We present the fifth incarnation of the Mid-Infrared Array Camera (MIRAC-5) instrument which will use a new GeoSnap (3 – 13 microns) detector. Advances in adaptive optics (AO) systems and detectors are enabling ground based mid-infrared systems capable of high spatial resolution and deep contrast. As one of the only 3 – 13 micron cameras used in tandem with AO, MIRAC-5 will be complementary to the James Webb Space Telescope (JWST) and capable of characterizing gas giant exoplanets and imaging forming protoplanets (helping to characterize their circumplanetary disks). We describe key features of the MIRAC-5 GeoSnap detector, a long-wave Mercury-Cadmium-Telluride (MCT) array produced by Teledyne Imaging Sensors (TIS), including its high quantum efficiency (> 65%), large well-depth, and low noise. We summarize MIRAC-5’s important capabilities, including prospects for obtaining the first continuum mid-infrared measurements for several gas giants and the first 10.2-10.8 micron NH3 detection in the atmosphere of the warm companion GJ 504b (Teff ~ 550 K) within 8 hours of observing time. Finally, we describe plans for future upgrades to MIRAC-5 such as adding a coronagraph. MIRAC5 will be commissioned on the MMT utilizing the new MAPS AO system in late 2022 with plans to move to Magellan with the MagAO system in the future.

Coauthors/Endorsers: P. Abell (JSC), Michele T. Bannister, School of Physical and Chemical Sciences | Te Kura Matū, U. Canterbury, B. Barbee (GSFC), J. Barnes (U. Arizona), J.F. Bell III (ASU), L. Benner (JPL), B. Betts (Planetary Society), Maitrayee Bose (ASU), W. Bottke (SwRI), D. Britt (U. Central Florida), M. Brozović (JPL), M. Bruckner (U. Arizona), Michael W. Busch (SETI), S. Carey (IPAC/Caltech), J. Castillo-Rogez (JPL), J. Chesley (JPL), E. Christensen (U. Arizona), P. Chodas (JPL), D. Cotto-Figueroa (U. Puerto Rico at Humacao), M. Delbó (Observatoire de la Côte d'Azur), R. T. Daly (JHU/APL), J. Dotson (NASA-Ames), P. Eisenhardt (JPL), Y. R. Fernandez (U. Central Florida), Ronald A. Fevig (U. North Dakota), T. Grav (U. Arizona), S. Greenstreet (U. Washington), M. Gritsevich (Finnish Geospatial Research Institute), Heidi B. Hammel (AURA), A. Harris (DLR), W. Harris (U. Arizona), D. Hickson (U. Central Florida), Kynan Hughson (Georgia Institute of Technology), Željko Ivezić (U. Washington), Devanshu Jha (MVJCE, India), Lynne Jones (U. Washington), Mario Jurić (U. Washington), B. Kacar (U. Arizona), D. Lauretta (U. Arizona), Joseph Lazio (JPL), Rosaly M.C. Lopes (JPL), F. Marchis (SETI Institute), Sean E. Marshall (Arecibo/U. Central Florida), J. Masiero (JPL), D. Mathias (NASA-Ames), R. S. McMillan (U. Arizona), C. McMurtry (U. Rochester), P. Michel (U Côte d’Azur, Obs. Côte d’Azur, CNRS), S. Naidu (JPL), M. C. Nolan (U. Arizona), T. Okada (ISAS/JAXA), J. L. Pipher (U. Rochester), Carol Raymond (JPL), E. Rivera-Valentín (LPI/URSA), A. Rivkin (APL/Johns Hopkins University) C. A. Schambeau (U. Central Florida), D. Scheeres (U. Colorado), Jennifer Scully (JPL), S. Sonnett (PSI), T. Spahr (NEO Sciences), A. Stern (SwRI), T. Swindle (U. Arizona), P. Taylor (LPI/USRA), D. Takir (JSC), M. Telus (UC Santa Cruz), C. Thomas (NAU), F. C. F. Venditti (Arecibo/U. Central Florida), Anne K. Virkki (Arecibo/U. Central Florida), A. Wong (U. Arizona), E. L. Wright (UCLA)

