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Title: A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS

Abstract

We report a multi-epoch, simultaneous 22 GHz H{sub 2}O and 44 GHz Class I CH{sub 3}OH maser line survey toward 180 intermediate-mass young stellar objects, including 14 Class 0 and 19 Class I objects, and 147 Herbig Ae/Be stars. We detected H{sub 2}O and CH{sub 3}OH maser emission toward 16 (9%) and 10 (6%) sources with one new H{sub 2}O and six new CH{sub 3}OH maser sources. The detection rates of both masers rapidly decrease as the central (proto)stars evolve, which is contrary to the trends in high-mass star-forming regions. This suggests that the excitations of the two masers are closely related to the evolutionary stage of the central (proto)stars and the circumstellar environments. H{sub 2}O maser velocities deviate on average 9 km s{sup -1} from the ambient gas velocities whereas CH{sub 3}OH maser velocities match quite well with the ambient gas velocities. For both maser emissions, large velocity differences (|v{sub H{sub 2}O} - v{sub sys}| > 10kms{sup -1} and |v{sub CH3OH} - v{sub sys}| > 1kms{sup -1}) are mostly confined to Class 0 objects. The formation and disappearance of H{sub 2}O masers is frequent and their integrated intensities change by up to two orders of magnitude. In contrast, CH{submore » 3}OH maser lines usually show no significant change in intensity, shape, or velocity. This is consistent with the previous suggestion that H{sub 2}O maser emission originates from the base of an outflow while 44 GHz Class I CH{sub 3}OH maser emission arises from the interaction region of the outflow with the ambient gas. The isotropic maser luminosities are well correlated with the bolometric luminosities of the central objects. The fitted relations are L{sub H2O}= 1.71x10{sup -9}(L{sub bol}){sup 0.97} and L{sub CH3OH}= 1.71x10{sup -10}(L{sub bol}){sup 1.22}.« less

Authors:
; ; ; ; ; ;  [1]
  1. Korea Astronomy and Space Science Institute, Hwaam-Dong, Yuseong-Gu, Daejeon 305-348 (Korea, Republic of)
Publication Date:
OSTI Identifier:
21560317
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal, Supplement Series
Additional Journal Information:
Journal Volume: 196; Journal Issue: 2; Other Information: DOI: 10.1088/0067-0049/196/2/21; Journal ID: ISSN 0067-0049
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; LUMINOSITY; MASERS; METHANOL; PROTOSTARS; STARS; VELOCITY; WATER; ALCOHOLS; AMPLIFIERS; ELECTRONIC EQUIPMENT; EQUIPMENT; HYDROGEN COMPOUNDS; HYDROXY COMPOUNDS; MICROWAVE AMPLIFIERS; MICROWAVE EQUIPMENT; OPTICAL PROPERTIES; ORGANIC COMPOUNDS; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES

Citation Formats

Bae, Jae-Han, Kim, Kee-Tae, Youn, So-Young, Kim, Won-Ju, Byun, Do-Young, Kang, Hyunwoo, and Oh, Chung Sik, E-mail: jaehbae@umich.edu, E-mail: whorujh@kasi.re.kr, E-mail: ktkim@kasi.re.kr. A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS. United States: N. p., 2011. Web. doi:10.1088/0067-0049/196/2/21.
Bae, Jae-Han, Kim, Kee-Tae, Youn, So-Young, Kim, Won-Ju, Byun, Do-Young, Kang, Hyunwoo, & Oh, Chung Sik, E-mail: jaehbae@umich.edu, E-mail: whorujh@kasi.re.kr, E-mail: ktkim@kasi.re.kr. A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS. United States. doi:10.1088/0067-0049/196/2/21.
Bae, Jae-Han, Kim, Kee-Tae, Youn, So-Young, Kim, Won-Ju, Byun, Do-Young, Kang, Hyunwoo, and Oh, Chung Sik, E-mail: jaehbae@umich.edu, E-mail: whorujh@kasi.re.kr, E-mail: ktkim@kasi.re.kr. Sat . "A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS". United States. doi:10.1088/0067-0049/196/2/21.
@article{osti_21560317,
title = {A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS},
author = {Bae, Jae-Han and Kim, Kee-Tae and Youn, So-Young and Kim, Won-Ju and Byun, Do-Young and Kang, Hyunwoo and Oh, Chung Sik, E-mail: jaehbae@umich.edu, E-mail: whorujh@kasi.re.kr, E-mail: ktkim@kasi.re.kr},
abstractNote = {We report a multi-epoch, simultaneous 22 GHz H{sub 2}O and 44 GHz Class I CH{sub 3}OH maser line survey toward 180 intermediate-mass young stellar objects, including 14 Class 0 and 19 Class I objects, and 147 Herbig Ae/Be stars. We detected H{sub 2}O and CH{sub 3}OH maser emission toward 16 (9%) and 10 (6%) sources with one new H{sub 2}O and six new CH{sub 3}OH maser sources. The detection rates of both masers rapidly decrease as the central (proto)stars evolve, which is contrary to the trends in high-mass star-forming regions. This suggests that the excitations of the two masers are closely related to the evolutionary stage of the central (proto)stars and the circumstellar environments. H{sub 2}O maser velocities deviate on average 9 km s{sup -1} from the ambient gas velocities whereas CH{sub 3}OH maser velocities match quite well with the ambient gas velocities. For both maser emissions, large velocity differences (|v{sub H{sub 2}O} - v{sub sys}| > 10kms{sup -1} and |v{sub CH3OH} - v{sub sys}| > 1kms{sup -1}) are mostly confined to Class 0 objects. The formation and disappearance of H{sub 2}O masers is frequent and their integrated intensities change by up to two orders of magnitude. In contrast, CH{sub 3}OH maser lines usually show no significant change in intensity, shape, or velocity. This is consistent with the previous suggestion that H{sub 2}O maser emission originates from the base of an outflow while 44 GHz Class I CH{sub 3}OH maser emission arises from the interaction region of the outflow with the ambient gas. The isotropic maser luminosities are well correlated with the bolometric luminosities of the central objects. The fitted relations are L{sub H2O}= 1.71x10{sup -9}(L{sub bol}){sup 0.97} and L{sub CH3OH}= 1.71x10{sup -10}(L{sub bol}){sup 1.22}.},
doi = {10.1088/0067-0049/196/2/21},
journal = {Astrophysical Journal, Supplement Series},
issn = {0067-0049},
number = 2,
volume = 196,
place = {United States},
year = {2011},
month = {10}
}