The SOFIA Telescope

The SOFIA telescope as the heart of the observatory is a major technological challenge. I present an overview on the astro-nomical and scientific requirements for such a big airborne observatory and demonstrate the impact of these requirements on the layout of SOFIA, in particular on the telescope design as it is now. Selected components of the telescope will be de-scribed in their context and functionality. The current status of the telescope is presented.Comment: 6 pages, 7 figures, to appear in: Proceedings of SPIE: Airborne Telescope Systems, Munich, March 2000, Vol. 4014, paper with high resolution figures available at http://astro1.ws.ba.dlr.de/WEBPAGES/paper.ht

Near-infrared integral-field spectroscopy of HD209458b

We present first results of an exploratory study to use integral field spectroscopy to observe extrasolar planets. We focus on transiting "Hot Jupiters" and emphasize the importance of observing strategy and exact timing. We demonstrate how integral field spectroscopy compares with other spectroscopic techniques currently applied. We have tested our concept with a time series observation of HD209458b obtained with SINFONI at the VLT during a superior conjunction.Comment: SPIE conference proceeding, Astronomical telescopes and instrumentation, Orlando, 200

Near infrared imaging spectroscopy of NGC1275

We present H and K band imaging spectroscopy of the core regions of the cD/AGN galaxy NGC1275. The spectra, including lines from H2, H, 12CO bandheads, [FeII], and [FeIII], are exploited to constrain the star formation and excitation mechanisms in the galaxy's nucleus. The near-infrared properties can largely be accounted for by ionized gas in the NLR, dense molecular gas, and hot dust concentrated near the active nucleus of NGC1275. The strong and compact H2 emission is mostly from circumnuclear gas excited by the AGN and not from the cooling flow. The extended emission of latetype stars is diluted in the center by the thermal emission of hot dust.Comment: 16 pages, LaTex, 15 gif figures, aa.cls required, accepted for A&A, high resolution images at http://astro1.ws.ba.dlr.d

NIR Imaging Spectroscopy of the Inner Few Arcseconds of NGC 4151 with OSIRIS at Keck

We present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive optics assisted near-infrared imaging field spectrograph OSIRIS at the Keck Observatory. The angular resolution is about a few parsecs on-site and thus competes easily with optical images taken previously with the Hubble Space Telescope. We present the morphology and dynamics of most species detected but focus on the morphology and dynamics of the narrow line region (as traced by emission of [FeII]1.644 m), the interplay between plasma ejected from the nucleus (as traced by 21 cm continuum radio data) and hot H2 gas and characterize the detected nuclear HeI2.058 m absorption feature as a narrow absorption line (NAL) phenomenon. Emission from the narrow line region (NLR) as traced by [FeII] reveals a biconical morphology and we compare the measured dynamics in the [FeII] emission line with models proposing acceleration of gas in the NLR and simple ejection of gas into the NLR. In the inner 2.5 arcseconds the acceleration model reveals a better fit to our data than the ejection model.We also see evidence that the jet very locally enhances emission in [FeII] at certain positions in our field-of-view such that we were able to distinct the kinematics of these clouds from clouds generally accelerated in the NLR. Further, the radio jet is aligned with the bicone surface rather than the bicone axis such that we assume that the jet is not the dominant mechanism responsible for driving the kinematics of clouds in the NLR. The hot H2 gas is thermal with a temperature of about 1700 K. We observe a remarkable correlation between individual H2 clouds at systemic velocity with the 21 cm continuum radio jet. We propose that the radio jet is at least partially embedded in the galactic disk of NGC 4151 such that deviations from a linear radio structure are invoked by interactions of jet plasma with H2 clouds that are moving into the path of the jet because of rotation of the galactic disk of NGC 4151. Additionally, we observe a correlation of the jet as traced by the radio data, with gas as traced in Br and H2, at velocities between systemic and +/- 200 km/s at several locations along the path of the jet. The HeI2.058 m line in NGC 4151 appears in emission with a blueshifted absorption component from an outflow. The emission (absorption) component has a velocity offset of 10 km/s (-280 km/s) with a Gaussian (Lorentzian) full-width (half-width) at half maximum of 160 km/s (440 km/s). The absorption component remains spatially unresolved and its kinematic measures differ from that of UV resonance absorption lines. From the amount of absorption we derive a lower limit of the HeI 2S column density of 1 10(exp 14) cm2 with a covering factor along the line-of-sight of C(sub los) approximately equal to 0.1

