The field-imaging far-infrared line spectrometer (FIFI-LS) is a science instrument for the Strato... more The field-imaging far-infrared line spectrometer (FIFI-LS) is a science instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA). FIFI-LS allows simultaneous observations in two spectral channels. The “blue” channel is sensitive from 51[Formula: see text][Formula: see text]m to 125[Formula: see text][Formula: see text]m and the “red” channel from 115[Formula: see text][Formula: see text]m to 203[Formula: see text][Formula: see text]m. The instantaneous spectral coverage is 1000–3000[Formula: see text]km/s in the blue and 800–2500[Formula: see text]km/s in the red channel with a spectral resolution between 150[Formula: see text]km/s and 600[Formula: see text]km/s. Each spectral channel observes a field of five by five spatial pixels on the sky. The pixel size in the blue channel is 6.14 by 6.25 square arc seconds and it is 12.2 by 12.5 square arc seconds in the red channel. FIFI-LS has been operating on SOFIA since 2014. It is available to the astronomical communit...
Proceedings of the International Astronomical Union, 2015
The Orion Nebula is the closest massive star forming region allowing us to study the physical con... more The Orion Nebula is the closest massive star forming region allowing us to study the physical conditions in such a region with high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the atomic and molecular gas in the Orion Nebula at medium spectral resolution. The large maps obtained with FIFI-LS cover the nebula from the BN/KL-object to the bar in several fine structure lines. They allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud with unprecedented detail. Another investigation targeted the molecular gas in the BN/KL region of the Orion Nebula, which is stirred up by a violent explosion about 500 years ago. The explosion drives a wide angled molecular outflow. We present maps of several high-J CO observations, allowing us to analyze the heated molecular gas.
Proceedings of the International Astronomical Union, 2015
We have selected cold and massive (M > 100M ⊙) cores as candidates for early phases of star fo... more We have selected cold and massive (M > 100M ⊙) cores as candidates for early phases of star formation from millimeter continuum surveys without associations at short wavelengths. We compared the millimeter continuum peak positions with IR and radio catalogs and excluded cores that had sources associated with the cores’ peaks. We compiled a list of 173 cores in over 117 regions that are candidates for very early phases of Massive Star Formation (MSF). Now with the Spitzer and Herschel archives, these cores can be characterized further. We are compiling this data set to construct the complete spectral energy distribution (SED) in the mid- and far-infrared with good spatial resolution and broad spectral coverage. This allow us to disentangle the complex regions and model the SED of the deeply embedded protostars/clusters. We present a status report of our efforts: a preview of the IR properties of all cores and their embedded source inferred from a grey body fit to the compiled SEDs.
Ground-based and Airborne Instrumentation for Astronomy VI, 2016
FIFI-LS (the Field Imaging Far Infrared Line Spectrometer for SOFIA) was successfully commissione... more FIFI-LS (the Field Imaging Far Infrared Line Spectrometer for SOFIA) was successfully commissioned in 2014 during six flights on SOFIA. The observed wavelengths are set by rotating reflective gratings. In flight these gratings and their rotating mechanisms are exposed to vibrations. To quantify these vibrations, an acceleration sensor was placed on the exterior of the instrument. Simultaneously, the angle sensor of the grating was read out to analyze the movement of the grating. Based on this data, lab measurements were conducted to evaluate the effect of the vibrations on the image quality of FIFI-LS. The submitted paper will present the measured data and show the results of the analysis.
Observatory Operations: Strategies, Processes, and Systems VI, 2016
Observing on the Stratospheric Observatory for Infrared Astronomy (SOFIA) requires a strategy tha... more Observing on the Stratospheric Observatory for Infrared Astronomy (SOFIA) requires a strategy that takes the specific circumstances of an airborne platform into account. Observations of a source cannot be extended or shortened on the spot due to flight path constraints. Still, no exact prediction of the time on source is available since there are always wind and weather conditions, and sometimes technical issues. Observations have to be planned to maximize the observing efficiency while maintaining full flexibility for changes during the observation. The complex nature of observations with FIFI-LS - such as the interlocking cycles of the mechanical gratings, telescope nodding and dithering - is considered in the observing strategy as well. Since SOFIA Cycle 3 FIFI-LS is available to general investigators. Therefore general investigators must be able to define the necessary parameters simply, without being familiar with the instrument, still resulting in efficient and flexible observations. We describe the observing process with FIFI-LS including the integration time estimate, the mapping and dithering setup and aspects of the scripting for the actual observations performed in flight. We also give an overview of the observing scenarios, which have proven to be useful for FIFI-LS.
