Shih-Ying Hsu - Academia.edu (original) (raw)
Papers by Shih-Ying Hsu
The Astrophysical Journal
The presence of complex organic molecules (COMs) in the interstellar medium is of great interest ... more The presence of complex organic molecules (COMs) in the interstellar medium is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All of the hot corino sources discovered are likely Class 0, and their sizes of the warm region (>100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with the total number of methanol and the extent of its emissions. Such correlations are consistent with the thermal desorption picture for the presence of hot corinos and suggest that the lower-luminosity (Class 0) s...
The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great int... more The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All the hot corino sources discovered are likely Class 0 and their sizes of the warm region (> 100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with
The Astrophysical Journal
Prestellar cores are self-gravitating dense and cold structures within molecular clouds where fut... more Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high density (sub)structures on the thousand-au scale in a sample of dense prestellar cores. Through our recent ALMA observations towards the Orion molecular cloud, we have found five extremely dense prestellar cores, which have centrally concentrated regions ∼ 2000 au in size, and several 10 7 cm −3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89 M. For the first time, our higher resolution observations (0.8 ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800-1700 au, masses of 0.08 to 0.84 M , densities of 2 − 8 × 10 7 cm −3 , and separations of ∼ 1200 au. The substructures are massive enough (0.1 M) to form young stellar objects and are likely examples of the earliest stage of stellar embryos which can lead to widely (∼ 1200 au) separated multiple systems.
The Astrophysical Journal Supplement Series
Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early p... more Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm (band 6) using three different configurations (resolutions ∼ 0. 35, 1. 0, and 7. 0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3 mm continuum and molecular line emission (12 CO, and SiO) at an angular resolution of ∼ 0. 35 (∼ 140 au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust-mass ∼ 0.093 M and deconvolved size ∼ 0. 27. Dense substructures are clearly detected within the central 1000 au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity-extents (∆Vs) span from 4 to 110 km/s with outflow cavity opening angle width at 400 au ranging from [Θ obs ] 400 ∼ 0. 6 to 3. 9, which corresponds to 33. • 4−125. • 7. For the majority of the outflow sources, the ∆Vs show a positive correlation with [Θ obs ] 400 , suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.
The Astrophysical Journal
Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium... more Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium. In an effort to address this, forty-one Planck Galactic Cold Clumps at high Galactic latitude (HGal; |b| > 25 •) were observed in 12 CO, 13 CO and C 18 O J=1-0 lines, using the Purple Mountain Observatory 13.7-m telescope. 12 CO (1-0) and 13 CO (1-0) emission was detected in all clumps while C 18 O (1-0) emission was only seen in sixteen clumps. The highest and average latitudes are 71.4 • and 37.8 • , respectively. Fifty-one velocity components were obtained and then each was identified as a single clump. Thirty-three clumps were further mapped at 1 resolution and 54 dense cores were extracted. Among dense cores, the average excitation temperature T ex of 12 CO is 10.3 K. The average line widths of thermal and non-thermal velocity dispersions are 0.19 km s −1 and 0.46 km s −1 respectively, suggesting that these cores are dominated by turbulence. Distances of the HGal clumps given by Gaia dust reddening are about 120 − 360 pc. The ratio of X 13 /X 18 is significantly higher than that in the solar neighbourhood, implying that HGal gas has a different star formation history compared to the gas in the Galactic disk. HGal cores with sizes from 0.01 − 0.1 pc show no notable Larson's relation and the turbulence remains supersonic down to a scale of slightly below 0.1 pc. None of the HGal cores which bear masses from 0.01-1 M are gravitationally bound and all appear to be confined by outer pressure.
The Astrophysical Journal
The presence of complex organic molecules (COMs) in the interstellar medium is of great interest ... more The presence of complex organic molecules (COMs) in the interstellar medium is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All of the hot corino sources discovered are likely Class 0, and their sizes of the warm region (>100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with the total number of methanol and the extent of its emissions. Such correlations are consistent with the thermal desorption picture for the presence of hot corinos and suggest that the lower-luminosity (Class 0) s...
The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great int... more The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All the hot corino sources discovered are likely Class 0 and their sizes of the warm region (> 100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with
The Astrophysical Journal
Prestellar cores are self-gravitating dense and cold structures within molecular clouds where fut... more Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high density (sub)structures on the thousand-au scale in a sample of dense prestellar cores. Through our recent ALMA observations towards the Orion molecular cloud, we have found five extremely dense prestellar cores, which have centrally concentrated regions ∼ 2000 au in size, and several 10 7 cm −3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89 M. For the first time, our higher resolution observations (0.8 ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800-1700 au, masses of 0.08 to 0.84 M , densities of 2 − 8 × 10 7 cm −3 , and separations of ∼ 1200 au. The substructures are massive enough (0.1 M) to form young stellar objects and are likely examples of the earliest stage of stellar embryos which can lead to widely (∼ 1200 au) separated multiple systems.
The Astrophysical Journal Supplement Series
Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early p... more Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm (band 6) using three different configurations (resolutions ∼ 0. 35, 1. 0, and 7. 0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3 mm continuum and molecular line emission (12 CO, and SiO) at an angular resolution of ∼ 0. 35 (∼ 140 au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust-mass ∼ 0.093 M and deconvolved size ∼ 0. 27. Dense substructures are clearly detected within the central 1000 au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity-extents (∆Vs) span from 4 to 110 km/s with outflow cavity opening angle width at 400 au ranging from [Θ obs ] 400 ∼ 0. 6 to 3. 9, which corresponds to 33. • 4−125. • 7. For the majority of the outflow sources, the ∆Vs show a positive correlation with [Θ obs ] 400 , suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.
The Astrophysical Journal
Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium... more Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium. In an effort to address this, forty-one Planck Galactic Cold Clumps at high Galactic latitude (HGal; |b| > 25 •) were observed in 12 CO, 13 CO and C 18 O J=1-0 lines, using the Purple Mountain Observatory 13.7-m telescope. 12 CO (1-0) and 13 CO (1-0) emission was detected in all clumps while C 18 O (1-0) emission was only seen in sixteen clumps. The highest and average latitudes are 71.4 • and 37.8 • , respectively. Fifty-one velocity components were obtained and then each was identified as a single clump. Thirty-three clumps were further mapped at 1 resolution and 54 dense cores were extracted. Among dense cores, the average excitation temperature T ex of 12 CO is 10.3 K. The average line widths of thermal and non-thermal velocity dispersions are 0.19 km s −1 and 0.46 km s −1 respectively, suggesting that these cores are dominated by turbulence. Distances of the HGal clumps given by Gaia dust reddening are about 120 − 360 pc. The ratio of X 13 /X 18 is significantly higher than that in the solar neighbourhood, implying that HGal gas has a different star formation history compared to the gas in the Galactic disk. HGal cores with sizes from 0.01 − 0.1 pc show no notable Larson's relation and the turbulence remains supersonic down to a scale of slightly below 0.1 pc. None of the HGal cores which bear masses from 0.01-1 M are gravitationally bound and all appear to be confined by outer pressure.