolve rapidly, the disk and infalling envelope being evaporated and dissipated in ~105 yr. Consequently, they are very rare and investigating this important phase of early stellar evolution is extremely difficult. Here we present the discovery of a key transient phase in the emergence of a massive young star, in which ultraviolet radiation from the newborn giant has just punctured through its natal core. The massive young stellar object AFGL 961 II is readily resolved in the near-infrared. Its morphology closely resembles a cat's eye and is here dubbed the ``Rosette Eye.'' Emerging ionized flows blow out an hourglass-shaped nebula, which, along with the existence of strong near-infrared excess, suggests the existence of an accretion disk in the perpendicular direction. The lobes of the hourglass, however, are capped with arcs of static H 2 emission produced by fluorescence. This study has strong implications for our understanding of how massive stars embark on their formation.The Astrophysical Journal, v.679, L101-L104 (2008).