We present a study of the kinematics and structure of the Cep OB3b cluster based on new spectra obtained with the Hectoschelle spectrograph on the MMT and data from Spitzer , Chandra , and Gaia . At a distance of 819 ± 16 pc, Cep OB3b is one of the closest examples of a young (∼3–5 Myr), large (∼3000 total members) cluster at the late stages of gas dispersal. The cluster is broken into two subclusters surrounded by a lower density halo. We fit the empirical density law of King to each subcluster to constrain their sizes and structure. The richer eastern subcluster has circular symmetry, a modest central density, and lacks molecular gas toward its core, suggesting it has undergone expansion due to gas dispersal. In contrast, the western subcluster deviates from circular symmetry, has a smaller core size, and contains significant molecular gas near its core, suggesting that it is in an earlier phase of gas dispersal. We present posterior probability distributions for the velocity dispersions from the Hectoschelle spectra. The east will continue to expand and likely form a bound cluster with ∼35% of stars remaining. The west is undergoing slower gas dispersal and will potentially form a bound cluster with ∼75% of stars remaining. If the halo dissipates, this will leave two independent clusters with ∼300 members; proper motions suggest that the two subcluster are not bound to each other.

The giant molecular cloud G216-2.5, also known as Maddalena’s cloud or the Maddalena-Thaddeus cloud, is distinguished by an unusual combination of high gas mass (1 − 6 × 10 M⊙), low kinetic temperatures (10 K), and the lack of bright far infrared emission. Although star formation has been detected in neighboring satellite clouds, little evidence for star formation has been found in the main body of this cloud. Using a combination of mid-infrared observations with the IRAC and MIPS instruments onboard the Spitzer space telescope, and near-IR images taken with the Flamingos camera on the KPNO 2.1-meter, we identify a population of 41 young stars with disks and 33 protostars in the center of the cloud. Most of the young stellar objects are coincident with a filamentary structure of dense gas detected in CS (2 → 1). These observations show that the main body of G216 is actively forming stars, although at a low stellar density comparable to that found in the Taurus cloud. Subject headings: stars:protostars, stars: pre-main sequence, ISM:molecular clouds Ritter Observatory, MS-113, University of Toledo, 2801 W. Bancroft St, Toledo, OH, 43560 (megeath@physics.utoledo.edu) Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721 Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation. European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany Based on observations made with ESO telescopes at the La Silla Observatory

ABSTRACT 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 ≥10 pc −2 , we find that 59% of the YSOs are in the largest cluster, the Orion Nebula 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 shows 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 ∼2 Myr in age. We find that 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 dynamical interactions in dense, clustered regions.

Collaboration between Exelis Geospatial Systems with University of Rochester and Rochester Institute of Technology aims to develop an active THz imaging focal plane array utilizing 0.35um CMOS MOSFET technique. An appropriate antenna is needed to couple incident THz radiation to the detector which is much smaller than the wavelength of interest. This paper simply summarizes our work on modeling the optical characteristics of bowtie antennae to optimize the design for detection of radiation centered on the atmospheric window at 215GHz. The simulations make use of the finite difference time domain method, calculating the transmission/absorption responses of the antenna-coupled detector.

The Folded-port InfraRed Echellette (FIRE) has recently been commissioned on the Magellan 6.5m Baade Telescope. This single object, near-infrared spectrometer simultaneously covers the 0.85-2.45 micron window in both cross-dispersed (R ~ 6000) or prism-dispersed (R ~ 250-350) modes. FIRE's compact configuration, high transmission optics and high quantum efficiency detector provides considerable sensitivity in the near-infrared, making it an ideal instrument for studies of cool stars and brown dwarfs. Here we present some of the first cool star science results with FIRE based on commissioning and science verification observations, including evidence of clouds in a planetary-mass brown dwarf, accretion and jet emission in the low-mass T Tauri star TWA 30B, radial velocities of T-type brown dwarfs, and near-infrared detection of a debris disk associated with the DAZ white dwarf GALEX 1931+01.