In the course of a comprehensive mm/submm survey of massive star-forming regions, a particularly ... more In the course of a comprehensive mm/submm survey of massive star-forming regions, a particularly interesting object has been found in the surroundings of the bright FIR source IRAS 07029-1215, in a distance of 1 kpc. The object-named UYSO 1 (Unidentified Young Stellar Object 1)-is cold (T = 40 K), it has a massive envelope, and it is associated with an energetic molecular outflow. No infrared point source has been detected at its position for λ ≤ 20 µm. Therefore, it is a very good candidate for a member of the long searched for group of massive protostars.
The paper will review the observational properties of very young massive stars. Strategies to fin... 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.
ABSTRACT FIFI LS is a far-infrared integral field spectrometer for SOFIA that maximizes observing... more ABSTRACT FIFI LS is a far-infrared integral field spectrometer for SOFIA that maximizes observing efficiency by spectrally imaging fields in two medium velocity resolution bands simultaneously and nearly independently. Although the two observing bands, Red (110-210 microns) and Blue (42-110 microns), share some common fore-optics, the Field-Imaging Far-Infrared Line Spectrometer (FIFI LS) can observe diffraction-limited spectra at R = 1400 to 6500, depending on wavelength, with two separate Littrow mounted spectrometers. To further increase the observing efficiency, we employ an integral field technique that allows multiplexing spatially. This is achieved by utilizing slicer mirrors to optically re-arrange the 2D field into a single slit for a standard long slit spectrometer. Effectively, a 5 × 5 pixel spatial field of view is imaged to a 25 × 1 pixel slit and dispersed to a 25 × 16 pixel, 2D detector array. The detectors are two large format Ge:Ga arrays, axially stressed in the Red channel to achieve a longer wavelength response and slightly stressed in the Blue channel. Overall, for each of the 25 spatial pixels in each band, the instrument can cover a velocity range of approximately 1500 km/s with an estimated sensitivity of 2 × x 10-15 W Hz1/2 per pixel. This arrangement provides good spectral coverage with high responsivity. With this scheme FIFI LS will have advantages over single-slit spectrometers in detailed morphological studies of the heating and cooling of galaxies, star formation, the ISM under low-metalicity conditions as found in dwarf galaxies, active galactic nuclei and their environment, starbursts, and merging/interacting galaxies.
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying... more The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 5-40 µm imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60-240 µm, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.3-1.1 µm imager, developed at Lowell Observatory. FLITECAM is a 1-5 µm wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42-210 µm integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 5-28 µm high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50-240 µm imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011.
Ground-based and Airborne Instrumentation for Astronomy V, 2014
ABSTRACT FIFI-LS is the German far-infrared integral field spectrometer for the SOFIA airborne ob... more ABSTRACT FIFI-LS is the German far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument offers medium resolution spectroscopy (R ~ a few 1000) in the far-infrared with two independent spectrometers covering 50-110 and 100-200 μm. The integral field units of the two spectrometers obtain spectra covering concentric square fields-of-views sized 3000and 6000, respectively. Both spectrometers can observe simultaneously at any wavelength in their ranges making efficient mapping of far-infrared lines possible. FIFI-LS has been commissioned at the airborne observatory SOFIA as a PI instrument in spring 2014. During 2015, the commissioning as facility instrument will be complete and the SOFIA observatory will take over the operation of FIFI-LS. The instrument can already be used by the community. Primary science cases are the study of the galactic and extra-galactic interstellar medium and its processes. In this presentation, the capabilities of FIFI-LS on the SOFIA telescope will be explained and how they are used by the offered observing modes. The remaining atmosphere and the warm telescope create a high background situation, which requires a differential measurement technique. This is achieved by SOFIA’s chopping secondary mirror and nodding the telescope. Depending on the source size, different observing modes may be used to observe a source. All modes use spatial and spectral dithering. The resulting data products will be 3D-data cubes. The observing parameters will be specified using AOTs, like the other SOFIA instruments, and created via the tool SSPOT which is similar to the Spitzer Space Telescope SPOT tool. The observations will be done in service mode, but SOFIA invites a few investigators to fly onboard SOFIA during (part of) their observations.
