WEKO3
アイテム
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In order for us to tackle this issue,it is crucial to understand how jets\u003cbr /\u003einteract with ambient material.\u003cbr /\u003e In addition to the kinematics,the mass loss rate and mass momentum\u003cbr /\u003etransfer rate of are key parameters to investigate how the jet interacts\u003cbr /\u003ewith the ambient material. However,the mass momentum is poorly known\u003cbr /\u003ebecause the hydrogen density is not easily derived, as is different from the\u003cbr /\u003eelectron density that is measured from forbidden line emissions. If we assume\u003cbr /\u003ethat a jet is fully ionized, i.e. the electron density is nearly equal to the\u003cbr /\u003ehydrogen density,the mass momentum of the jet derived from its optical\u003cbr /\u003eemission lines is not sufficient to drive the molecular outflow associated with\u003cbr /\u003eit. In contrast,recent studies have suggested that jets are almost neutral,\u003cbr /\u003eindicating that a jet may have momentum sufficient to drive a molecular outflow.\u003cbr /\u003e In order to study the issues described above,we made slit-scan observa-\u003cbr /\u003etions of Hα and [NII] 6583 \u0026Aring; emission lines toward two bright jets,HH46/47\u003cbr /\u003eand the HL Tau jet,with Subaru Telescope. The large diameter of the tele-\u003cbr /\u003escope,together with the high spectral resolution of the spectrograph(High\u003cbr /\u003eDispersion Spectrograph,R =3.6×10\u003csup\u003e40\u003c/sup\u003e or \u0026Delta;v=8km s\u003csup\u003e-1\u003c/sup\u003e)allowed us to\u003cbr /\u003estudy the kinematics of these jets in unprecedented detail.Furthermore,the\u003cbr /\u003eslit-scan technique with a long slit provided us with kinematic information\u003cbr /\u003eof the entire jets.\u003cbr /\u003e We found that,in both jets,the Hα emission traces both the main jet\u003cbr /\u003ecomponent(\u003ci\u003eV\u003c/i\u003e\u003csmall\u003eLSR\u003c/small\u003e=-160~-180km s\u003csup\u003e-1\u003c/sup\u003e)and distinct lower velocity com-\u003cbr /\u003eponent (|\u003ci\u003eV\u003c/i\u003e\u003csmall\u003eLSR\u003c/small\u003e| \u0026le; 120km s\u003csup\u003e-1\u003c/sup\u003e). The [NII] emission, on the other hand,is\u003cbr /\u003eprimarily associated with the main jet component and is much faint or ab-\u003cbr /\u003esent in the lower velocity component. In the HH 46/47 jet,the velocities\u003cbr /\u003eof Hαand [NII] emission lines match well in their main jet components.\u003cbr /\u003eThe lower velocity components are associated with one-sided bow shocks\u003cbr /\u003eand with one of the Hα filaments that was previous identified with the\u003cbr /\u003e\u003ci\u003eHubble Space Telescope.\u003c/i\u003e In the HL Tau jet,the lower velocity component\u003cbr /\u003eis associated with indivisual knots, which is explained by the lower velocity\u003cbr /\u003eemmituion arising in the laterals of bow shocks. While the main jet component\u003cbr /\u003eis associated with the ejecta, the lower velocity component is produced as a\u003cbr /\u003eresult of the interaction between the ejecta and the surrounding gas.\u003cbr /\u003e Observed Hα line profiles suggest that the shock velocities at the bow\u003cbr /\u003eshocks and the Hα filament with respect to the ambient gas are 60-80km s\u003csup\u003e-1\u003c/sup\u003e\u003cbr /\u003eand 120-130 km s\u003csup\u003e-1\u003c/sup\u003e for HH46/47 and HL Tau,respectively. These are\u003cbr /\u003emarkedly smaller than the three dimensional(3-D)velocities of the jets(~300\u003cbr /\u003ekm s\u003csup\u003e-1\u003c/sup\u003e). The discrepancy between the shock velocity and 3-D velocity is\u003cbr /\u003eexplained if the ambient gas moves outward by~200km s\u003csup\u003e-1.