We present infrared spectra covering the wavelength ranges 3.1-5.0 m and 5.8-11.6 m for 9 young stars located in the Chamaeleon I dark cloud. The spectra were taken with the spectrophotometer of ISO (ISOPHOT-S). The spectra of three stars... more
We present infrared spectra covering the wavelength ranges 3.1-5.0 m and 5.8-11.6 m for 9 young stars located in the Chamaeleon I dark cloud. The spectra were taken with the spectrophotometer of ISO (ISOPHOT-S). The spectra of three stars which illuminate reflection nebulae are dominated by the series of strong emission features generally ascribed to polycyclic aromatic hydrocarbons. Three or possibly four stars classified as T Tauri stars show the 10 m silicate band in emis- sion, whereas another object, T42, shows the silicate band in absorption and could b eaTT austar with a disk seen edge-on. The last source, Cha IRN, is a deeply embedded young stellar object. Its spectrum is characterized by deep absorption bands due to various interstellar ices, but shows a very weak silicate band only.
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We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (≤ 100 Myr), nearby (≤ 1 kpc) stellar clusters mainly to detect young transiting... more
We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (≤ 100 Myr), nearby (≤ 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on timescales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e.g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R=16.5 mag with sufficient precision of 50 milli-mag rms (5 mmag rms down to R=14.5 mag) to detect transits, so that we can expect at least about one young transiti...
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We present a comprehensive study of the luminous young stellar object IRAS 12326-6245 at nearand mid-infrared wavelengths as well as in the millimetre wavelength range. IRAS 12326-6245 is associated with two ultracompact H ii regions.... more
We present a comprehensive study of the luminous young stellar object IRAS 12326-6245 at nearand mid-infrared wavelengths as well as in the millimetre wavelength range. IRAS 12326-6245 is associated with two ultracompact H ii regions. These massive young stellar objects are surrounded by a cluster of stars revealed by the near-infrared images. With N andQ-band imaging, we find four very deeply embedded mid-infrared sources which form a remarkable proto-Trapezium system. Both ultracompact H ii regions are associated with midinfrared sources. In addition, a K ′-band nebulosity is present which outlines the rim of the molecular outflow. The mapping in different molecular lines as well as in the λ 1.3 mm continuum shows that IRAS 12326-6245 is deeply embedded in a dense molecular cloud core in agreement with the steeply rising infrared spectral energy distributions of the ultracompact Hii regions. In the region one of the most energetic and massive bipolar molecular outflows was detecte...
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Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Using the IRAM array, we... more
Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Using the IRAM array, we obtained high angular resolution (about 1.5") observations with a high S/N per channel of the 13CO J=2-1 and C18O J=2-1 and of the 13CO J=1-0 lines. A standard parametric disk model is used to fit the line data in the Fourier-plane and to derive the CO disk properties. Our measurement is based on a detailed analysis of the spectroscopic profile from the CO disk rotating in Keplerian velocity. The millimeter continuum, tracing the dust, is also analyzed. We detect an inner cavity of radius 19 +/-4 AU at the 4.5 sigma level. Its origin remains unclear, but can be linked to planet formation or to a low mass stellar companion orbiting close to the central star (around 5-15 AU). The frequent finding of inner cavities suggests that either binarity is ...
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Context. We describe and benchmark two sophisticated chemical models developed by the Heidelberg and Bordeaux astrochemistry groups. Aims. The main goal of this study is to elaborate on a few well-described tests for state-of-the-art... more
Context. We describe and benchmark two sophisticated chemical models developed by the Heidelberg and Bordeaux astrochemistry groups. Aims. The main goal of this study is to elaborate on a few well-described tests for state-of-the-art astrochemical codes covering a range of physical conditions and chemical processes, in particular those aimed at constraining current and future interferometric observations of protoplanetary disks. Methods. We considered three physical models: a cold molecular cloud core, a hot core, and an outer region of a T Tauri disk. Our chemical network (for both models) is based on the original gas-phase osu_03_2008 ratefile and includes gas-grain interactions and a set of surface reactions for the H-, O-, C-, S-, and N-bearing molecules. The benchmarking was performed with the increasing complexity of the considered processes: (1) the pure gas-phase chemistry, (2) the gas-phase chemistry with accretion and desorption, and (3) the full gas-grain model with surfa...