We describe the design of the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS), operated as... more We describe the design of the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS), operated as a Facility-Class instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA). FIFI-LS is an imaging spectrometer for medium resolution spectroscopy. Since being commissioned in 2014, it has performed over 50 SOFIA commissioning and science°ights. After operating as a principal investigator instrument in 2014 and early 2015, it was accepted as a Facility Science Instrument in 2015. In addition to the description of the design, we report on the in-°ight performance and the concept of operation. We also provide an overview of the science opportunities with FIFI-LS and describe how FIFI-LS observations complement and complete observations with the PACS instrument on the Herschel observatory.
The unique capabilities of the Spitzer Instrument MIPS are used to investigate the mid to far inf... 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...
We present the first mid-infrared (MIR) detection of a field brown dwarf (BD) and the first groun... more We present the first mid-infrared (MIR) detection of a field brown dwarf (BD) and the first ground-based MIR measurements of a disk around a young BD candidate. We prove the absence of warm dust surrounding the field BD LP 944-20. In the case of the young BD candidate Cha Hα2, we find clear evidence for thermal dust emission from a disk. Surprisingly, the object does not exhibit any silicate feature as previously predicted. We show that the flat spectrum can be explained by an optically thick flat dust disk.
In the course of a comprehensive mm/submm survey of massive star-forming regions, the vicinities ... more In the course of a comprehensive mm/submm survey of massive star-forming regions, the vicinities of a sample of 47 luminous IRAS sources were closely investigated with SCUBA and IRAM bolometers in order to search for massive protostellar candidates. A particularly interesting object has been found in the surroundings of the bright FIR source IRAS 07029-1215. Follow-up line observations show that the object is cold, that it has a massive envelope, and that it is associated with an energetic molecular outflow. No infrared point source has been detected at its position. Therefore, it is a very good candidate for a member of the long searched-for group of massive protostars.
We present BIMA and SCUBA observations of the young cluster associated with BD + 40 • 4124 in the... more We present BIMA and SCUBA observations of the young cluster associated with BD + 40 • 4124 in the dense molecular gas tracer CS J = 2 → 1 and the continuum dust continuum at λ = 3.1 mm and λ = 850 µm. The dense gas and dust in the system is aligned into a long ridge morphology extending ∼0.4 pc with 16 gas clumps of estimated masses ranging from 0.14-1.8 M ⊙. A northsouth variation in the CS center line velocity can be explained with a two cloud model. We posit that the BD+40 • 4124 stellar cluster formed from a cloud-cloud collision. The largest linewidths occur near V1318 Cyg-S, a massive star affecting its natal environment. In contrast, the dense gas near the other, more evolved, massive stars displays no evidence for disruption; the material must either be processed into the star, dissipate, or relax, fairly quickly. The more evolved lowmass protostars are more likely to be found near the massive stars. If the majority of low-mass stars are coeval, the seemingly evolved low-mass protostars are not older: the massive stars have eroded their structures. Finally, at the highest resolution, the λ = 3.1 mm dust emission is resolved into a flattened structure 3100 by 1500 AU with an estimated mass of 3.4 M ⊙. The continuum and CS emission are offset by 1. ′′ 1 from the southern binary source. A simple estimate of the extinction due to the continuum emission structure is A V ∼ 700 mag. From the offset and as the southern source is detected in the optical, the continuum emission is from a previously unknown very young, intermediate-mass, embedded stellar object.