\u003c/sup\u003e. The velocity\u003cbr /\u003eof the ambient gas measured in the HH46/47 jet is similar to those of HH\u003cbr /\u003e47A and 47D,giant bow shocks ahead of the observed region.\u003cbr /\u003e Through detailed analysis,we concluded that the outward motion of the\u003cbr /\u003e ambient gas is a result of prompt entrainment,i.e. a jet sweeps up ambient\u003cbr /\u003ematerial at its head by a large bow shock,but not of turbulent entrainment,\u003cbr /\u003ethe other entrainment mechanism proposed to date.Indeed,our high spec-\u003cbr /\u003etral resolution slit-scan observations of Hαshow that the main jet component\u003cbr /\u003ehas a uniform radial velocity of \u003ci\u003eV\u003c/i\u003e\u003csmall\u003eLSR\u003c/small\u003e=-160km s\u003csup\u003e-1\u003c/sup\u003e(\u0026Delta;v=10km s\u003csup\u003e-1\u003c/sup\u003e)and\u003cbr /\u003edid not show the presence of slow Hα components( |\u003ci\u003eV\u003c/i\u003e\u003csmall\u003eLSR\u003c/small\u003e | \u0026le; 120km s-\u003csup\u003e1\u003c/sup\u003e)\u003cbr /\u003ealong the edges of the jets.Such slow Hα emission was reported in previous\u003cbr /\u003eobservations and was proposed to arise from turbulent boundary layers be-\u003cbr /\u003etween the main flow and the ambient gas. Our results indicate that Hα and\u003cbr /\u003e[NII] originate from the main jet component(i.e. the ejecta),and also from\u003cbr /\u003ebow shocks and Hα filaments,but not from turbulent mixing layers.\u003cbr /\u003e We also investigated the ionization fraction in the jets using the [NII] / Hα\u003cbr /\u003eflux ratio. In the case of HH46/47,the ratio is 0.2-0.5 in the main jet\u003cbr /\u003ecomponent and even higher in some other regions.Shock model calculations\u003cbr /\u003eshow that the ratio is sensitive to the ionization fraction of preshock gas if\u003cbr /\u003ethe shock velocity is less than l00 km s\u003csup\u003e-1\u003c/sup\u003e. The observed high ratio for HH\u003cbr /\u003e46/47 is expected if its main jet component is considerably ionized,although\u003cbr /\u003eprevious observations proposed a much lower ionization fraction of\u0026le;0.2.\u003cbr /\u003eThe [NII] / Hαflux ratio is significantly smaller than 0.2 in the one-side bow\u003cbr /\u003eshocks and Hα filaments, indicating that the gas surrounding the ejecta is\u003cbr /\u003erather neutral.\u003cbr /\u003e For the HL Tau jet,the observed [NII] / Hα flux ratio markedly vary from\u003cbr /\u003eone region to another: 0.1-0.7 at the base of the jet,less than 0.1 in knot\u003cbr /\u003eA,~0.2 in knot B,~0.4 in knot C,and ~0.7 in knot D.Because the shock\u003cbr/\u003evelocities of the HL Tau jet exceed 100 km s\u003csup\u003e-1\u003c/sup\u003e in some regions,the ratio\u003cbr /\u003edoes not directly reflect the ionization fraction of preshock gas. At the knots\u003cbr /\u003eA-D,the [NII] / Hαflux ratio increases from <0.1 to 0.7 with distance from\u003cbr /\u003ethe source. This suggests that the preshock density decreases with distance\u003cbr /\u003efrom the source.The ratio at the lateral of the bow shocks is less than\u003cbr /\u003e~0.1,suggesting that the ambient medium is almost neutral.At the base\u003cbr /\u003eof the jet,the observed [NII] / Hα flux ratio decreases from 0.7 to 0.1 as the\u003cbr /\u003edistance from the source increase. This suggests that the ionization fraction\u003cbr /\u003edecreases with distance as a result of radiative recombination.\u003cbr /\u003e We compared the [NII] / Hα ratio in the main jet components of the HH\u003cbr /\u003e46/47 jet and HL Tau jet. The ratio for the HH 46/47 jet is higher(0.2-0.5)\u003cbr /\u003ethan that for the HL Tau(\u0026le; 0.2),indicating high ionization fraction.Such\u003cbr /\u003ea difference suggests that the radiation from a nearby O star irradiates the\u003cbr /\u003eambient gas of the HH 46/47 system,which is located near the HII region\u003cbr /\u003eGum nebula,causing the high ionization fraction in the main jet component.