First Science Observations With Sofia/Forcast: The Forcast Mid-Infrared Camera

Herter, T.; Adams, Joseph D.; Buizer, James M. De; Gull, G. E.; Schoenwald, Justin; Henderson, C.; Keller, L. D.; Nikola, Thomas; Stacey, G. J.; Vacca, William D.

doi:10.1088/2041-8205/749/2/l18

Cited by 107 publications

(87 citation statements)

References 7 publications

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“…Imaging and spectroscopic observations taken at sufficient spatial resolution will be needed to map secular changes in dust opacities and the distribution of the coolest dust, which dominates the dust masses. Such observations can be partly accomplished with the Faint Object Infrared Camera (FORCAST; Herter et al 2012) and the Far Infrared Field-Imaging Line Spectrometer (FIFI-LS; Colditz et al 2012) for the SOFIA Telescope. Additional mapping of the C + 1900.54 GHz line with the SOFIA German REceiver for Astronomy at Terahertz Frequencies (GREAT; Güsten et al 2000) may also elucidate the nature of the absorption and emission toward and around the Homunculus.…”

Section: Future Workmentioning

confidence: 99%

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Morris

Gull

Hillier

et al. 2017

ApJ

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Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable η Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the great eruption. We present the 2.4-670 μm spectral energy distribution, constructed from legacy Infrared Space Observatory observations and new spectroscopy obtained with the Herschel Space Observatory. Using radiative transfer modeling, we find that the two best-fit dust models yield compositions that are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Spherical corundum grains are supported by the good match to a narrow 20.2 μm feature. Our preferred model contains nitrides AlN and Si 3 N 4 in low abundances. Dust masses range from 0.25 to 0.44tot in both cases, due to an expected high Fe gas-to-dust ratio. The bulk of dust is within a ´ 5 7 central region. An additional compact feature is detected at 390 μm. We obtain L IR = 2.96×10 6  L , a 25% decline from an average of mid-IR photometric levels observed in 1971-1977. This indicates a reduction in circumstellar extinction in conjunction with an increase in visual brightness, allowing 25%-40% of optical and UV radiation to escape from the central source. We also present an analysis of 12 CO and 13 CO J=5-4 through 9-8 lines, showing that the abundances are consistent with expectations for CNO-processed material. The [ 12 C II] line is detected in absorption, which we suspect originates in foreground material at very low excitation temperatures.

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Section: Future Workmentioning

confidence: 99%

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Morris

Gull

Hillier

et al. 2017

ApJ

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“…The SOFIA-FORCAST (Herter et al 2012) observations of G35.2 were performed on 2011 May 24 and 26 (UT) in the 11.3, 19.7, 31.5, and 37.1 μm filters at an altitude of 43,000 feet. The chopping secondary of SOFIA was driven at 4 Hz, with a matched chop and nod throw of 60 , and with a nod performed every 30 s. The final effective on-source exposure times were 909 s at 11.3 μm, 959 s at 19.7 μm, 4068 s at 31.5 μm, and 4801 s at 37.1 μm.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…The chopping secondary of SOFIA was driven at 4 Hz, with a matched chop and nod throw of 60 , and with a nod performed every 30 s. The final effective on-source exposure times were 909 s at 11.3 μm, 959 s at 19.7 μm, 4068 s at 31.5 μm, and 4801 s at 37.1 μm. The fluxes were calibrated by the SOFIA data reduction pipeline, which during the Basic Science period has an estimated 3σ 20% calibration error in all filters (Herter et al 2012).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

A Massive Protostar Forming by Ordered Collapse of a Dense, Massive Core

Zhang

Tan

Buizer

et al. 2013

ApJ

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We present 30 and 40 μm imaging of the massive protostar G35.20−0.74 with SOFIA-FORCAST. The high surface density of the natal core around the protostar leads to high extinction, even at these relatively long wavelengths, causing the observed flux to be dominated by that emerging from the near-facing outflow cavity. However, emission from the far-facing cavity is still clearly detected. We combine these results with fluxes from the near-infrared to mm to construct a spectral energy distribution (SED). For isotropic emission the bolometric luminosity would be 3.3 × 10 4 L . We perform radiative transfer modeling of a protostar forming by ordered, symmetric collapse from a massive core bounded by a clump with high-mass surface density, Σ cl . To fit the SED requires protostellar masses ∼20-34 M depending on the outflow cavity opening angle (35 • -50 • ), and Σ cl ∼ 0.4-1 g cm −2 . After accounting for the foreground extinction and the flashlight effect, the true bolometric luminosity is ∼(0.7-2.2) × 10 5 L . One of these models also has excellent agreement with the observed intensity profiles along the outflow axis at 10, 18, 31, and 37 μm. Overall our results support a model of massive star formation involving the relatively ordered, symmetric collapse of a massive, dense core and the launching bipolar outflows that clear low-density cavities. Thus a unified model may apply for the formation of both low-and high-mass stars.

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“…The FORCAST instrument (Adams et al 2010;Herter et al 2012) on the Stratospheric Observatory for Infrared Astronomy (SOFIA; Young et al 2012) obtains mid-infrared images and spectra at 5.4-37.1μm on two detectors: the shortwavelength channel (SWC), and the long-wavelength channel (LWC). Using a dichroic, these channels simultaneously image two wavebands; alternatively, a single channel may be used to directly image one waveband.…”

Section: Forcast Filters and Sensitivitiesmentioning

confidence: 99%

The Power of SOFIA/FORCAST in Estimating Internal Luminosities of Low-mass Class 0/I Protostars

Huard

Terebey

2017

ApJ

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With the Stratospheric Observatory for Infrared Astronomy (SOFIA) routinely operating science flights, we demonstrate that observations with the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) can provide reliable estimates of the internal luminosities, L int , of protostars. We have developed a technique to estimate L int using a pair of FORCAST filters: one "short-wavelength" filter centered within 19.7-25.3μm, and one "long-wavelength" filter within 31.5-37.1μm. These L int estimates are reliable to within 30%-40% for 67% of protostars and to within a factor of 2.3-2.6 for 99% of protostars. The filter pair comprised of F 25.3 μm and F 37.1 μm achieves the best sensitivity and most constrained results. We evaluate several assumptions that could lead to systematic uncertainties. The OH5 dust opacity matches observational constraints for protostellar environments best, although not perfectly; we find that any improved dust model will have a small impact of 5%-10% on the L int estimates. For protostellar envelopes, the TSC84 model yields masses that are twice those of the Ulrich model, but we conclude that this mass difference does not significantly impact results at the mid-infrared wavelengths probed by FORCAST. Thus, FORCAST is a powerful instrument for luminosity studies targeting newly discovered protostars or suspected protostars lacking detections longward of 24μm. Furthermore, with its dynamic range and greater angular resolution, FORCAST may be used to characterize protostars that were either saturated or merged with other sources in previous surveys using the Spitzer Space Telescope or the Herschel Space Observatory.

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First Science Observations With Sofia/Forcast: The Forcast Mid-Infrared Camera

Cited by 107 publications

References 7 publications

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

A Massive Protostar Forming by Ordered Collapse of a Dense, Massive Core

The Power of SOFIA/FORCAST in Estimating Internal Luminosities of Low-mass Class 0/I Protostars

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