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<i>SPITZER</i>AND HEINRICH HERTZ TELESCOPE OBSERVATIONS OF STARLESS CORES: MASSES AND ENVIRONMENTS
Stutz, Amelia M.,Rieke, George H.,Bieging, John H.,Balog, Zoltan,Heitsch, Fabian,Kang, Miju,Peters, William L.,Shirley, Yancy L.,Werner, Michael W. IOP Publishing 2009 The Astrophysical journal Vol.707 No.1
<P>We present Spitzer observations of a sample of 12 starless cores selected to have prominent 24 mu m shadows. The Spitzer images show 8 mu m and 24 mu m shadows and in some cases 70 mu m shadows; these spatially resolved absorption features trace the densest regions of the cores. We have carried out a (CO)-C-12 (2-1) and (CO)-C-13 (2-1) mapping survey of these cores with the Heinrich Hertz Telescope (HHT). We use the shadow features to derive optical depth maps. We derive molecular masses for the cores and the surrounding environment; we find that the 24 mu m shadow masses are always greater than or equal to the molecular masses derived in the same region, a discrepancy likely caused by CO freezeout onto dust grains. We combine this sample with two additional cores that we studied previously to bring the total sample to 14 cores. Using a simple Jeans mass criterion, we find that similar to 2/3 of the cores selected to have prominent 24 mu m shadows are collapsing or near collapse, a result that is supported by millimeter line observations. Of this subset at least half have indications of 70 mu m shadows. All cores observed to produce absorption features at 70 mu m are close to collapse. We conclude that 24 mu m shadows, and even more so the 70 mu m ones, are useful markers of cloud cores that are approaching collapse.</P>
MEASUREMENT OF HDCO/H<sub>2</sub>CO RATIOS IN THE ENVELOPES OF EXTREMELY COLD PROTOSTARS IN ORION
Kang, Miju,Choi, Minho,Stutz, Amelia M.,Tatematsu, Ken’ichi IOP Publishing 2015 The Astrophysical journal Vol.814 No.1
<P>We present observations of HDCO and H2CO emission toward a sample of 15 Class 0 protostars in the Orion A and B clouds. Of these, 11 protostars are Herschel-identified PACS Bright Red Sources (PBRSs) and 4 are previously identified protostars. Our observations revealed the chemical properties of the PBRS envelope for the first time. The column densities of HDCO and H2CO are derived from single-dish observations at an angular resolution of similar to 20 '' (similar to 8400 AU). The degree of deuteration in H2CO ([HDCO]/[H2CO]) was estimated to range from 0.03 to 0.31. The deuterium fractionation of most PBRSs (70%) is similar to that of the non-PBRS sources. Three PBRSs (30%) exhibit high deuterium fractionation, larger than 0.15. The large variation of the deuterium fractionation of H2CO in the whole PBRS sample may reflect the diversity in the initial conditions of star-forming cores. There is no clear correlation between the [HDCO]/[H2CO] ratio and the evolutionary sequence of protostars.</P>
Impact of high-resolution a priori profiles on satellite-based formaldehyde retrievals
Kim, Si-Wan,Natraj, Vijay,Lee, Seoyoung,Kwon, Hyeong-Ahn,Park, Rokjin,de Gouw, Joost,Frost, Gregory,Kim, Jhoon,Stutz, Jochen,Trainer, Michael,Tsai, Catalina,Warneke, Carsten Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.10
<P>Abstract. Formaldehyde (HCHO) is either directly emitted from sources or produced during the oxidation of volatile organic compounds (VOCs) in the troposphere. It is possible to infer atmospheric HCHO concentrations using space-based observations, which may be useful for studying emissions and tropospheric chemistry at urban to global scales depending on the quality of the retrievals. In the near future, an unprecedented volume of satellite-based HCHO measurement data will be available from both geostationary and polar-orbiting platforms. Therefore, it is essential to develop retrieval methods appropriate for the next-generation satellites that measure at higher spatial and temporal resolution than the current ones. In this study, we examine the importance of fine spatial and temporal resolution a priori profile information on the retrieval by conducting approximately 45 000 radiative transfer (RT) model calculations in the Los Angeles Basin (LA Basin) megacity. Our analyses suggest that an air mass factor (AMF, a factor converting observed slant columns to vertical columns) based on fine spatial and temporal resolution a priori profiles can better capture the spatial distributions of the enhanced HCHO plumes in an urban area than the nearly constant AMFs used for current operational products by increasing the columns by ∼ 50 % in the domain average and up to 100 % at a finer scale. For this urban area, the AMF values are inversely proportional to the magnitude of the HCHO mixing ratios in the boundary layer. Using our optimized model HCHO results in the Los Angeles Basin that mimic the HCHO retrievals from future geostationary satellites, we illustrate the effectiveness of HCHO data from geostationary measurements for understanding and predicting tropospheric ozone and its precursors. </P>