\u003cbr /\u003eAnother possible interpretation is that radiative cooling by recombination is\u003cbr /\u003enot efficient in the HH 46/47 jet because of its low density,thus allowing the\u003cbr /\u003ehigh ionization fraction in the jet significantly away from the driving source.", "subitem_description_type": "Other"}]}, "item_1_description_18": {"attribute_name": "フォーマット", "attribute_value_mlt": [{"subitem_description": "application/pdf", "subitem_description_type": "Other"}]}, "item_1_description_7": {"attribute_name": "学位記番号", "attribute_value_mlt": [{"subitem_description": "総研大甲第1035号", "subitem_description_type": "Other"}]}, "item_1_select_14": {"attribute_name": "所蔵", "attribute_value_mlt": [{"subitem_select_item": "有"}]}, "item_1_select_8": {"attribute_name": "研究科", "attribute_value_mlt": [{"subitem_select_item": "物理科学研究科"}]}, "item_1_select_9": {"attribute_name": "専攻", "attribute_value_mlt": [{"subitem_select_item": "09 天文科学専攻"}]}, "item_1_text_10": {"attribute_name": "学位授与年度", "attribute_value_mlt": [{"subitem_text_value": "2006"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "NISHIKAWA, Takayuki", "creatorNameLang": "en"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_files": {"attribute_name": "ファイル情報", "attribute_type": "file", "attribute_value_mlt": [{"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 0, "filename": "甲1035_要旨.pdf", "filesize": [{"value": "382.0 kB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 382000.0, "url": {"label": "要旨・審査要旨", "url": "https://ir.soken.ac.jp/record/431/files/甲1035_要旨.pdf"}, "version_id": "241db0af-4181-4123-bb71-d6695aed5cd9"}, {"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 1, "filename": "甲1035_本文.pdf", "filesize": [{"value": "24.5 MB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 24500000.0, "url": {"label": "本文", "url": "https://ir.soken.ac.jp/record/431/files/甲1035_本文.pdf"}, "version_id": "147962ac-4eb9-4bbf-b037-149e7b57fa31"}]}, "item_language": {"attribute_name": "言語", "attribute_value_mlt": [{"subitem_language": "eng"}]}, "item_resource_type": {"attribute_name": "資源タイプ", "attribute_value_mlt": [{"resourcetype": "thesis", "resourceuri": "http://purl.org/coar/resource_type/c_46ec"}]}, "item_title": "Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects"}, {"subitem_title": "Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects", "subitem_title_language": "en"}]}, "item_type_id": "1", "owner": "1", "path": ["11"], "permalink_uri": "https://ir.soken.ac.jp/records/431", "pubdate": {"attribute_name": "公開日", "attribute_value": "2010-02-22"}, "publish_date": "2010-02-22", "publish_status": "0", "recid": "431", "relation": {}, "relation_version_is_last": true, "title": ["Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects"], "weko_shared_id": -1}
Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects
https://ir.soken.ac.jp/records/431
https://ir.soken.ac.jp/records/4318095a65e-e656-4c3e-a4d1-2b143de66b7e
名前 / ファイル | ライセンス | アクション |
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Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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公開日 | 2010-02-22 | |||||
タイトル | ||||||
タイトル | Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects | |||||
タイトル | ||||||
言語 | en | |||||
タイトル | Kinematic Structure and Ionization of Optical Jets Associated with Young Stellar Objects | |||||
言語 | ||||||
言語 | eng | |||||
資源タイプ | ||||||
資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
資源タイプ | thesis | |||||
著者名 |
西川, 貴行
× 西川, 貴行 |
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フリガナ |
ニシカワ, タカユキ
× ニシカワ, タカユキ |
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著者 |
