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The MPIA conference series
at Ringberg Castle
The MPIA conference series
at Ringberg Castle
 
EPoS 2020 Suggested Contribution
Infrared study of a star-forming region associated with UC HII G45.07+0.13 and G45.12+0.13 regions

Elena Nikoghosyan
BAO, Yerevan, AM
We present the infrared study of a molecular cloud, which includes G45.12+0.13 (IRAS 19111+1048) and G45.07+0.13 (IRAS 19110+1045) UC HII regions. Using the Modified blackbody fitting on Herschel images we obtained that in UC HII regions the N(H2) increases from the center to the periphery, from 4×1022 to 3×1023 cm-2. In the regions where the blue lobes of the molecular outflows and the bridge between the regions of UC HII are located, the N(H2) increases. The distribution of the Td in both UC HII regions has a pronounced spherical symmetry. The maximum of Td in G45.12+0.13 is 49 K and 97K in G45.07+0.13. The evolutionary ages of G45.12+0.13 is 3.3×105 years and that of G45.07+0.13 is 2.3×105 years. Based on NIR, MIR, and FIR photometric data, we identified a young stellar population in the molecular cloud: about 1000 objects with different evolutionary stages from Class 0 to II. The Mass vs. Log(Age) and the CMD diagrams revealed the presence of two generations of the stellar population in the molecular cloud. The 1st generation includes stellar objects with both high and middle masses and with evolutionary stages from 0 to II. The KLF of these objects has not a sharp decline in the end. The α slope of KLF is 0.23 ± 0.09 that agrees well with Salpeter type IMF (γ=1.35) for a high mass range (O-F stars, β ∼ 2) at 1 Myr. The 2nd generation contains only middle mass stellar objects with 0 and I evolutionary stages. The KLF of the 2nd generation has a sharp decline. The α-slope of KLF of the objects of this group is 0.56 ± 0.09 that also agrees well with Salpeter type IMF, but for low-mass objects (G-M stars,β ∼ 1). The stellar objects are distributed nonuniformly in the molecular cloud and form two dense subgroups in the vicinity of the IRAS sources, which include only the objects from 1st generation. The central object of G45.12+0.13 UC HII, IRAS 19111+1048, is a star with 9.4 Msol mass and 2.5×106 years evolutionary age. Based on the results, we concluded that in the molecular cloud there were at least two star-formation waves. Currently, the stellar cluster in the molecular cloud is in the early stages of the star-forming process (SFE < 1%).
Caption: Up panel. Color-composite images of the Td (red) and N(H2) (green) distribution of the region surrounding G45.12+0.13 and G45.07+0.13 UCHII regions with overlaid contours of N(H2) in the left panel and Td in the right panel. The N(H2) contours cover a range from 1.3×1023 to 5.3×1023 cm-2 with step in increments of 0.8×1023 cm-2. The temperature contours cover a range from 12 to 66 K with step in increments of 6 K. The positions of IRAS sources are marked by white crosses. On the left panel, the positions of G45.12+0.13 outflow and bridge between UCHII regions are indicated. Down left panel. Mass vs. Log (Age) diagram. Filled circles and squares are 1st and 2nd generations, respectively. Class II, Class I, and Class 0 YSOs are indicated with blue, red and black colors, respectively. IRAS 19111+1048 source is indicated by a red triangle and it is labeled. Down right panel. Distribution of two stellar generations in the region on N(H2) map. The objects of 1st generation are marked by blue circles and of 2nd generation by red circles.
Collaborators:
N. Azatyan, BAO, AM
H. Harutyunian, BAO, AM
D. Bakhdasaryan, BAO, AM
D. Andreasyan, BAO, AM
Suggested Session: High-Mass Star Formation