Monthly Notices of the Royal Astronomical Society, 2011
We present observations of the intermediate to massive star-forming region I05345+3157 using the ... more We present observations of the intermediate to massive star-forming region I05345+3157 using the molecular line tracer CS(2-1) with the Combined Array for Research in Millimetrewave Astronomy to reveal the properties of the dense gas cores. Seven gas cores are identified in the integrated intensity map of CS(2-1). Among these, cores 1 and 3 have counterparts in the λ = 2.7 mm continuum data. We suggest that cores 1 and 3 are star-forming cores that may already or will very soon harbour young massive protostars. The total masses of core 1 estimated from the local thermodynamic equilibrium (LTE) method and dust emission by assuming a gas-to-dust ratio are 5 ± 1 and 18 ± 6 M , and that of core 3 are 15 ± 7 and 11 ± 3 M , respectively. The spectrum of core 3 shows blue-skewed self-absorption, which suggests gas infall-a collapsing core. The observed broad linewidths of the seven gas cores indicate non-thermal motions. These non-thermal motions can be interactions with nearby outflows or due to the initial turbulence; the former is observed, while the role of the initial turbulence is less certain. Finally, the virial masses of the gas cores are larger than the LTE masses, which, for a bound core, implies a requirement on the external pressure of ∼10 8 K cm −3. The cores have the potential to further form massive stars.
Our search for the earliest stages of massive star formation turned up twelve massive pre-protocl... more Our search for the earliest stages of massive star formation turned up twelve massive pre-protocluster candidates plus a few protoclusters. For this search, we selected 47 FIR-bright IRAS sources in the outer Galaxy. We mapped regions of several square arcminutes around the IRAS source in the millimeter continuum in order to find massive cold cloud cores possibly being in a very early stage of massive star formation. Masses and densities are derived for the 128 molecular cloud cores found in the obtained maps. We present these maps together with near-infrared, mid-infrared, and radio data collected from the 2MASS, MSX, and NVSS catalogs. Further data from the literature on detections of high-density tracers, outflows, and masers are added. The multi-wavelength datasets are used to characterize each observed region. The massive cloud cores (M > 100 M ⊙) are placed in a tentative evolutionary sequence depending on their emission at the investigated wavelengths. Candidates for the youngest stages of massive star formation are identified by the lack of detections in the above-mentioned nearinfrared, mid-infrared, and radio surveys. Twelve massive cores prominent in the millimeter continuum fulfill this requirement. Since neither FIR nor radio emission have been detected from these cloud cores massive protostars must be very deeply embedded in these cores. Some of these objects may actually Pre-Proto-cluster cores: an up to now rare object class, where the initial conditions of massive star formation can be studied.
The field-imaging far-infrared line spectrometer (FIFI-LS) is a science instrument for the Strato... more The field-imaging far-infrared line spectrometer (FIFI-LS) is a science instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA). FIFI-LS allows simultaneous observations in two spectral channels. The “blue” channel is sensitive from 51[Formula: see text][Formula: see text]m to 125[Formula: see text][Formula: see text]m and the “red” channel from 115[Formula: see text][Formula: see text]m to 203[Formula: see text][Formula: see text]m. The instantaneous spectral coverage is 1000–3000[Formula: see text]km/s in the blue and 800–2500[Formula: see text]km/s in the red channel with a spectral resolution between 150[Formula: see text]km/s and 600[Formula: see text]km/s. Each spectral channel observes a field of five by five spatial pixels on the sky. The pixel size in the blue channel is 6.14 by 6.25 square arc seconds and it is 12.2 by 12.5 square arc seconds in the red channel. FIFI-LS has been operating on SOFIA since 2014. It is available to the astronomical communit...
Proceedings of the International Astronomical Union, 2015
The Orion Nebula is the closest massive star forming region allowing us to study the physical con... more The Orion Nebula is the closest massive star forming region allowing us to study the physical conditions in such a region with high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the atomic and molecular gas in the Orion Nebula at medium spectral resolution. The large maps obtained with FIFI-LS cover the nebula from the BN/KL-object to the bar in several fine structure lines. They allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud with unprecedented detail. Another investigation targeted the molecular gas in the BN/KL region of the Orion Nebula, which is stirred up by a violent explosion about 500 years ago. The explosion drives a wide angled molecular outflow. We present maps of several high-J CO observations, allowing us to analyze the heated molecular gas.
