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RISS 인기검색어
- 검색키워드
- 저자 : JOAQUIN BOHIGAS (검색결과 4 건)
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PHYSICAL PROPERTIES OF THE GIANT H II REGION G353.2+0.9 IN NGC 6357
BOHIGAS JOAQUIN,TAPIA MAURICIO,ROTH MIGUEL,RUlZ MARIA TERESA The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.4
Optical imaging and spectroscopy of G353.2+0.9, the brightest part of the giant H II region NGC 6357, shows that this H II region is optically thin, contains ${\~}300\;M_{\bigodot}$ of ionized gas and is probably expanding into the surrounding medium. Its chemical composition is similar to that found in other H II regions at similar galactocentric distances if temperature fluctuations are significant. The inner regions are probably made of thin shells and filaments, whereas extended slabs of material, maybe shells seen edge-on, are found in the periphery. The radio continuum and H$\alpha$ emission maps are very similar, indicating that most of the optical nebula is not embedded in the denser regions traced by molecular gas and the presence of IR sources. About $10^{50}$ UV photons per second are required to produce the H$\beta$ flux from the 1l.3'${\times}$10' region surrounding the Pis 24 cluster that is south of G353.2+0.9. Most of the energy powering this region is produced by the 03-7 stars in Pis 24. Most of the 2MASS sources in the field with large infrared excesses are within G353.2+0.9, indicating that the most recent star forming process occured within it. The formation of Pis 24 preceded and caused the formation of this new generation of stars and may be responsible for the present-day morphology of the entire NGC 6357 region.
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SH 2-128, AN H II AND STAR FORMING REGION IN AN UNLIKELY PLACE
BOHIGAS JOAQUIN,TAPIA MAURICIO The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.4
Near-infrared imaging photometry supplemented by optical spectroscopy and narrow-band imaging of the H II region Sh 2-128 and its environment are presented. This region contains a developed H II region and the neighboring compact H II region S 128N associated with a pair of water maser sources. Midway between these, the core of a CO cloud is located. The principal ionizing source of Sh 2-128 is an 07 star close to its center. A new spectroscopic distance of 9.4 kpc is derived, very similar to the kinematic distance to the nebula. This implies a galactocentric distance of 13.5 kpc and z = 550 pc. The region is optically thin with abundances close to those predicted by galactocentric gradients. The $JHK_s$ images show that S 128N contains several infrared point sources and nebular emission knots with large near-infrared excesses. One of the three red Ks knots coincides with the compact H II region. A few of the infrared-excess objects are close to known mid- and far-infrared emission peaks. Star counts in J and $K_s$ show the presence of a small cluster of B-type stars, mainly associated with S 128N. The $JHK_s$ photometric properties together with the characteristics of the other objects in the vicinity suggest that Sh 2-128 and S 128N constitute a single complex formed from the same molecular cloud, with ages ${\~}10^6$ and < $3 {\times} 10^5$ years respectively. No molecular hydrogen emission was detected at 2.12 ${\mu}m$. The origin of this remote star forming region is an open problem.
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PHYSICAL PROPERTIES OF THE GIANT H II REGION G353.2+0.9 IN NGC 6357
JOAQUIN BOHIGAS,MIGUEL ROTH,MARIA TERESA RUIZ,MAURICIO TAPIA 한국천문학회 2004 Journal of The Korean Astronomical Society Vol.37 No.5
Optical imaging and spectroscopy of G353.2+0.9, the brightest part of the giant H II regionNGC 6357, shows that this H II region is optically thin, contains 300 M of ionized gas and isprobably expanding into the surrounding medium. Its chemical composition is similar to that found inother H II regions at similar galactocentric distances if temperature uctuations are signicant. Theinner regions are probably made of thin shells and laments, whereas extended slabs of material, maybeshells seen edge-on, are found in the periphery. The radio continuum and H-alpha emission maps are verysimilar, indicating that most of the optical nebula is not embedded in the denser regions traced bymolecular gas and the presence of IR sources. About 10^50 UV photons per second are required to pro-duce the H-beta flux from the 11.3'x10' region surrounding the Pis 24 cluster that is south of G353.2+0.9.Most of the energy powering this region is produced by the O3-7 stars in Pis 24. Most of the 2MASSsources in the eld with large infrared excesses are within G353.2+0.9, indicating that the most recentstar forming process occured within it. The formation of P is 24 preceded and caused the formation ofthis new generation of stars and may be responsible for the present-day morphology of the entire NGC6357 region.
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SH 2-128, AN H II AND STAR FORMING REGION IN AN UNLIKELY PLACE
JOAQUIN BOHIGAS,MAURICIO TAPIA 한국천문학회 2004 Journal of The Korean Astronomical Society Vol.37 No.5
Near-infrared imaging photometry supplemented by optical spectroscopy and narrow-band imagingof the H II region Sh 2-128 and its environment are presented. This region contains a developed H II region and the neighboring compact H II region S 128N associated with a pair of water maser sources.Midway between these, the core of a CO cloud is located. The principal ionizing source of Sh 2-128 isan O7 star close to its center. A new spectroscopic distance of 9.4 kpc is derived, very similar to thekinematic distance to the nebula. This implies a galactocentric distance of 13.5 kpc and z = 550 pc.The region is optically thin with abundances close to those predicted by galactocentric gradients. TheJHKs images show that S 128N contains several infrared point sources and nebular emission knots withlarge near-infrared excesses. One of the three redKs knots coincides with the compact H I region.A few of the infrared-excess objects are close to known mid- and far-infrared emission peaks. Starcounts inJ and Ks show the presence of a small cluster of B-type stars, mainly associated with S 128N.The JHKs photometric properties together with the characteristics of the other objects in the vicinitysuggest that Sh 2-128 and S 128N constitute a single complex formed from the same molecular cloud,with ages 10^6 and < 3 10^5 years respectively. No molecular hydrogen emission was detected at2.12m. The origin of this remote star forming region is an open problem.
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