Justin Schoenwald

PHARO: A Near‐Infrared Camera for the Palomar Adaptive Optics System

We describe Cornells near-infrared camera system PHARO (Palomar High Angular Resolution Observer) built for use with the JPL Palomar Adaptive Optics System on the 5 m Hale telescope. PHARO uses a HgCdTe HAWAII detector for observations between 1 and 2.5 mm wavelength. An all-reflecting 1024 # 1024

The infrared spectrograph on the Spitzer Space Telescope

The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope. The IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38 μm with spectral resolutions, R~90 and 650, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the pre-launch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data reduction pipeline has been developed at the Spitzer Science Center.

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.

SpectroCam-10: a 10-μm spectrograph/camera for the Hale Telescope

SpectroCam-10 is a 10 micrometers spectrograph and camera built at Cornell University as a facility instrument for the 200 inch Hale telescope. The instrument is optimized for operation from (lambda) equals 8 to 13 micrometers in three modes: a medium-resolution spectrography (R equals (lambda) /(Delta) (lambda) approximately equals 2000), a low-resolution spectrography (R approximately equals 100), and a camera with diffraction limited (0.5 arcsec) spatial resolution. An optical flat and two reflection gratings mounted on a cryogenic rotating mechanism allow rapid switching between modes. The detector is a Rockwell 128 X 128 Si:As Back Illuminated Blocked Impurity Band array. We discuss the design and operation of the instrument, and present some scientific results from our early observing runs at Palomar.

The Second-generation z (Redshift) and Early Universe Spectrometer. I. First-light Observation of a Highly Lensed Local-ulirg Analog at High-z

We recently commissioned our new spectrometer, the second-generation z(Redshift) and Early Universe Spectrometer (ZEUS-2) on the Atacama Pathfinder Experiment telescope. ZEUS-2 is a submillimeter grating spectrometer optimized for detecting the faint and broad lines from distant galaxies that are redshifted into the telluric windows from 200 to 850 μm. It uses a focal plane array of transition-edge sensed bolometers, the first use of these arrays for astrophysical spectroscopy. ZEUS-2 promises to be an important tool for studying galaxies in the years to come because of its synergy with Atacama Large Millimeter Array and its capabilities in the short submillimeter windows that are unique in the post-Herschel era. Here, we report on our first detection of the [C II] 158 μm line with ZEUS-2. We detect the line at z ~ 1.8 from H-ATLAS J091043.1–000322 with a line flux of (6.44 ± 0.42) × 10^(–18) W m^(–2). Combined with its far-IR luminosity and a new Herschel-PACS detection of the [O I] 63 μm line, we model the line emission as coming from a photo-dissociation region with far-ultraviolet radiation field, G ~ 2 × 10^4 G_0, gas density, n ~ 1 × 10^3 cm^(–3) and size between ~0.4 and 1 kpc. On the basis of this model, we conclude that H-ATLAS J091043.1–000322 is a high-redshift analog of a local ultra-luminous IR galaxy; i.e., it is likely the site of a compact starburst caused by a major merger. Further identification of these merging systems is important for constraining galaxy formation and evolution models.

The Infrared spectrograph on the Spitzer Space Telescope

The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope .T he IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38 � m with spectral resolutions, R ¼ k=� k � 90 and 600, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the prelaunch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data-reduction pipeline has been developed at the Spitzer Science Center. Subject headingg infrared: general — instrumentation: spectrographs — space vehicles: instruments