Proceedings of the International Astronomical Union, 2015
We have selected cold and massive (M > 100M ⊙) cores as candidates for early phases of star fo... more We have selected cold and massive (M > 100M ⊙) cores as candidates for early phases of star formation from millimeter continuum surveys without associations at short wavelengths. We compared the millimeter continuum peak positions with IR and radio catalogs and excluded cores that had sources associated with the cores’ peaks. We compiled a list of 173 cores in over 117 regions that are candidates for very early phases of Massive Star Formation (MSF). Now with the Spitzer and Herschel archives, these cores can be characterized further. We are compiling this data set to construct the complete spectral energy distribution (SED) in the mid- and far-infrared with good spatial resolution and broad spectral coverage. This allow us to disentangle the complex regions and model the SED of the deeply embedded protostars/clusters. We present a status report of our efforts: a preview of the IR properties of all cores and their embedded source inferred from a grey body fit to the compiled SEDs.
Ground-based and Airborne Instrumentation for Astronomy VI, 2016
FIFI-LS (the Field Imaging Far Infrared Line Spectrometer for SOFIA) was successfully commissione... more FIFI-LS (the Field Imaging Far Infrared Line Spectrometer for SOFIA) was successfully commissioned in 2014 during six flights on SOFIA. The observed wavelengths are set by rotating reflective gratings. In flight these gratings and their rotating mechanisms are exposed to vibrations. To quantify these vibrations, an acceleration sensor was placed on the exterior of the instrument. Simultaneously, the angle sensor of the grating was read out to analyze the movement of the grating. Based on this data, lab measurements were conducted to evaluate the effect of the vibrations on the image quality of FIFI-LS. The submitted paper will present the measured data and show the results of the analysis.
Observatory Operations: Strategies, Processes, and Systems VI, 2016
Observing on the Stratospheric Observatory for Infrared Astronomy (SOFIA) requires a strategy tha... more Observing on the Stratospheric Observatory for Infrared Astronomy (SOFIA) requires a strategy that takes the specific circumstances of an airborne platform into account. Observations of a source cannot be extended or shortened on the spot due to flight path constraints. Still, no exact prediction of the time on source is available since there are always wind and weather conditions, and sometimes technical issues. Observations have to be planned to maximize the observing efficiency while maintaining full flexibility for changes during the observation. The complex nature of observations with FIFI-LS - such as the interlocking cycles of the mechanical gratings, telescope nodding and dithering - is considered in the observing strategy as well. Since SOFIA Cycle 3 FIFI-LS is available to general investigators. Therefore general investigators must be able to define the necessary parameters simply, without being familiar with the instrument, still resulting in efficient and flexible observations. We describe the observing process with FIFI-LS including the integration time estimate, the mapping and dithering setup and aspects of the scripting for the actual observations performed in flight. We also give an overview of the observing scenarios, which have proven to be useful for FIFI-LS.
In the course of a comprehensive mm/submm survey of massive star-forming regions, a particularly ... more In the course of a comprehensive mm/submm survey of massive star-forming regions, a particularly interesting object has been found in the surroundings of the bright FIR source IRAS 07029-1215, in a distance of 1 kpc. The object-named UYSO 1 (Unidentified Young Stellar Object 1)-is cold (T = 40 K), it has a massive envelope, and it is associated with an energetic molecular outflow. No infrared point source has been detected at its position for λ ≤ 20 µm. Therefore, it is a very good candidate for a member of the long searched for group of massive protostars.
The paper will review the observational properties of very young massive stars. Strategies to fin... 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.
ABSTRACT FIFI LS is a far-infrared integral field spectrometer for SOFIA that maximizes observing... more ABSTRACT FIFI LS is a far-infrared integral field spectrometer for SOFIA that maximizes observing efficiency by spectrally imaging fields in two medium velocity resolution bands simultaneously and nearly independently. Although the two observing bands, Red (110-210 microns) and Blue (42-110 microns), share some common fore-optics, the Field-Imaging Far-Infrared Line Spectrometer (FIFI LS) can observe diffraction-limited spectra at R = 1400 to 6500, depending on wavelength, with two separate Littrow mounted spectrometers. To further increase the observing efficiency, we employ an integral field technique that allows multiplexing spatially. This is achieved by utilizing slicer mirrors to optically re-arrange the 2D field into a single slit for a standard long slit spectrometer. Effectively, a 5 × 5 pixel spatial field of view is imaged to a 25 × 1 pixel slit and dispersed to a 25 × 16 pixel, 2D detector array. The detectors are two large format Ge:Ga arrays, axially stressed in the Red channel to achieve a longer wavelength response and slightly stressed in the Blue channel. Overall, for each of the 25 spatial pixels in each band, the instrument can cover a velocity range of approximately 1500 km/s with an estimated sensitivity of 2 × x 10-15 W Hz1/2 per pixel. This arrangement provides good spectral coverage with high responsivity. With this scheme FIFI LS will have advantages over single-slit spectrometers in detailed morphological studies of the heating and cooling of galaxies, star formation, the ISM under low-metalicity conditions as found in dwarf galaxies, active galactic nuclei and their environment, starbursts, and merging/interacting galaxies.
