Joseph D. Adams

Mass producing an efficient NIR spectrograph

Four institutions are collaborating to design and build three near identical R ~2700 cross-dispersed near-infrared spectrographs for use on various 5-10 meter telescopes. The instrument design addresses the common observatory need for efficient, reliable near-infrared spectrographs through such features as broad wavelength coverage across 6 simultaneous orders (0.8 - 2.4 microns) in echelle format, real-time slit viewing through separate optics and detector, and minimal moving parts. Lastly, the collaborators are saving money and increasing the likelihood of success through economies of scale and sharing intellectual capital.

FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: THE FORCAST MID-INFRARED CAMERA

The Stratospheric Observatory For Infrared Astronomy (SOFIA) completed its first light flight in May of 2010 using the facility mid-infrared instrument FORCAST. Since then, FORCAST has successfully completed 13 science flights on SOFIA. In this Letter, we describe the design, operation, and performance of FORCAST as it relates to the initial three Short Science flights. FORCAST was able to achieve near-diffraction-limited images for λ > 30 μm allowing unique science results from the start with SOFIA. We also describe ongoing and future modifications that will improve overall capabilities and performance of FORCAST.

The performance of TripleSpec at Palomar

We report the performance of Triplespec from commissioning observations on the 200-inch Hale Telescope at Palomar Observatory. Triplespec is one of a set of three near-infrared, cross-dispersed spectrographs covering wavelengths from 1 - 2.4 microns simultaneously at a resolution of ~2700. At Palomar, Triplespec uses a 1×30 arcsecond slit. Triplespec will be used for a variety of scientific observations, including moderate to high redshift galaxies, star formation, and low mass stars and brown dwarfs. When used in conjunction with an externally dispersed interferometer, Triplespec will also detect and characterize extrasolar planets.

The size and albedo of Rosetta fly-by target 21 Lutetia from new IRTF measurements and thermal modeling

Recent spectroscopic observations indicate that the M-type asteroid 21 Lutetia has a primitive, carbonaceous-chondrite-like (C-type) surface composition for which a low geometric albedo would be expected; this is incompatible with the IRAS albedo of 0.221+/- 0.020. From new thermal-infrared spectrophotometric measurements and detailed thermophysical modeling we infer that Lutetia has a diameter of 98.3 +/- 5.9 km and a geometric albedo of 0.208 +/- 0.025, in excellent agreement with the IRAS value. We can thus rule out a low albedo typical of a C-type taxonomic classification. Furthermore, we find that Lutetias thermal properties are well within the range expected for large asteroids; we find no evidence for unusually high thermal inertia.

A SPITZER VIEW OF STAR FORMATION IN THE CYGNUS X NORTH COMPLEX

Original article can be found at: http://iopscience.iop.org/0004-637X Copyright American Astronomical Society. [Full text of this article is not available in the UHRA]

Mid-Infrared Emission at Photodissociation Regions in the Orion Nebula

The mid-infrared emission from a photodissociation region (PDR) viewed edge-on in the Orion Nebula is examined through 8.7-20.6 ?m images and 8-13 ?m spectra. The polycyclic aromatic hydrocarbon (PAH) emission is located between the edges of H II regions and layers of [C I] emission, agreeing with PDR theory. Using a simple model, the spatial variations in the emission from PAHs detected at 8.6, 11.2, and 12.7 ?m are demonstrated to be directly proportional to the material column density and the intensity of the UV field. For a homogeneous, neutral cloud illuminated by a bright OB star, PDR theory predicts that the ultraviolet (UV) radiation is attenuated exponentially (e). The predicted UV attenuation is confirmed by observations of broad PAH emission features found at 8.6, 11.2, and 12.7 ?m. The PAH emission is found in cool regions having greater optical depths relative to regions where mid-infrared emission from ionized gas is observed. Through modeling we determine a gas density of 9.7 ? 104 cm-3. On large and small size scales, the relative strengths of the 8.6, 11.2, and 12.7 ?m PAH features at the bar of the Orion Nebula indicate that there is not a simple transition from ionized to neutral PAHs across the PDR.

FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: 6-37 μm IMAGING OF ORION BN/KL

The BN/KL region of the Orion Nebula is the nearest region of high mass star formation in our galaxy. As such, it has been the subject of intense investigation at a variety of wavelengths, which have revealed it to be brightest in the infrared to sub-mm wavelength regime. Using the newly commissioned SOFIA airborne telescope and its 5-40 micron camera FORCAST, images of the entire BN/KL complex have been acquired. The 31.5 and 37.1 micron images represent the highest resolution observations ( 31.5 microns, and that this distinction goes instead to the source IRc4. It was determined from these images and derived dust color temperature maps that IRc4 is also likely to be self-luminous. A new source of emission has also been identified at wavelengths >31.5 microns that coincides with the northeastern outflow lobe from the protostellar disk associated with radio source I.

On the Nature of the Deeply Embedded Protostar OMC-2 FIR 4

We use mid-infrared to submillimeter data from the Spitzer, Herschel, and Atacama Pathfinder Experiment telescopes to study the bright submillimeter source OMC-2 FIR 4. We find a point source at 8, 24, and 70 μm, and a compact, but extended source at 160, 350, and 870 μm. The peak of the emission from 8 to 70 μm, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the latter represents the large molecular core the protostar is embedded within. We determine that the protostar has a bolometric luminosity of 37 L☉, although including more extended emission surrounding the point source raises this value to 86 L☉. Radiative transfer models of the protostellar system fit the observed spectral energy distribution well and yield a total luminosity of most likely less than 100 L☉. Our models suggest that the bolometric luminosity of the protostar could be as low as 12-14 L☉, while the luminosity of the colder (~20 K) extended core could be around 100 L☉, with a mass of about 27 M☉. Our derived luminosities for the protostar OMC-2 FIR 4 are in direct contradiction with previous claims of a total luminosity of 1000 L☉. Furthermore, we find evidence from far-infrared molecular spectra and 3.6 cm emission that FIR 4 drives an outflow. The final stellar mass the protostar will ultimately achieve is uncertain due to its association with the large reservoir of mass found in the cold core.

DIVERSE PROTOSTELLAR EVOLUTIONARY STATES IN THE YOUNG CLUSTER AFGL961

We present arcsecond resolution mid-infrared and millimeter observations of the center of the young stellar cluster AFGL961 in the Rosette molecular cloud. Within 0.2 pc of each other, we find an early B star embedded in a dense core, a neighboring star of similar luminosity with no millimeter counterpart, a protostar that has cleared out a cavity in the circumcluster envelope, and two massive, dense cores with no infrared counterparts. An outflow emanates from one of these cores, indicating a deeply embedded protostar, but the other is starless, bound, and appears to be collapsing. The diversity of states implies either that protostellar evolution is faster in clusters than in isolation or that clusters form via quasi-static rather than dynamic collapse. The existence of a pre-stellar core at the cluster center shows that some star formation continues after and in close proximity to massive, ionizing stars.

Spitzer, Near-Infrared, and Submillimeter Imaging of the Relatively Sparse Young Cluster, Lynds 988e

We present Spitzer images of the relatively sparse, low-luminosity young cluster L988e, as well as complementary near-infrared (NIR) and submillimeter images of the region. The cluster is asymmetric, with the western region of the cluster embedded within the molecular cloud, and the slightly less dense eastern region to the east of, and on the edge of, the molecular cloud. With these data, as well as with extant Hα data of stars primarily found in the eastern region of the cluster, and a molecular 13CO gas emission map of the entire region, we investigate the distribution of forming young stars with respect to the cloud material, concentrating particularly on the differences and similarities between the exposed and embedded regions of the cluster. We also compare star formation in this region to that in denser, more luminous and more massive clusters already investigated in our comprehensive multiwavelength study of young clusters within 1 kpc of the Sun.