Past Events in 2017

X-ray and mid-infrared (MIR) wavelength observations are crucial for studies of active galactic nuclei (AGN) because X-rays trace the intrinsic power of AGN and the MIR traces the warm (T~200-300 K) thermal dust (called ``torus'') surrounding the central engine. However, the geometrical structure of the torus is not well understood due to its compact size (r<10 pc).  In this talk, I will first introduce our recently published infrared catalog of Swift/BAT hard X-ray 70 month AGN catalog.

We describe the current status of the HAWC+ instrument for SOFIA after recent commissioning and first science flights. HAWC+ is a multi-band far-infrared imager featuring three 32x40 detector arrays, with two of the arrays in an optimum polarimeter configuration, and a set of half-wave-plate polarization modulators. The detectors use transition-edge sensors in a BUG architecture from Goddard, hybridized with SQUID multiplexers from NIST. HAWC+ observes in four continuum bands from 53 to 216 microns, offering angular resolution as fine as 5" (FWHM) when operated on the SOFIA telescope.

AGN unification and the clumpiness of the central obscurer ("torus") are mostly accepted, and both orientation and clumpiness designate an AGN as type-1 or type-2. Observations continue to add second-order complications, though. Small type-1 / type-2 samples have been compared through SED fitting, IR interferometry, and X-ray monitoring. It is, however, especially difficult to obtain large samples of type-2 AGN, since they are both dimmer and redder. To understand better the nuclear obscurer, we attack the problem at multiple wavelengths.

The HI and CO components of the interstellar medium (ISM) are often used to derive the dynamical mass of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 μm line of atomic carbon ([C II]) may be the only way to derive this. As the distribution and kinematics of the ISM tracer affects the determination of the dynamical mass, it is important to quantify the relative distributions of HI, CO, and [C II].

I will present recent results from SOFIA/FORCAST imaging of massive young stellar objects (YSOs) in three star-forming HII regions of the Large Magellanic Cloud. We use photometry at 25.3–37.1 μm to constrain model fits to near/mid-infrared SEDs and determine luminosities, ages, and dust content of the embedded YSOs and their local environments. By placing observed sources on mid-infrared color–magnitude and color–color diagrams, we analyze their dust properties and consider their evolutionary status.

Polycyclic aromatic hydrocarbons, or PAHs, have proven to be the best candidate to explain the strong infrared emission features that appear wherever a hot radiation field impinges on a dust cloud with carbon-rich grains, from nearby planetary nebulae to high-redshift starburst galaxies.  We see the PAHs as the dust is being destroyed, but what does the carbon-rich material look like before that happens?

An extreme environment for star formation, the center of our Galaxy is observed to have many properties in common with those of high-redshift galaxies. As our best local analog for these sources, it provides a unique opportunity to probe detailed gas properties and their impact on star formation at a spatial resolution that is unobtainable at the high redshifts of the peak of star formation and galaxy assembly.

Effective stray light control is a key requirement for wide dynamic range performance of scientific optical systems, particularly in the infrared. Unwanted radiation can deteriorate detection measurement by contributing high background flux/noise as well as stochastic (such as telescope pointing dependent) variations that degrade instrument calibration performance. Designs for stray light control solutions cover a wide range of technologies and approaches: baffles and structures, specialized low and high emissivity coatings and coatings maintenance.

The formation of massive clusters is governed by feedback on multiple scales, from the parsec-scale destructive feedback of HII regions and supernovae to the much smaller range of possibly productive thermal feedback. I will present ALMA and JVLA observations of a high-mass star-forming region in which dozens of O-stars have already formed, yet the gas mass is still much larger than the stellar mass. The most massive protostellar 'cores' consist of surprisingly large volumes of warm (>100 K) gas, yet dense gas around other high-mass stars appears untouched by their radiation.

Nuclear Astrophysics is a field that is concerned with the nuclear physics associated with the synthesis of nuclei and the energy generation processes in quiescent and explosive stellar burning environments. This presentation will present a number of these scenarios that contribute to the origin of the elemental abundance distribution as observed today. I will discuss the experimental needs for investigating key reactions in different phases of quiescent stellar burning.