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying... more The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 5-40 µm imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60-240 µm, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.3-1.1 µm imager, developed at Lowell Observatory. FLITECAM is a 1-5 µm wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42-210 µm integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 5-28 µm high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50-240 µm imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011.
Ground-based and Airborne Instrumentation for Astronomy V, 2014
ABSTRACT FIFI-LS is the German far-infrared integral field spectrometer for the SOFIA airborne ob... more ABSTRACT FIFI-LS is the German far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument offers medium resolution spectroscopy (R ~ a few 1000) in the far-infrared with two independent spectrometers covering 50-110 and 100-200 μm. The integral field units of the two spectrometers obtain spectra covering concentric square fields-of-views sized 3000and 6000, respectively. Both spectrometers can observe simultaneously at any wavelength in their ranges making efficient mapping of far-infrared lines possible. FIFI-LS has been commissioned at the airborne observatory SOFIA as a PI instrument in spring 2014. During 2015, the commissioning as facility instrument will be complete and the SOFIA observatory will take over the operation of FIFI-LS. The instrument can already be used by the community. Primary science cases are the study of the galactic and extra-galactic interstellar medium and its processes. In this presentation, the capabilities of FIFI-LS on the SOFIA telescope will be explained and how they are used by the offered observing modes. The remaining atmosphere and the warm telescope create a high background situation, which requires a differential measurement technique. This is achieved by SOFIA’s chopping secondary mirror and nodding the telescope. Depending on the source size, different observing modes may be used to observe a source. All modes use spatial and spectral dithering. The resulting data products will be 3D-data cubes. The observing parameters will be specified using AOTs, like the other SOFIA instruments, and created via the tool SSPOT which is similar to the Spitzer Space Telescope SPOT tool. The observations will be done in service mode, but SOFIA invites a few investigators to fly onboard SOFIA during (part of) their observations.
We describe the design of the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS), operated as... more We describe the design of the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS), operated as a Facility-Class instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA). FIFI-LS is an imaging spectrometer for medium resolution spectroscopy. Since being commissioned in 2014, it has performed over 50 SOFIA commissioning and science°ights. After operating as a principal investigator instrument in 2014 and early 2015, it was accepted as a Facility Science Instrument in 2015. In addition to the description of the design, we report on the in-°ight performance and the concept of operation. We also provide an overview of the science opportunities with FIFI-LS and describe how FIFI-LS observations complement and complete observations with the PACS instrument on the Herschel observatory.
The unique capabilities of the Spitzer Instrument MIPS are used to investigate the mid to far inf... 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...
We present the first mid-infrared (MIR) detection of a field brown dwarf (BD) and the first groun... more We present the first mid-infrared (MIR) detection of a field brown dwarf (BD) and the first ground-based MIR measurements of a disk around a young BD candidate. We prove the absence of warm dust surrounding the field BD LP 944-20. In the case of the young BD candidate Cha Hα2, we find clear evidence for thermal dust emission from a disk. Surprisingly, the object does not exhibit any silicate feature as previously predicted. We show that the flat spectrum can be explained by an optically thick flat dust disk.
In the course of a comprehensive mm/submm survey of massive star-forming regions, the vicinities ... more In the course of a comprehensive mm/submm survey of massive star-forming regions, the vicinities of a sample of 47 luminous IRAS sources were closely investigated with SCUBA and IRAM bolometers in order to search for massive protostellar candidates. A particularly interesting object has been found in the surroundings of the bright FIR source IRAS 07029-1215. Follow-up line observations show that the object is cold, that it has a massive envelope, and that it is associated with an energetic molecular outflow. No infrared point source has been detected at its position. Therefore, it is a very good candidate for a member of the long searched-for group of massive protostars.