NISHIKAWA, Takayuki
× NISHIKAWA, Takayuki |
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学位授与機関 | ||||||
学位授与機関名 | 総合研究大学院大学 | |||||
学位名 | ||||||
学位名 | 博士(理学) | |||||
学位記番号 | ||||||
内容記述タイプ | Other | |||||
内容記述 | 総研大甲第1035号 | |||||
研究科 | ||||||
値 | 物理科学研究科 | |||||
専攻 | ||||||
値 | 09 天文科学専攻 | |||||
学位授与年月日 | ||||||
学位授与年月日 | 2007-03-23 | |||||
学位授与年度 | ||||||
2006 | ||||||
要旨 | ||||||
内容記述タイプ | Other | |||||
内容記述 | Optical jets and molecular bipolar outflows are two major manifestations<br />of outflowing activities associated with young stellar objects (YSOs).It is<br />not clear how these two outflow activities are related with each other.One of<br />the major scenarios is that a collimated jet seen in the optical-IR wavelength<br />entrains its ambient molecular material,a1lowing the molecular outflow to<br />occur. In order for us to tackle this issue,it is crucial to understand how jets<br />interact with ambient material.<br /> In addition to the kinematics,the mass loss rate and mass momentum<br />transfer rate of are key parameters to investigate how the jet interacts<br />with the ambient material. However,the mass momentum is poorly known<br />because the hydrogen density is not easily derived, as is different from the<br />electron density that is measured from forbidden line emissions. If we assume<br />that a jet is fully ionized, i.e. the electron density is nearly equal to the<br />hydrogen density,the mass momentum of the jet derived from its optical<br />emission lines is not sufficient to drive the molecular outflow associated with<br />it. In contrast,recent studies have suggested that jets are almost neutral,<br />indicating that a jet may have momentum sufficient to drive a molecular outflow.<br /> In order to study the issues described above,we made slit-scan observa-<br />tions of Hα and [NII] 6583 Å emission lines toward two bright jets,HH46/47<br />and the HL Tau jet,with Subaru Telescope. The large diameter of the tele-<br />scope,together with the high spectral resolution of the spectrograph(High<br />Dispersion Spectrograph,R =3.6×10<sup>40</sup> or Δv=8km s<sup>-1</sup>)allowed us to<br />study the kinematics of these jets in unprecedented detail.Furthermore,the<br />slit-scan technique with a long slit provided us with kinematic information<br />of the entire jets.<br /> We found that,in both jets,the Hα emission traces both the main jet<br />component(<i>V</i><small>LSR</small>=-160~-180km s<sup>-1</sup>)and distinct lower velocity com-<br />ponent (|<i>V</i><small>LSR</small>| ≤ 120km s<sup>-1</sup>). The [NII] emission, on the other hand,is<br />primarily associated with the main jet component and is much faint or ab-<br />sent in the lower velocity component. In the HH 46/47 jet,the velocities<br />of Hαand [NII] emission lines match well in their main jet components.<br />The lower velocity components are associated with one-sided bow shocks<br />and with one of the Hα filaments that was previous identified with the<br /><i>Hubble Space Telescope.</i> In the HL Tau jet,the lower velocity component<br />is associated with indivisual knots, which is explained by the lower velocity<br />emmituion arising in the laterals of bow shocks. While the main jet component<br />is associated with the ejecta, the lower velocity component is produced as a<br />result of the interaction between the ejecta and the surrounding gas.<br /> Observed Hα line profiles suggest that the shock velocities at the bow<br />shocks and the Hα filament with respect to the ambient gas are 60-80km s<sup>-1</sup><br />and 120-130 km s<sup>-1</sup> for HH46/47 and HL Tau,respectively. These are<br />markedly smaller than the three dimensional(3-D)velocities of the jets(~300<br />km s<sup>-1</sup>). The discrepancy between the shock velocity and 3-D velocity is<br />explained if the ambient gas moves outward by~200km s<sup>-1.