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We present an independent estimate of the interstellar extinction law for the Spitzer IRAC bands as well as a first attempt at extending the law to the 24micron MIPS band. The source data for these measurements are observations of five nearby star-forming regions: the Orion A cloud, NGC 2068/71, NGC 2024/23, Serpens and Ophiuchus. Color excess ratios E(H-Ks)/E(Ks-[lambda]) were measured for stars without infrared excess dust emission from circumstellar disks/envelopes. For four of these five regions, the extinction laws are similar at all wavelengths and differ systematically from a previous determination of the extinction law, which was dominated by the diffuse ISM, derived for the IRAC bands. This difference could be due to the difference in the dust properties of the dense molecular clouds observed here and those of the diffuse ISM. The extinction law at longer wavelengths toward the Ophiuchus region lies between that to the other four regions studied here and that for the ISM. In addition, we extended our extinction law determination to 24micron for Serpens and NGC 2068/71 using Spitzer MIPS data. We compare these results against several ISO extinction law determinations, although in each case there are assumptions which make absolute comparison uncertain. However, our work confirms a relatively flatter extinction curve from 4 - 8micron than the previously assumed standard, as noted by all of these recent studies. The extinction law at 24micron is consistent with previous measurements and models, although there are relatively large uncertainties., Comment: accepted to ApJ. 37 pages, 10 figures

We analyze the spatial distribution of dusty young stellar objects (YSOs) identified in the Spitzer Survey of the Orion Molecular clouds, augmenting these data with Chandra X-ray observations to correct for incompleteness in dense clustered regions. We also devise a scheme to correct for spatially varying incompleteness when X-ray data are not available. The local surface densities of the YSOs range from 1 pc$^{-2}$ to over 10,000 pc$^{-2}$, with protostars tending to be in higher density regions. This range of densities is similar to other surveyed molecular clouds with clusters, but broader than clouds without clusters. By identifying clusters and groups as continuous regions with surface densities $\ge10$ pc$^{-2}$, we find that 59% of the YSOs are in the largest cluster, the Orion Nebular Cluster (ONC), while 13% of the YSOs are found in a distributed population. A lower fraction of protostars in the distributed population is evidence that it is somewhat older than the groups and clusters. An examination of the structural properties of the clusters and groups show that the peak surface densities of the clusters increase approximately linearly with the number of members. Furthermore, all clusters with more than 70 members exhibit asymmetric and/or highly elongated structures. The ONC becomes azimuthally symmetric in the inner 0.1 pc, suggesting that the cluster is only $\sim 2$ Myr in age. We find the star formation efficiency (SFE) of the Orion B cloud is unusually low, and that the SFEs of individual groups and clusters are an order of magnitude higher than those of the clouds. Finally, we discuss the relationship between the young low mass stars in the Orion clouds and the Orion OB 1 association, and we determine upper limits to the fraction of disks that may be affected by UV radiation from OB stars or by dynamical interactions in dense, clustered regions., Comment: Accepted to AJ. Higher resolution and two column version of paper as well as photometry data available at http://astro1.physics.utoledo.edu/~megeath/Orion/The_Spitzer_Orion_Survey.html

A lamellar grating has been developed to be used for very far ir observations on the Gerard P. Kuiper Airborne Observatory. The design characteristics and performance during laboratory testing and initial observations of Jupiter at wavelengths between 50 microm and 500 microm are presented.

A cryogenic paint which remains absorptive throughout the infrared has been developed. The paint exhibits excellent surface stability at liquid helium temperature and is resistant to abrasion and flaking. Measurements in a specially constructed cryogenic integrating sphere indicate that the paint is ~92-100% absorptive in the 70-130-micro range. Additional broadband measurements at 60 micro-130 micro, 18 micro-25micro, and 400 micro-1 mm indicate that the paint is ~95% absorptive.

We have compared directly the performance of a Pb1−xSnxTe(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb1−xSnxTe(In) photodetector has current responsivity SI several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with SI∼103 A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb1−xSnxTe(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions.

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC., Comment: 7 pages, 3 figures. Accepted for publication in the ApJS. A higher resolution version is at http://cfa-www.harvard.edu/irac/publications

Spatial studies of the emission line regions in planetary nebulae (PN) can provide insight into the physical and chemical environments across the nebulae. In a collaborative effort by the coauthors, a K-band Fabry-Perot etalon has been coupled with an advanced 256 × 256 InSb focal plane array at the Wyoming Infrared Observatory 2.3m telescope. This system permits us to obtain spatially resolved, 0.24″/pixel, moderate spectral resolution (R ≈ 800), flux-density IR emission line images of astronomical sources. We obtained continuum-subtracted images of Br γ, HeI 2.06 μm, the 2-μm UIR features, and the 3.3 μm PAH dust feature in the PN NGC 6572, NGC 7027, and NGC 7662. One objective was to determine the spatial morphology of two unidentified emission lines, UIR1−2.199 μm, and UIR2−2.287 μm (Geballe et al. 1991). These UIR lines appear in the spectra of many PN (Hora et al. 1997) and in the Orion Nebula (Luhman & Rieke 1996). Geballe et al. suggested that the UIR lines are most likely forbidden transitions and showed that the parent ion ionization potential is ≈ 30–40 eV, while the ionization potential for the ions themselves is 40–60 eV. Here we directly compare the distribution of the UIR emitters to that of the gas (H+,He+) and dust (PAHs).