We identify protostars in Spitzer surveys of nine star-forming molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine photometry from 2MASS J, H, and Ks bands and Spitzer IRAC and MIPS 24 micron bands to create 1 - 24 micron spectral energy distributions (SEDs). Using protostars from the c2d survey with well-determined bolometric luminosities (Lbol), we derive a relationship between Lbol, L_MIR (integrated from 1 - 24 microns), and SED slope. Estimations of Lbol for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high mass star forming clouds peak near 1 Lsun and show a tail extending toward luminosities above 100 Lsun. The luminosity functions of the low mass star forming clouds do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 Lsun. Finally, we examine the luminosity functions as a function of the local surface density of YSOs. In the Orion molecular cloud, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity functions to those predicted by models and find that our observed luminosity functions are best matched by models which invoke competitive accretion, although we do not find strong agreement of the high mass star forming clouds with any of the models.

The giant molecular cloud G216-2.5, also known as Maddalena's cloud or the Maddalena–Thaddeus cloud, is distinguished by an unusual combination of high gas mass (1–6 × 105M☉), low kinetic temperatures (10 K), and the lack of bright far-IR emission. Although star formation has been detected in neighboring satellite clouds, little evidence for star formation has been found in the main body of this cloud. Using a combination of mid-IR observations with the IRAC and Multiband Imaging Photometer for Spitzer instruments onboard the Spitzer Space Telescope, and near-IR images taken with the Flamingos camera on the KPNO 2.1 m telescope, we identify a population of 41 young stars with disks and 33 protostars in the center of the cloud. Most of the young stellar objects are coincident with a filamentary structure of dense gas detected in CS (2 → 1). These observations show that the main body of G216 is actively forming stars, although at a low stellar density comparable to that found in the Taurus cloud.

We present a uniform mid-infrared imaging and photometric survey of 36 young, nearby, star-forming clusters and groups using {\it Spitzer} IRAC and MIPS. We have confidently identified and classified 2548 young stellar objects using recently established mid-infrared color-based methods. We have devised and applied a new algorithm for the isolation of local surface density enhancements from point source distributions, enabling us to extract the overdense cores of the observed star forming regions for further analysis. We have compiled several basic structural measurements of these cluster cores from the data, such as mean surface densities of sources, cluster core radii, and aspect ratios, in order to characterize the ranges for these quantities. We find that a typical cluster core is 0.39 pc in radius, has 26 members with infrared excess in a ratio of Class II to Class I sources of 3.7, is embedded in a $A_K$=0.8 mag cloud clump, and has a surface density of 60 pc$^{-2}$. We examine the nearest neighbor distances among the YSOs in several ways, demonstrating similarity in the spacings between Class II and Class I sources but large member clusters appear more dense than smaller clusters. We demonstrate that near-uniform source spacings in cluster cores are common, suggesting that simple Jeans fragmentation of parsec-scale cloud clumps may be the dominant process governing star formation in nearby clusters and groups. Finally, we compare our results to other similar surveys in the literature and discuss potential biases in the data to guide further interpretation.

Forty new low mass members with spectral types ranging from M4-M9 have been confirmed in the Orion Molecular Cloud 2/3 region. Through deep, I, z', J, H, K photometry of a 20' x 20' field in OMC 2/3, we selected brown dwarf candidates for follow-up spectroscopy. Low resolution far-red and near-infrared spectra were obtained for the candidates, and 19 young brown dwarfs in the OMC 2/3 region are confirmed. They exhibit spectral types of M6.5-M9, corresponding to approximate masses of 0.075-0.015 M_solar using the evolutionary models of Baraffe et al. (1998). At least one of these bona fide young brown dwarfs has strong Halpha emission, indicating that it is actively accreting. In addition, we confirm 21 new low mass members with spectral types of M4-M6, corresponding to approximate masses of 0.35-0.10 M_solar in OMC 2/3. By comparing pre-main sequence tracks to the positions of the members in the H-R diagram, we find that most of the brown dwarfs are less than 1 Myr, but find a number of low mass stars with inferred ages greater than 3 Myr. The discrepancy in the stellar and substellar ages is due to our selection of only low luminosity sources; however, the presence of such objects implies the presence of an age spread in the OMC 2/3 region. We discuss possible reasons for this apparent age spread.