Sigma Orionis IRS1 A and B: A Binary Containing a Proplyd

We report optical and infrared imaging spectroscopy observations of the young binary object Sigma Orionis IRS1 A/B. The brighter component (Sigma Ori IRS1 A) of this binary system has M1 spectral type and a mass in the range of 0.3 to 0.8 solar masses. The fainter component (Sigma Ori IRS1 B) has a unique morphology and spectrum. The unresolved stellar object is surrounded by an extended envelope that is slightly offset from the position of this star. The envelope's spectrum shows strong emission lines of H and HeI but no shock-excited emission from molecular hydrogen or from [FeII]. The embedded stellar object Sigma Ori IRS1 B has an absorption spectrum characteristic of a late M photosphere, but with an additional approximately equal amount of dust continuum flux veiling the absorption lines. Sigma Ori IRS1 B is probably a young brown dwarf embedded in a proplyd that is being photo-evaporated by the UV flux of the nearby multiple O and B star system Sigma Ori.Comment: The paper has been accepted for publicaiton by The Astrophysical Journal Letters. It has 11 pages of text and 5 figure

Upgrading the field-imaging far-infrared line spectrometer for the Stratospheric Observatory for Infrared Astronomy (SOFIA) with KIDs: enabling large sample (extragalactic) surveys

We present the initial design, performance improvements and science opportunities for an upgrade to the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS). FIFI-LS efficiently measures fine structure cooling lines, delivering critical constraints of the interstellar medium and starforming environments. SOFIA provides the only FIR observational capability in the world, making FIFI-LS a workhorse for FIR lines, combining optimal spectral resolution and a wide velocity range. Its continuous coverage from 51-203 microns makes FIFI-LS a versatile tool to investigate a multitude of diagnostic lines within our galaxy and in extragalactic environments. The sensitivity and field-of-view (FOV) of FIFI-LS are limited by its 90s-era photoconductor arrays. These limits can be overcome by upgrading the instrument using the latest developments in Kinetic Inductance Detectors (KIDs). KIDs provide sensitivity gains in excess of 1.4 and allow larger arrays, enabling an increase in pixel count by an order of magnitude. This increase allows a wider FOV and instantaneous velocity coverage. The upgrade provides gains in point source observation speed by a factor <2 and in mapping speed by a factor <3.5, enabled by the improved sensitivity and pixel count. This upgrade has been proposed to NASA in response to the 2018 SOFIA Next Generation Instrumentation call

Infrared view of the multiphase ISM in NGC 253 II. Modelling the ionised and neutral atomic gas

Context. Multi-wavelength studies of galaxies and galactic nuclei allow us to build a relatively more complete picture of the interstellar medium (ISM), especially in the dusty regions of starburst galaxies. An understanding of the physical processes in nearby galaxies can assist in the study of more distant sources at higher redshifts, which cannot be resolved. Aims. We aimed to use observations presented in the first part of this series of papers to model the physical conditions of the ISM in the nuclear region of NGC 253, in order to obtain primary parameters such as gas densities and metallicities. From the created model we further calculated secondary parameters such as gas masses of the different phases, and estimated the fraction of [C II] 158 um from the different phases, which allowed us to probe the nuclear star-formation rate. Methods. To compare theory with our observations we used MULTIGRIS, a probabilistic tool that determines probabilities for certain ISM parameters from a grid of Cloudy models together with a set of spectroscopic lines. Results. We find that the hypothetical active galactic nucleus within NGC 253 has only a minor impact compared to the starburst on the heating of the ISM as probed by the observed lines. We characterise the ISM and obtain parameters such as a solar metallicity, a mean density of ~230cm-3 , an ionisation parameter of log U = -3, and an age of the nuclear cluster of ~2 Myr. Furthermore, we estimate the masses of the ionised (3.8 x 10^6 M_sol ), neutral atomic (9.1 x 10^6 M_sol ), and molecular (2.0 x 10^8 M_sol ) gas phases as well as the dust mass (1.8 x 10^6 M_sol ) in the nucleus of NGC 253.Comment: Accepted for publication in A&A; 15 pages, 10 Figures, 6 Table