Reiko Yamaguchi
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Reiko Yamaguchi has a total of 16 co-authors. Here are the top co-authors by number of shared publications:
- Yasuo Fukui
Department of Physics, Nagoya University , Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601
5 shared publications - Norikazu Mizuno
Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
4 shared publications Toshikazu Onishi
Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602
3 shared publicationsAkira Mizuno
Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602
2 shared publications- Akira Mizuno
Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
2 shared publications - Toshikazu Onishi
Nagoya University
2 shared publications
Latest Publications
- Open Access
- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , L41-L44
On the Mass Spectrum of Giant Molecular Clouds in the Large Magellanic Cloud
Based on a new sensitive survey of the giant molecular clouds (GMCs) in the Large Magellanic Cloud, we derived the mass spectrum for them. In the mass range from $\sim8\times10^4\,{{{M}_{\odot}}}$ to $3\times10^6\,{{{M}_{\odot}}}$, a power law with an index value of $-1.9\pm0.1$ shows the best fit to the data. This is consistent with numerical simulations that explain both the H i and CO clumpy distributions by Wada et al. (2000; ApJ, 540, 797), but is significantly steeper than that of the GMCs in the Galaxy. This may be consistent with the drastic dissipation of the GMCs in the LMC due to higher UV radiation fields than in the Galaxy.- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , L41-L44
Open AccessOn the Mass Spectrum of Giant Molecular Clouds in the Large Magellanic Cloud
Based on a new sensitive survey of the giant molecular clouds (GMCs) in the Large Magellanic Cloud, we derived the mass spectrum for them. In the mass range from $\sim8\times10^4\,{{{M}_{\odot}}}$ to $3\times10^6\,{{{M}_{\odot}}}$, a power law with an index value of $-1.9\pm0.1$ shows the best fit to the data. This is consistent with numerical simulations that explain both the H i and CO clumpy distributions by Wada et al. (2000; ApJ, 540, 797), but is significantly steeper than that of the GMCs in the Galaxy. This may be consistent with the drastic dissipation of the GMCs in the LMC due to higher UV radiation fields than in the Galaxy. - Open Access
- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , 985-1001
A CO Survey of the LMC with NANTEN: III. Formation of Stellar Clusters and Evolution of Molecular Clouds
In order to elucidate star formation in the LMC, we made a complete study of CO clouds with NANTEN. In the present paper, we compare 55 giant molecular clouds (GMCs), whose physical quantities were well determined, with young objects, such as young stellar clusters and H ii regions. We find that the GMCs are actively forming stars and clusters; 23 and 40 are found to be associated with the clusters and the H ii regions, respectively. The clusters associated with the GMCs are significantly young; $$\sim 85\%$$ of them are younger than $$\sim 10 \,\mathrm{Myr}$$. In addition, compact groups of the young clusters are often found at the peak position of the GMCs, e.g., N 159 and N 44, while much looser groups are away from the GMCs. This suggests that the clusters are formed in groups and disperse as they become old. The distributions of the CO, [C ii], and UV indicate that the GMCs are likely to be rapidly dissipated within several Myr due to UV photons from the clusters. We also estimate the evolutionary time scale of the GMCs; they form stars in a few Myr after their birth, and form clusters during the next few Myr, and are dissipated in the subsequent few Myr.- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , 985-1001
Open AccessA CO Survey of the LMC with NANTEN: III. Formation of Stellar Clusters and Evolution of Molecular Clouds
In order to elucidate star formation in the LMC, we made a complete study of CO clouds with NANTEN. In the present paper, we compare 55 giant molecular clouds (GMCs), whose physical quantities were well determined, with young objects, such as young stellar clusters and H ii regions. We find that the GMCs are actively forming stars and clusters; 23 and 40 are found to be associated with the clusters and the H ii regions, respectively. The clusters associated with the GMCs are significantly young; $$\sim 85\%$$ of them are younger than $$\sim 10 \,\mathrm{Myr}$$. In addition, compact groups of the young clusters are often found at the peak position of the GMCs, e.g., N 159 and N 44, while much looser groups are away from the GMCs. This suggests that the clusters are formed in groups and disperse as they become old. The distributions of the CO, [C ii], and UV indicate that the GMCs are likely to be rapidly dissipated within several Myr due to UV photons from the clusters. We also estimate the evolutionary time scale of the GMCs; they form stars in a few Myr after their birth, and form clusters during the next few Myr, and are dissipated in the subsequent few Myr. - Open Access
- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , 959-969
Sensitive CO Observations of the LMC Supergiant Shells with NANTEN: Their Effects on the Formation of Molecular Clouds and Stellar Clusters
A statistical study of the effects of supergiant shells (SGSs) on the formation of stars and molecular clouds was made based on sensitive CO ($$J=1 \hbox{--} 0$$) observations of the molecular clouds in the LMC with NANTEN. The sensitive observations have detected 168 CO clouds whose mass ranges from $$\sim 4 \times 10^4 \,{{{M}_{\odot}}}$$ to $$3 \times 10^6 \,{{{M}_{\odot}}}$$. Out of the 168 clouds, 63 are associated with the SGSs, accounting for $$\gtrsim 35\%$$. The surface number and mass densities of the CO clouds are higher by a factor of 1.5–2 at the edge of the SGSs than elsewhere. This suggests the formation of CO clouds under the dynamical effects of the SGSs, such as the accumulation of interstellar medium. Young stellar clusters are more actively formed on the side of the CO clouds facing to the center of the SGSs, particularly where the $$\mathrm{H}\alpha$$ filaments are adjacent to the CO clouds. The number of clusters is increased by a factor of 2 on the side facing to the center of the SGSs with respect to the CO peaks compared with on the side far from the center. These results strongly suggest that cluster formation is triggered by dynamical effects of the SGSs. We find that $$\sim 60\%$$ of the young clusters are located within the boundary of the SGSs, and propose that a few 10% of the young clusters of $$\tau \lt 10 \,\mathrm{Myr}$$ have likely been formed due to dynamical effects of the SGSs.- 25 December 2001
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 53 (6) , 959-969
Open AccessSensitive CO Observations of the LMC Supergiant Shells with NANTEN: Their Effects on the Formation of Molecular Clouds and Stellar Clusters
A statistical study of the effects of supergiant shells (SGSs) on the formation of stars and molecular clouds was made based on sensitive CO ($$J=1 \hbox{--} 0$$) observations of the molecular clouds in the LMC with NANTEN. The sensitive observations have detected 168 CO clouds whose mass ranges from $$\sim 4 \times 10^4 \,{{{M}_{\odot}}}$$ to $$3 \times 10^6 \,{{{M}_{\odot}}}$$. Out of the 168 clouds, 63 are associated with the SGSs, accounting for $$\gtrsim 35\%$$. The surface number and mass densities of the CO clouds are higher by a factor of 1.5–2 at the edge of the SGSs than elsewhere. This suggests the formation of CO clouds under the dynamical effects of the SGSs, such as the accumulation of interstellar medium. Young stellar clusters are more actively formed on the side of the CO clouds facing to the center of the SGSs, particularly where the $$\mathrm{H}\alpha$$ filaments are adjacent to the CO clouds. The number of clusters is increased by a factor of 2 on the side facing to the center of the SGSs with respect to the CO peaks compared with on the side far from the center. These results strongly suggest that cluster formation is triggered by dynamical effects of the SGSs. We find that $$\sim 60\%$$ of the young clusters are located within the boundary of the SGSs, and propose that a few 10% of the young clusters of $$\tau \lt 10 \,\mathrm{Myr}$$ have likely been formed due to dynamical effects of the SGSs. - Open Access
- 1 June 2001
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 553 (2) , L185-L188
Molecular Clouds in the Supergiant Shell LMC 4: Evidence for Triggered Cluster Formation
We have completed fully sampled observations of CO (J = 1-0) toward the supergiant shell (SGS) LMC 4 at a linear resolution of 40 pc with NANTEN. The result is the discovery of 18 clumpy CO clouds, 17 of which well delineate the SGS traced by Hα and H I. The remaining one cloud inside the SGS exhibits a cometary shape with an H I tail heading toward the center of the SGS. A comparison between the CO clouds and the young stars, including H II regions and stellar clusters, indicates that all the associated young stars are on the side of the clouds facing toward the center of the SGS. The typical separation between the cloud peaks and young stars is ~40-100 pc. These facts strongly suggest that star formation has been triggered by the expanding shell that is driven by OB stars, indicating the important role of SGSs in cluster formation in the LMC.