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We present a study of the region around the intermediate-mass young stellar object NGC 2264 IRS1. This sourceisembeddedinadensecloudcore.Infraredimagesinthe J,H,andK bandshowajet-likestructureconnectedwithIRS1 as well as a second very... more
We present a study of the region around the intermediate-mass young stellar object NGC 2264 IRS1. This sourceisembeddedinadensecloudcore.Infraredimagesinthe J,H,andK bandshowajet-likestructureconnectedwithIRS1 as well as a second very deeply embedded small star cluster to the southeastern side. IRS1 itself is surrounded by a number of embedded low-mass stars. We mapped this area in various CS transitions, CO 3!2, some methanol lines and in C 18 O2 !1. The mapping results clearly show a second cloud clump cen- tered at the small star cluster. Two molecular outflows were found in the observed region. One flow is oriented along our line of sight and associated with IRS1 and the other flow is centered at the small star cluster. Several additional spectral line settings were taken at the IRS1positiontogetmoreaccurateconstraintsonthegastemper- atureanddensity.Thesedata,aswellasthemaps,wereanalysed with statistical equilibrium excitation calculations. The best t results give an uniform tem...
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We have performed a submillimeter survey of the areas around 47 selected IRAS point sources of high luminosity. A number of new submm sources were found. The high multiplicity of the sources suggests that isolated massive-star formation... more
We have performed a submillimeter survey of the areas around 47 selected IRAS point sources of high luminosity. A number of new submm sources were found. The high multiplicity of the sources suggests that isolated massive-star formation is a rare event. In some cases the filaments near the young stellar objects (YSO) or between them were found. The pointers of
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The IRAM PdBI array was used to observe 12CO(2-1) at 1.3mm configurations, resulting in spectral line maps with 1.5" resolution. We use an empirical parameterized steady-state outflow model combined with 2-D line radiative transfer... more
The IRAM PdBI array was used to observe 12CO(2-1) at 1.3mm configurations, resulting in spectral line maps with 1.5" resolution. We use an empirical parameterized steady-state outflow model combined with 2-D line radiative transfer calculations and chi2-minimization in parameter space to derive a best-fit model and constrain parameters of the outflow. (1 data file).
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The paper will review the observational properties of very young massive stars. Strategies to find the earliest stages of massive star formation will be discussed. Results of ISO observations of very young massive stars will be presented... more
The paper will review the observational properties of very young massive stars. Strategies to find the earliest stages of massive star formation will be discussed. Results of ISO observations of very young massive stars will be presented including the spectral energy distribution of the massive class 0 object CB 3-mm.
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In the course of a comprehensive millimeter/submillimeter survey of massive-star-forming regions, the vicinities of a sample of 47 luminous IRAS sources were closely investigated with the Submillimeter Common-User Bolometric Array and the... more
In the course of a comprehensive millimeter/submillimeter survey of massive-star-forming regions, the vicinities of a sample of 47 luminous IRAS sources were closely investigated with the Submillimeter Common-User Bolometric Array and the MPIfR bolometers in order to search for massive protostellar candidates. A particularly interesting object has been found in the surroundings of the bright far-infrared source IRAS 07029-1215. Follow-up line observations show that the object is cold, has a massive envelope, and is associated with an energetic molecular outflow. No infrared point source has been detected at its position. Therefore, it is a very good candidate as a member of the long-sought group of massive protostars.
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... th (K) (5) 5 25.4 22.9 25.0 53.3 12 19.7 22.2 20.1 50.7 70 17.6 20.2 17.9 38.1 150 15.9 17.9 16.2 33.8 tim. ... Dr. H. Meyerdierks ofthe Royal Observatory in Edinburgh, Scotland, and the staffofthe Helsinki University ofTechnology,... more
... th (K) (5) 5 25.4 22.9 25.0 53.3 12 19.7 22.2 20.1 50.7 70 17.6 20.2 17.9 38.1 150 15.9 17.9 16.2 33.8 tim. ... Dr. H. Meyerdierks ofthe Royal Observatory in Edinburgh, Scotland, and the staffofthe Helsinki University ofTechnology, Finland, helped with the Effelsberg and Metsähovi ...