</sup>. The velocity<br />of the ambient gas measured in the HH46/47 jet is similar to those of HH<br />47A and 47D,giant bow shocks ahead of the observed region.<br /> Through detailed analysis,we concluded that the outward motion of the<br /> ambient gas is a result of prompt entrainment,i.e. a jet sweeps up ambient<br />material at its head by a large bow shock,but not of turbulent entrainment,<br />the other entrainment mechanism proposed to date.Indeed,our high spec-<br />tral resolution slit-scan observations of Hαshow that the main jet component<br />has a uniform radial velocity of <i>V</i><small>LSR</small>=-160km s<sup>-1</sup>(Δv=10km s<sup>-1</sup>)and<br />did not show the presence of slow Hα components( |<i>V</i><small>LSR</small> | ≤ 120km s-<sup>1</sup>)<br />along the edges of the jets.Such slow Hα emission was reported in previous<br />observations and was proposed to arise from turbulent boundary layers be-<br />tween the main flow and the ambient gas. Our results indicate that Hα and<br />[NII] originate from the main jet component(i.e. the ejecta),and also from<br />bow shocks and Hα filaments,but not from turbulent mixing layers.<br /> We also investigated the ionization fraction in the jets using the [NII] / Hα<br />flux ratio. In the case of HH46/47,the ratio is 0.2-0.5 in the main jet<br />component and even higher in some other regions.Shock model calculations<br />show that the ratio is sensitive to the ionization fraction of preshock gas if<br />the shock velocity is less than l00 km s<sup>-1</sup>. The observed high ratio for HH<br />46/47 is expected if its main jet component is considerably ionized,although<br />previous observations proposed a much lower ionization fraction of≤0.2.<br />The [NII] / Hαflux ratio is significantly smaller than 0.2 in the one-side bow<br />shocks and Hα filaments, indicating that the gas surrounding the ejecta is<br />rather neutral.<br /> For the HL Tau jet,the observed [NII] / Hα flux ratio markedly vary from<br />one region to another: 0.1-0.7 at the base of the jet,less than 0.1 in knot<br />A,~0.2 in knot B,~0.4 in knot C,and ~0.7 in knot D.Because the shock<br/>velocities of the HL Tau jet exceed 100 km s<sup>-1</sup> in some regions,the ratio<br />does not directly reflect the ionization fraction of preshock gas. At the knots<br />A-D,the [NII] / Hαflux ratio increases from <0.1 to 0.7 with distance from<br />the source. This suggests that the preshock density decreases with distance<br />from the source.The ratio at the lateral of the bow shocks is less than<br />~0.1,suggesting that the ambient medium is almost neutral.At the base<br />of the jet,the observed [NII] / Hα flux ratio decreases from 0.7 to 0.1 as the<br />distance from the source increase. This suggests that the ionization fraction<br />decreases with distance as a result of radiative recombination.<br /> We compared the [NII] / Hα ratio in the main jet components of the HH<br />46/47 jet and HL Tau jet. The ratio for the HH 46/47 jet is higher(0.2-0.5)<br />than that for the HL Tau(≤ 0.2),indicating high ionization fraction.Such<br />a difference suggests that the radiation from a nearby O star irradiates the<br />ambient gas of the HH 46/47 system,which is located near the HII region<br />Gum nebula,causing the high ionization fraction in the main jet component.<br />Another possible interpretation is that radiative cooling by recombination is<br />not efficient in the HH 46/47 jet because of its low density,thus allowing the<br />high ionization fraction in the jet significantly away from the driving source. | |||||
所蔵 | ||||||
値 | 有 | |||||
フォーマット | ||||||
内容記述タイプ | Other | |||||
内容記述 | application/pdf |