- 1 June 2001
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 553 (2) , L185-L188
Open AccessMolecular Clouds in the Supergiant Shell LMC 4: Evidence for Triggered Cluster Formation
We have completed fully sampled observations of CO (J = 1-0) toward the supergiant shell (SGS) LMC 4 at a linear resolution of 40 pc with NANTEN. The result is the discovery of 18 clumpy CO clouds, 17 of which well delineate the SGS traced by Hα and H I. The remaining one cloud inside the SGS exhibits a cometary shape with an H I tail heading toward the center of the SGS. A comparison between the CO clouds and the young stars, including H II regions and stellar clusters, indicates that all the associated young stars are on the side of the clouds facing toward the center of the SGS. The typical separation between the cloud peaks and young stars is ~40-100 pc. These facts strongly suggest that star formation has been triggered by the expanding shell that is driven by OB stars, indicating the important role of SGSs in cluster formation in the LMC.
- Open Access
- 1 December 1999
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 51 (6) , 919-929
A New Derivation of the Extinct ion-to-CO Column Density Ratio in the Chamaeleon I Dark Cloud
We have analyzed new datasets of 13CO (J = 1−0) and C18O (J = 1−0) emission obtained with NANTEN and visual extinction, AV, derived from DENIS J-band observations in the Chamaeleon I dark cloud. The column densities of both molecular isotopes, N(13CO) and N(C18O, have been derived assuming LTE. Both N(13CO) and N(C18O are linearly correlated with AV in the range AV≲ 10 mag. We established the relationships N(13CO) (cm-2)=(1.2± 0.1)× 1015AV(mag)+(0.7± 0.3)× 1015 and N(C18O) (cm-2)=(3.5± 0.3)× 1014AV(mag)-(5.7± 1.3)× 1014. In a region of clustered T Tauri stars, however, both the AV-N(13CO) and AV-N(C18O) relationships are by a factor of ∼ 2 steeper than the above. This may be mainly due to underestimates of the AV values, and the J-band star count might deserve a more careful examination for possible underestimates of associated young stars. Compared with the relationships for the other clouds, the slope of the AV-N(13CO) relationship is relatively shallower and that of the AV-N(C18O) relationship in a non-cluster forming region is slightly steeper. These facts suggest that cloud-to-cloud variation is significant in the AV-N(CO) relationships.
- 1 December 1999
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 51 (6) , 919-929
Open AccessA New Derivation of the Extinct ion-to-CO Column Density Ratio in the Chamaeleon I Dark Cloud
We have analyzed new datasets of 13CO (J = 1−0) and C18O (J = 1−0) emission obtained with NANTEN and visual extinction, AV, derived from DENIS J-band observations in the Chamaeleon I dark cloud. The column densities of both molecular isotopes, N(13CO) and N(C18O, have been derived assuming LTE. Both N(13CO) and N(C18O are linearly correlated with AV in the range AV≲ 10 mag. We established the relationships N(13CO) (cm-2)=(1.2± 0.1)× 1015AV(mag)+(0.7± 0.3)× 1015 and N(C18O) (cm-2)=(3.5± 0.3)× 1014AV(mag)-(5.7± 1.3)× 1014. In a region of clustered T Tauri stars, however, both the AV-N(13CO) and AV-N(C18O) relationships are by a factor of ∼ 2 steeper than the above. This may be mainly due to underestimates of the AV values, and the J-band star count might deserve a more careful examination for possible underestimates of associated young stars. Compared with the relationships for the other clouds, the slope of the AV-N(13CO) relationship is relatively shallower and that of the AV-N(C18O) relationship in a non-cluster forming region is slightly steeper. These facts suggest that cloud-to-cloud variation is significant in the AV-N(CO) relationships.