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We studied three members of the sample of 31 cold and luminous southern IRAS sources, which was compiled by Osterloh et al. (1997). These young stellar objects are characterized by extremely red IRAS colours [Snu (100 mu m) > Snu (60... more
We studied three members of the sample of 31 cold and luminous southern IRAS sources, which was compiled by Osterloh et al. (1997). These young stellar objects are characterized by extremely red IRAS colours [Snu (100 mu m) > Snu (60 mu m) > Snu (25 mu m) > 20xSnu (12 mu m)]. Based on their strong CO line wings found in previous observations, the three objects IRAS 12091-6129, IRAS 12405-6238, and IRAS 16019-4903 were selected in order to investigate their nature and the outflow structure in more detail. The mapping in the CO J = 2->1 line as well as the lambda 1.3 mm continuum dust emission show that all three sources are deeply embedded in dense cloud cores. Strong CO line wings and their mapping indicate the presence of bipolar gas outflows in all three cases. N- and Q-band imaging resolve some substructures inside the lambda 1.3 mm maps and give evidence for deeply embedded young stellar objects which seem to drive the observed outflows. The comparison of the FIR ima...
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We present a comprehensive study of the luminous young stellar object IRAS 12326-6245 at near- and mid-infrared wavelengths as well as in the millimetre wavelength range. IRAS 12326-6245 is associated with two ultracompact H ii regions.... more
We present a comprehensive study of the luminous young stellar object IRAS 12326-6245 at near- and mid-infrared wavelengths as well as in the millimetre wavelength range. IRAS 12326-6245 is associated with two ultracompact H ii regions. These massive young stellar objects are surrounded by a cluster of stars revealed by the near-infrared images. With N- and Q-band imaging, we find
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We have performed a submillimeter survey of the areas around 47 selected IRAS point sources of high luminosity. A number of new submm sources were found. The high multiplicity of the sources suggests that isolated massive-star formation... more
We have performed a submillimeter survey of the areas around 47 selected IRAS point sources of high luminosity. A number of new submm sources were found. The high multiplicity of the sources suggests that isolated massive-star formation is a rare event. In some cases the filaments near the young stellar objects (YSO) or between them were found. The pointers of
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Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Using the IRAM array, we... more
Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Using the IRAM array, we obtained high angular resolution (about 1.5") observations with a high S/N per channel of the 13CO J=2-1 and C18O J=2-1 and of the 13CO J=1-0 lines. A standard parametric disk model is used to fit the line data in the Fourier-plane and to derive the CO disk properties. Our measurement is based on a detailed analysis of the spectroscopic profile from the CO disk rotating in Keplerian velocity. The millimeter continuum, tracing the dust, is also analyzed. We detect an inner cavity of radius 19 +/-4 AU at the 4.5 sigma level. Its origin remains unclear, but can be linked to planet formation or to a low mass stellar companion orbiting close to the central star (around 5-15 AU). The frequent finding of inner cavities suggests that either binarity is ...
Research Interests:
We present a study of the region around the intermediate-mass young stellar object NGC 2264 IRS1. This sourceisembeddedinadensecloudcore.Infraredimagesinthe J,H,andK bandshowajet-likestructureconnectedwithIRS1 as well as a second very... more
We present a study of the region around the intermediate-mass young stellar object NGC 2264 IRS1. This sourceisembeddedinadensecloudcore.Infraredimagesinthe J,H,andK bandshowajet-likestructureconnectedwithIRS1 as well as a second very deeply embedded small star cluster to the southeastern side. IRS1 itself is surrounded by a number of embedded low-mass stars. We mapped this area in various CS transitions, CO 3!2, some methanol lines and in C18 O2 !1. The mapping results clearly show a second cloud clump cen- tered at the small star cluster. Two molecular outflows were found in the observed region. One flow is oriented along our line of sight and associated with IRS1 and the other flow is centered at the small star cluster. Several additional spectral line settings were taken at the IRS1positiontogetmoreaccurateconstraintsonthegastemper- atureanddensity.Thesedata,aswellasthemaps,wereanalysed with statistical equilibrium excitation calculations. The best t results give an uniform temp...
