Browsing by Subject "dark-cloud"

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Dust, Ice, and Gas in Time (DIGIT) Herschel Observations of GSS30-IRS1 in Ophiuchus
(2015-03) Je, Hyerin; Lee, Jeong-Eun; Lee, Seokho; Green, Joel D.; Evans, Neal J., II; ee, Jeong-Eun; Green, Joel D.; Evans, Neal J., II
As a part of the "Dust, Ice, and Gas In Time" (DIGIT) key program on Herschel, we observed GSS30-IRS1, a Class I protostar located in Ophiuchus (d = 120 pc), with Herschel/Photodetector Array Camera and Spectrometer. More than 70 lines were detected within a wavelength range from 50 to 200 mu m, including CO, H2O, OH, and two atomic [O I] lines at 63 and 145 mu m. The [C II] line, known as a tracer of externally heated gas by the interstellar radiation field (ISRF), is also detected at 158 mu m. All lines, except [O I] and [C II], are detected only at the central spaxel of 9 ''.4 x 9 ''.4. The [O I] emissions are extended along a NE-SW orientation, and the [C II] line is detected over all spaxels, indicative of an external photodissociation region. The total [C II] intensity around GSS30 reveals that the far-ultraviolet radiation field is in the range of 3 to 20 G(0), where G(0) is in units of the Habing Field, 1.6 x 10(-3) erg cm(-2) s(-1). This enhanced external radiation field heats the envelope of GSS30-IRS1, causing the continuum emission to be extended, unlike the molecular emission. The best-fit continuum model of GSS30-IRS1 with the physical structure including flared disk, envelope, and outflow shows that the internal luminosity is 10 L-circle dot, and the region is externally heated by a radiation field enhanced by a factor of 130 compared to the standard local ISRF.
The Spitzer c2d Survey Of Large, Nearby, Interstellar Clouds. VII. Ophiuchus Observed With MIPS
(2008-01) Padgett, Deborah L.; Rebull, L. M.; Stapelfeldt, Karl R.; Chapman, Nicholas L.; Lai, Shih-Ping; Mundy, Lee G.; Evans, Neal J.; Brooke, Tyler Y.; Cieza, Lucas A.; Spiesman, William J.; Noriega-Crespo, Alberto; McCabe, Caer-Eve; Allen, Lori E.; Blake, Geoffrey A.; Harvey, Paul M.; Huard, Tracy L.; Jorgensen, Jes K.; Koerner, David W.; Myers, Phillip C.; Sargent, Anneila I.; Teuben, Peter; van Dishoeck, Ewine F.; Wahhaj, Zahed; Young, Kaisa E.; Spiesman, William J.; Evans, Neal J.; Harvey, Paul M.; Young, Kaisa E.
We present maps of 14.4 deg(2) of the Ophiuchus dark clouds observed by the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer ( MIPS). These high-quality maps depict both numerous point sources and extended dust emission within the star-forming and non-star-forming portions of these clouds. Using PSF-fitting photometry, we detect 5779 sources at 24 mu m and 81 sources at 70 mu m at the 10 sigma level of significance. Three hundred twenty-three candidate young stellar objects ( YSOs) were identified according to their positions on the MIPS/2MASS K versus K - [24] color-magnitude diagrams, as compared to 24 mu m detections in the SWIRE extragalactic survey. We find that more than half of the YSO candidates, and almost all those with protostellar Class I spectral energy distributions, are confined to the known cluster and aggregates.
The Spitzer c2d Survey Of Large, Nearby, Interstellar Clouds. X. The Chamaeleon II Pre-Main-Sequence Population As Observed With IRAC And MIPS
(2008-03) Alcala, Juan M.; Spezzi, Loredana; Chapman, Nicholas; Evans, Neal J.; Huard, Tracy L.; Jorgensen, Jes K.; Merin, Bruno; Stapelfeldt, Karl R.; Covino, E.; Frasca, Antonio; Gandolfi, Davide; Oliveira, Isa; Evans, Neal J.
We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and NIR data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population in an area of similar to 1.75 deg(2) and study the spatial distribution and properties of the cloud members and candidate pre-main-sequence (PMS) objects and their circumstellar matter. Our census is complete down to the substellar regime (M approximate to 0.03 M-circle dot). From the analysis of the volume density of the PMS objects and candidates we find two groups of objects with volume densities higher than 25 M-circle dot pc(-3) and 5-10 members each. A multiplicity fraction of about 13% +/- 3% is observed for objects with separations 0.8 '' < theta < 6.0 '' (142-1065 AU). No evidence for variability between the two epochs of the c2d IRAC data set, Delta t similar to 6 hr, is detected. We estimate a star formation efficiency of 1%-4%, consistent with the estimates for Taurus and Lupus, but lower than for Cha I. This might mean that different star formation activities in the Chamaeleon clouds reflect a different history of star formation. We also find that Cha II is turning some 6-7 M-circle dot into stars every Myr, which is low in comparison with the star formation rate in other c2d clouds. The disk fraction of 70%-80% that we estimate in Cha II is much higher than in other star-forming regions and indicates that the population in this cloud is dominated by objects with active accretion. Finally, the Cha II outflows are discussed; a new Herbig-Haro outflow, HH 939, driven by the classical T Tauri star Sz 50, has been discovered.