Mon. Not. R. Astron. Soc., 443, 3218-3237 (2014/October-1)
NGC 7538: multiwavelength study of stellar cluster regions associated with IRS 1-3 and IRS 9 sources.
MALLICK K.K., OJHA D.K., TAMURA M., PANDEY A.K., DIB S., GHOSH S.K., SUNADA K., ZINCHENKO I., PIROGOV L. and TSUJIMOTO M.
Abstract (from CDS):
We present deep and high-resolution (FWHM ∼ 0.4 arcsec) near-infrared (NIR) imaging observations of the NGC 7538 IRS 1-3 region (in JHK bands), and IRS 9 region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is complemented with Giant Metrewave Radio Telescope (GMRT) low-frequency observations at 325, 610, and 1280 MHz, molecular line observations of H13CO+ (J=1-0), and archival Chandra X-ray observations. Using the `J - H/H - K' diagram, 144 Class II and 24 Class I young stellar object (YSO) candidates are identified in the IRS 1-3 region. Further analysis using `K/H - K' diagram yields 145 and 96 red sources in the IRS 1-3 and IRS 9 regions, respectively. A total of 27 sources are found to have X-ray counterparts. The YSO mass function (MF), constructed using a theoretical mass-luminosity relation, shows peaks at substellar ( ∼ 0.08-0.18M☉) and intermediate ( ∼ 1-1.78M☉) mass ranges for the IRS 1-3 region. The MF can be fitted by a power law in the low-mass regime with a slope of Γ ∼ 0.54-0.75, which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2 is obtained for the star to brown dwarf ratio in the IRS 1-3 region. GMRT maps show a compact H ii region associated with the IRS 1-3 sources, whose spectral index of 0.87±0.11 suggests optical thickness. This compact region is resolved into three separate peaks in higher resolution 1280 MHz map, and the `east' subpeak coincides with the IRS 2 source. H13CO+ (J=1-0) emission reveals peaks in both IRS 1-3 and IRS 9 regions, none of which are coincident with visible nebular emission, suggesting the presence of dense cloud nearby. The virial masses are approximately of the order of 1000 and 500M☉ for the clumps in IRS 1-3 and IRS 9 regions, respectively.
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
stars: luminosity function, mass function - ISM: individual objects: NGC 7538 - ISM: molecules - infrared: ISM - radio continuum: ISM - X-rays: stars
VizieR on-line data:
<Available at CDS (J/MNRAS/443/3218): table3.dat table4.dat table5.dat>
Table 3: [MOT2014] JHHMMSS.ss+DDMMSS.s N=27. Tables 4-5: [MOT2014] DDD.dddddd+DD.dddddd N=564+95.
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