We present BIMA and SCUBA observations of the young cluster associated with BD + 40 • 4124 in the... more We present BIMA and SCUBA observations of the young cluster associated with BD + 40 • 4124 in the dense molecular gas tracer CS J = 2 → 1 and the continuum dust continuum at λ = 3.1 mm and λ = 850 µm. The dense gas and dust in the system is aligned into a long ridge morphology extending ∼0.4 pc with 16 gas clumps of estimated masses ranging from 0.14-1.8 M ⊙. A northsouth variation in the CS center line velocity can be explained with a two cloud model. We posit that the BD+40 • 4124 stellar cluster formed from a cloud-cloud collision. The largest linewidths occur near V1318 Cyg-S, a massive star affecting its natal environment. In contrast, the dense gas near the other, more evolved, massive stars displays no evidence for disruption; the material must either be processed into the star, dissipate, or relax, fairly quickly. The more evolved lowmass protostars are more likely to be found near the massive stars. If the majority of low-mass stars are coeval, the seemingly evolved low-mass protostars are not older: the massive stars have eroded their structures. Finally, at the highest resolution, the λ = 3.1 mm dust emission is resolved into a flattened structure 3100 by 1500 AU with an estimated mass of 3.4 M ⊙. The continuum and CS emission are offset by 1. ′′ 1 from the southern binary source. A simple estimate of the extinction due to the continuum emission structure is A V ∼ 700 mag. From the offset and as the southern source is detected in the optical, the continuum emission is from a previously unknown very young, intermediate-mass, embedded stellar object.
Monthly Notices of the Royal Astronomical Society, 2011
We present observations of the intermediate to massive star-forming region I05345+3157 using the ... more We present observations of the intermediate to massive star-forming region I05345+3157 using the molecular line tracer CS(2-1) with the Combined Array for Research in Millimetrewave Astronomy to reveal the properties of the dense gas cores. Seven gas cores are identified in the integrated intensity map of CS(2-1). Among these, cores 1 and 3 have counterparts in the λ = 2.7 mm continuum data. We suggest that cores 1 and 3 are star-forming cores that may already or will very soon harbour young massive protostars. The total masses of core 1 estimated from the local thermodynamic equilibrium (LTE) method and dust emission by assuming a gas-to-dust ratio are 5 ± 1 and 18 ± 6 M , and that of core 3 are 15 ± 7 and 11 ± 3 M , respectively. The spectrum of core 3 shows blue-skewed self-absorption, which suggests gas infall-a collapsing core. The observed broad linewidths of the seven gas cores indicate non-thermal motions. These non-thermal motions can be interactions with nearby outflows or due to the initial turbulence; the former is observed, while the role of the initial turbulence is less certain. Finally, the virial masses of the gas cores are larger than the LTE masses, which, for a bound core, implies a requirement on the external pressure of ∼10 8 K cm −3. The cores have the potential to further form massive stars.
Our search for the earliest stages of massive star formation turned up twelve massive pre-protocl... more Our search for the earliest stages of massive star formation turned up twelve massive pre-protocluster candidates plus a few protoclusters. For this search, we selected 47 FIR-bright IRAS sources in the outer Galaxy. We mapped regions of several square arcminutes around the IRAS source in the millimeter continuum in order to find massive cold cloud cores possibly being in a very early stage of massive star formation. Masses and densities are derived for the 128 molecular cloud cores found in the obtained maps. We present these maps together with near-infrared, mid-infrared, and radio data collected from the 2MASS, MSX, and NVSS catalogs. Further data from the literature on detections of high-density tracers, outflows, and masers are added. The multi-wavelength datasets are used to characterize each observed region. The massive cloud cores (M > 100 M ⊙) are placed in a tentative evolutionary sequence depending on their emission at the investigated wavelengths. Candidates for the youngest stages of massive star formation are identified by the lack of detections in the above-mentioned nearinfrared, mid-infrared, and radio surveys. Twelve massive cores prominent in the millimeter continuum fulfill this requirement. Since neither FIR nor radio emission have been detected from these cloud cores massive protostars must be very deeply embedded in these cores. Some of these objects may actually Pre-Proto-cluster cores: an up to now rare object class, where the initial conditions of massive star formation can be studied.
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Papers by Randolf Klein