High spatial spectral resolution IR images of the Galactic center in the Br-gamma recombination line of hydrogen were taken. A coherent filament of gas extending from north of IRS 1, curving around IRS 16/Sgr A complex, and continuing to the southwest, is seen. Nine stellar sources have associated Br-gamma emission. The total Br-gamma line flux in the filament is approximately 3 x 10 exp -15 W/sq m. The distribution and kinematics of the northern arm suggest orbital motion; the observations are accordingly fit with elliptical orbits in the field of a central point of mass.

Limb darkening on earth night side observed by Aerobee rocket, with explanation based on atmospheric opacity in water vapor and carbon dioxide bands

Images of the central parsec of the galaxy have been obtained in the Brα emission line of hydrogen. The images are, for the most part, very similar to 5 and 15 GHz radio continuum images of this region. Alignment of the Brα with the radio images gives an improved position of the Sgr A* radio point source with respect to the infrared sources: 5.50‘ S and 0.15‘ W of IRS 7, a position remarkably devoid of compact objects in the near infrared. This position rules out identification of Sgr A* with IRS 16 Centre or IRS 16NW. A number of compact Brα sources with no radio counter‐parts are seen. There is a string of four sources just north of Sgr A*, which itself is located in a Brα void. An isolated Brα source was also seen ≊10‘ SW or Sgr A*. These Brα sources may arise in very dense regions (optically thick in the radio), may be very cold, or may result from collosional excitation. They may also indicate the presence of local exciting sources in the central parsec.

1.9 to 4.1‐μm spectra of the compact infrared sources IRS 3, 4, and 19 are presented. IRS 3 lacks a strong ice absorption to accompany its enhanced silicate absorption. IRS 4 shows a 3.3‐μm emmision feature thought to arise from interfaces begween molecular and ionized gas. IRS 19 shows an extremely deep 3.1‐μm absorption superposed on the steam band that originates in a stellar atmosphere.

The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg2 in the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes ≈370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 σ limits of 6.4, 8.8, 51, and 50 μJy at 3.6, 4.5, 5.8, and 8 μm, respectively, including some with unusual spectral energy distributions.

Infrared images of the BN-KL region in Orion obtained with the Univ. of Rochester IR Array Camera on the Mees 0.6-m (2.5“/pixel) and the Kitt Peak 1.3-m telescopes (1”/pixel) are presented. These images demonstrate the utility of small telescopes for infrared studies of star formation regions.

The region S106 = G 76.4 — 0.6 has been photographed in the 8000Å region with the Carnegie image converter attached to the 0.6m telescope at the Mees Observatory. This was done in connection with a larger program designed to assemble radio, infrared, and optical data on compact HII regions.S106 has angular dimensions of 1’ by 3’ and has relatively high surface brightness. Its kinematic distance based on H109a observations (Reinfenstein, et al. 1970) is 2.3 kpc ± 3.0.Several bright maxima are observed within the nebula at wavelengths of 12.6/x and 2.7 GHz. These are believed to be the result of thermal radiation from hot dust and free-free emission from ionized gas, respectively. At the nominal distance their linear sizes are of the order of 0.2 pc and they may be similar to the “cocoon” type objects discussed by various authors.

On presente l'interferometrie speckle IR de AFGL 915, la source centrale associee a HD 44179 ainsi que la polarimetrie IR de la source ponctuelle et de la nebuleuse qui l'entoure. Ces observations servent a preciser les modeles de cet objet enigmatique

Spatial, photometric, and spectrophotometric observations of the compact H ii region G29.9--0.0 are reported. The photometric observations indicate that the infared object agrees in position and size with the radio source. Spectrophotometry from 8--13 $mu$ shows a broad absorption feature, as well as fine-structure emission lines of Ar$sup ++$ and Ne$sup +$. Model fits to the spectrum of G29.9--0.0 indicate that three is strong absorption throughout the 8- 13 $mu$ spectral region. The photometry indiates that dust competes with the gas for absorbing the ionizing stellar continuum, while there is evidence for a depletion of dust within the ionized region. A comparison of 2.2 $mu$-10 $mu$ extinction to the source indicates that A/subv//tau$sub 9$.$sub 75$/sub mu/>6 mag.