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The unique capabilities of the Spitzer Instrument MIPS are used to investigate the mid to far infrared properties of candidates for the earliest stages of massive star formation: pre-protocluster cores and protoclusters. These candidates... more
The unique capabilities of the Spitzer Instrument MIPS are used to investigate the mid to far infrared properties of candidates for the earliest stages of massive star formation: pre-protocluster cores and protoclusters. These candidates are selected from millimeter continuum surveys where the targets are conspicuous compact cloud cores. The youth of the selected cores is underlined by being non detected at NIR and MIR wavelengths so far. The proposed MIPS observations (24 & 70 micron photometry and SED) will reveal the SED of these pre-protocluster cores or protoclusters. The shape of the SED and the luminosity allow to draw conclusions about the central object(s) embedded in the cores and the temperature and density structure of the cores. 3D radiative transfer models are available to help with the analysis. The analysis of the Spitzer data will enable us to identify the protoclusters and pre-protocluster cores in our sample and to derive the properties of these earliest stages of...
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The millimeter continuum maps were collected at three observatories: the Heinrich Hertz Submillimeter Telescope (SMT, Mount Graham, Arizona), the Institut de Radioastronomie Millimetrique (IRAM) 30m telescope (Pico Veleta, Spain), and the... more
The millimeter continuum maps were collected at three observatories: the Heinrich Hertz Submillimeter Telescope (SMT, Mount Graham, Arizona), the Institut de Radioastronomie Millimetrique (IRAM) 30m telescope (Pico Veleta, Spain), and the James Clerk Maxwell Telescope (JCMT, Mauna Kea, Hawaii). (3 data files).
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We present results of the observations of 17 molecular clouds associated with bright FIR sources in the NH3 (1, 1) and (2, 2) lines with the 100-m radio telescope in Effelsberg. The lines were detected in 11 clouds and 10 of them have... more
We present results of the observations of 17 molecular clouds associated with bright FIR sources in the NH3 (1, 1) and (2, 2) lines with the 100-m radio telescope in Effelsberg. The lines were detected in 11 clouds and 10 of them have been mapped in these lines. The kinetic temperatures, sizes, masses and mean densities of the ammonia cores have been derived. For most of the detected clouds the masses derived under the assumption of a relative ammonia abundance of chi(NH3)=3x10-8 are close to virial masses. However, in S 88 B the ratio M/Mvir is only ~0.1 and in a few other cases this ratio is significantly lower than unity which may indicate ammonia underabundance. Almost all objects with the signs of underabundance are among the most luminous IR sources in our sample. Most of the mapped cores are elongated with noticeable velocity gradients along the major axis. The most prominent example is S 255. S 87 has a two-component structure with 2 distinct velocity components which overla...
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Context: Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Aims: We attempt... more
Context: Recent modeling based on unresolved infrared observations of the spectral energy distribution (SED) of GM Aurigae suggests that the inner disk of this single TTauri star is truncated at an inner radius of 25 AU. Aims: We attempt to find evidence of this inner hole in the gas distribution, using spectroscopy with high angular resolution. Methods: Using the IRAM
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Résumé/Abstract Context. We describe and benchmark two sophisticated chemical models developed by the Heidelberg and Bordeaux astrochemistry groups. Aims. The main goal of this study is to elaborate on a few well-described tests for... more
Résumé/Abstract Context. We describe and benchmark two sophisticated chemical models developed by the Heidelberg and Bordeaux astrochemistry groups. Aims. The main goal of this study is to elaborate on a few well-described tests for state-of-the-art astrochemical codes covering a range of physical conditions and chemical processes, in particular those aimed at constraining current and future interferometric observations of protoplanetary disks. Methods. We considered three physical models: a cold molecular cloud core, a hot core, ...