SOFIA/FORCAST AND SPITZER/IRAC IMAGING OF THE ULTRACOMPACT H II REGION W3(OH) AND ASSOCIATED PROTOSTARS IN W3

We present infrared observations of the ultracompact H II region W3(OH) made by the FORCAST instrument aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) and by the Spitzer/Infrared Array Camera. We contribute new wavelength data to the spectral energy distribution (SED), which constrains the optical depth, grain size distribution, and temperature gradient of the dusty shell surrounding the H II region. We model the dust component as a spherical shell containing an inner cavity with radius ~600 AU, irradiated by a central star of type O9 and temperature ~31, 000 K. The total luminosity of this system is 7.1 ? 104 L ?. An observed excess of 2.2-4.5 ?m emission in the SED can be explained by our viewing a cavity opening or clumpiness in the shell structure whereby radiation from the warm interior of the shell can escape. We claim to detect the nearby water maser source W3 (H2O) at 31.4 and 37.1 ?m using beam deconvolution of the FORCAST images. We constrain the flux densities of this object at 19.7-37.1 ?m. Additionally, we present in situ observations of four young stellar and protostellar objects in the SOFIA field, presumably associated with the W3 molecular cloud. Results from the model SED fitting tool of Robitaille et?al. suggest that two objects (2MASS J02270352+6152357 and 2MASS J02270824+6152281) are intermediate-luminosity (~236-432 L ?) protostars; one object (2MASS J02270887+6152344) is either a high-mass protostar with luminosity 3 ? 103 L ? or a less massive young star with a substantial circumstellar disk but depleted envelope; and the other (2MASS J02270743+6152281) is an intermediate-luminosity (~768 L ?) protostar nearing the end of its envelope accretion phase or a young star surrounded by a circumstellar disk with no appreciable circumstellar envelope.

PHARO (Palomar high-angular-resolution observer): a dedicated NIR camera for the Palomar adaptive optics system

We describe Corneirs NIR camera system for the Hale 200” telescope adaptive optics system at Palomar Observatory. The instrument is under construction at this time, and we expect first light at the telescope in December 1997. Here we summarize the camera’s design as well as its expected performance.

Evaluation of Si:As and Si:Sb blocked-impurity-band detectors for SIRTF and WIRE

Cryogenic telescopes in space offer dramatic reduction in thermal IR background flux. Outstanding performance in the areas of detector dark current, read noise, and radiation hardness are required to take full advantage of the sensitivity improvements possible with such facilities, especially in very low flux (2 to 100 photons/pixel/sec) applications such as the Infrared Spectrograph on SIRTF. We present our testing methods and our results on Si:As and Si:Sb block impurity band (BIB) detectors produced by Rockwell International for our SIRTF and WIRE applications. Remarkable recent results are the reduction of the multiple-sampling read noise to 30 electrons, reduction of dark current to 10 e-/s for Si:As and 40 e-/s for Si:Sb, the use of an antireflective coating to improve the detective quantum efficiency for Si:As, extension of the useful wavelength range of Si:Sb to 40 microns, and confirmation that lab data on a 50 s time scale can be extrapolated to integration times at least 10 times longer.

SCORE 1+: enhancing a unique mid-infrared spectrograph

SCORE is a cross-dispersed echelle spectrograph, built as a prototype for the Short-High module of SIRTFs IRS instrument. It operates over the 7.5-15 micrometers N-band atmospheric window, and has ben used on Palomars Hale telescope several times since November, 1996. Since the initial run, a number of improvements have ben undertaken or are in the process being undertaken which enhance SCOREs performance and simplify its operation. One such addition, now completed, is a second detector array which serves as a slit-viewer with 12 inch diameter field of view around the slit. This viewer allows easy acquisition and guidance for sources with dim or absent optical counterparts, and accurately registers the position of the slit on the source with the recorded spectrum. Software written in the IDL environment optimizes the extraction of spectra form SCOREs mid-IR crossed-echelle data. The echelle, while providing the advantage of increased pixel utilization, introduces several difficulties, including curved orders, order cross- talk, and differentially slanted lines. These and other instrumental artifacts must be removed to achieve the highest spectral signal-to-noise. The pixel efficiency will be further increased by the use of a grism predisperser. The grism will provide approximately even spacing between orders of the echelle, in contrast with the decreasing spacing towards shorter wavelength orders generated by the current grating. SCORE is already one of the most powerful short- slit spectrographs operating in this wavelength band, and, with the implementation of these improvements, will deliver even greater capability.