There is a deep connection between star formation and AGN activity which profoundly impacts the mass assembly history of galaxies. The nature of the connection however remains controversial, due to, for example, evolution in the AGN and starburst duty cycles, and the obscuring effect of dust.

Meteorites have long been considered as reflections of the compositional diversity of main belt asteroids and consequently they have been used to decipher their origin, formation, and evolution. However, while some meteorites are known to sample the surfaces of metallic, rocky and hydrated asteroids (about one-third of the mass of the belt), the low-density icy asteroids (C-, P-, and D-types), representing the rest of the main belt, appear to be unsampled in our meteorite collections.

Nearby galaxies are some of the best laboratories to understand the physical processes that drive galaxy evolution. I will present spatially-resolved far-infrared spectroscopic observations in these systems obtained with Herschel (KINGFISH, Beyond the Peak, and HS3MC) and followup programs from SOFIA. I will discuss the use of several FIR indicators as measures of star formation rate, volume density, column density, and ISM pressure.

While theoretical dust condensation models and observations of dusty high redshift galaxies imply that core-collapse supernova (SN) explosions should efficiently form dust, large quantities of dust have so far only been directly observed in SN 1987A. One of the main challenges in characterizing dust masses and compositions in supernova remnants (SNRs) is the inability to disentangle the emission from SN-formed dust from other ambient material. SNRs that contain pulsar wind nebulae (PWNe) can serve as powerful probes of the SN ejecta and dust that would otherwise be unobservable.

I will discuss the story of how the very red stellar object, IRC+10216, was discovered first on the 2.2 micron 61 inch all sky survey at Mount Wilson in about 1964.  Four years later the source was determined to be extremely red and the brightest object in the sky at 5 microns outside the solar system on the old 60 inch optical telescope also at Mount Wilson.  Follow up work by several groups showed that it was an extreme Carbon star at a distance of 200 pc.  In 1990 Mike Jura introduced me to Harry Kroto who had just discovered C₆₀ with the Rice group lead by Richard Smalley.  T

Community input is sought for far-infrared instrument needs across multiple platforms (balloons, SOFIA, sub-orbital, FIR probes). Bring your knowledge of what science gaps we still have in the far-IR and how we can shape our existing and future platforms to get these measurements. We hope to see you there.

More information here.

The Origins Space Telescope (OST) is one of the concepts under study for the 2020 Decadal.  OST is a large (8-15 meter diameter) actively cooled (4 K structure) telescope equipped with a multiple-instrument complement that will answer questions aligned with four large science themes: (1) Tracing the Signatures of Life and the Ingredients of Habitable Worlds, (2) Unveiling the Growth of Black Holes and Galaxies over Cosmic Time, (3) Charting the Rise of Metals, Dust, and the First Galaxies, and (4) Characterizing Small Bodies in the Solar System.

Massive stars are important throughout astrophysics, but their formation mechanism remains the subject of much debate. SOFIA is uniquely capable of probing the highly extincted regions in which massive star formation is taking place. Following our study of G35.20-0.74 with SOFIA-FORCAST in Basic Science (Zhang et al. 2013), we started the SOMA Survey with the goal of eventually observing about 50 high- and intermediate-mass protostars across a range of Galactic environments and evolutionary stages. So far, just over 20 sources have been observed.

The central engine of an active galactic nucleus (AGN) is accretion onto a supermassive black hole. The surrounding dust and gas shape our view of the underlying energetic processes, often obscuring them, figuratively and literally. I will present a variety of recent results based largely on infrared observations of nearby AGN that clumpy or inhomogeneous surroundings explain well, while leaving open a number of specific questions about the role of AGN in feedback that governs galactic-scale evolution.

We report the discovery of water maser emission at frequencies above 1THz. Using the GREAT instrument on SOFIA, we have detected emission in the 1.296411 THz 8(27)-7(34) transition of water toward three oxygen-rich evolved stars: W Hya, U Her, and VY CMa. An upper limit on the 1.296 THz line flux was obtained toward R Aql. Near-simultaneous observations of the 22.23508 GHz 6(16)-5(23) water maser transition were carried out towards all four sources, providing quantitative determinations of the 22GHz / 1.296 THz photon luminosity ratio in the range 0.012 to 0.138.