The diffuse continuum γ‐ray emission from the Galaxy provides a unique tracer of cosmic rays. The emission above ∼50 MeV is well studied by the SAS‐2 and COS‐B satellites and can soon be analyzed with better angular resolution and sensitivity now the all‐sky survey by the EGRET telescope aboard the Compton Observatory has been completed. Information for the 1–50 MeV range was far more limited prior to the launch of the Compton Observatory. The COMPTEL telescope on this observatory provides for the first time extensive imaging possibilities at MeV energies. This paper presents a global review of the diffuse gamma radiation between about 1 MeV and 10 GeV, with emphasis on implications for the low‐energy cosmic‐ray electron spectrum and the distribution of cosmic rays in the Galaxy. A complementary review on the diffuse emission below 1 MeV is given by R. Ramaty in this volume.
{"title":"Diffuse Galactic gamma‐ray emission above 1 MEV","authors":"H. Bloemen","doi":"10.1063/1.43960","DOIUrl":"https://doi.org/10.1063/1.43960","url":null,"abstract":"The diffuse continuum γ‐ray emission from the Galaxy provides a unique tracer of cosmic rays. The emission above ∼50 MeV is well studied by the SAS‐2 and COS‐B satellites and can soon be analyzed with better angular resolution and sensitivity now the all‐sky survey by the EGRET telescope aboard the Compton Observatory has been completed. Information for the 1–50 MeV range was far more limited prior to the launch of the Compton Observatory. The COMPTEL telescope on this observatory provides for the first time extensive imaging possibilities at MeV energies. This paper presents a global review of the diffuse gamma radiation between about 1 MeV and 10 GeV, with emphasis on implications for the low‐energy cosmic‐ray electron spectrum and the distribution of cosmic rays in the Galaxy. A complementary review on the diffuse emission below 1 MeV is given by R. Ramaty in this volume.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115441503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kahn and Woltjer (1959) assumed simple two‐body motion of M31 and our galaxy with initial recession and now approach of the two galaxies to estimate the total mass. However, recent measurements of recession speeds and distances of IC342 and Maffei 1 (Buta and McCall 1983, McCall 1989) indicate that each of these galaxies must once have been so close to M31 that there was a gravitational interaction stronger than with our galaxy, violating the two body assumption. We show with computer simulations and a generalized Kahn‐Woltjer calculation that a few‐body ejection/merger event involving M31 about 5⋅109 years ago can explain the present‐day distances and velocities of these galaxies. The smaller mass IC342 and Maffei were dynamically ejected rapidly away and the greater mass M31 slowly toward us in the opposite direction. In contrast, we find our galaxy to have been a ‘‘by‐stander’’ to these events. However, besides IC342 and Maffei 1, other much smaller mass objects undoubtedly were ejected, some toward our galaxy. One or more of these captured ejecta may confuse estimates of the mass of our galaxy using satellites. Looking toward the future, in about 10⋅109 years, our simulations predict a wide encounter with M31. Finally, although we find the initial assumption of Kahn‐Woltjer’s mass calculation of 4⋅1012 M⊙ for the Local Group invalid, we get a similar result with our generalized Kahn‐Woltjer method.Kahn and Woltjer (1959) assumed simple two‐body motion of M31 and our galaxy with initial recession and now approach of the two galaxies to estimate the total mass. However, recent measurements of recession speeds and distances of IC342 and Maffei 1 (Buta and McCall 1983, McCall 1989) indicate that each of these galaxies must once have been so close to M31 that there was a gravitational interaction stronger than with our galaxy, violating the two body assumption. We show with computer simulations and a generalized Kahn‐Woltjer calculation that a few‐body ejection/merger event involving M31 about 5⋅109 years ago can explain the present‐day distances and velocities of these galaxies. The smaller mass IC342 and Maffei were dynamically ejected rapidly away and the greater mass M31 slowly toward us in the opposite direction. In contrast, we find our galaxy to have been a ‘‘by‐stander’’ to these events. However, besides IC342 and Maffei 1, other much smaller mass objects undoubtedly were ejected, some toward ou...
Kahn和Woltjer(1959)假设M31和我们的星系有简单的两体运动，最初是衰退的，现在是两个星系的接近，以估计总质量。然而，最近对IC342和Maffei 1的衰退速度和距离的测量(Buta and McCall 1983, McCall 1989)表明，这些星系中的每一个都必须曾经如此接近M31，以至于引力相互作用比与我们的星系更强，这违反了两体假设。我们通过计算机模拟和广义Kahn - Woltjer计算表明，大约5⋅109年前涉及M31的几体抛射/合并事件可以解释这些星系目前的距离和速度。较小质量的IC342和Maffei被动态地快速弹射出去，而较大质量的M31则以相反的方向缓慢地向我们靠近。相反，我们发现我们的星系只是这些事件的“旁观者”。然而，除了IC342和玛菲1之外，其他质量小得多的天体无疑也被抛射出来，其中一些是向银河系抛射的。这些捕获的喷射物中的一个或多个可能会混淆使用卫星对银河系质量的估计。展望未来，在大约10⋅109年后，我们的模拟预测了与M31的大范围相遇。最后，虽然我们发现Kahn‐Woltjer的4⋅1012 M⊙的局部群质量计算的初始假设是无效的，但我们用我们的广义Kahn‐Woltjer方法得到了类似的结果。Kahn和Woltjer(1959)假设M31和我们的星系有简单的两体运动，最初是衰退的，现在是两个星系的接近，以估计总质量。然而，最近对IC342和Maffei 1的衰退速度和距离的测量(Buta and McCall 1983, McCall 1989)表明，这些星系中的每一个都必须曾经如此接近M31，以至于引力相互作用比与我们的星系更强，这违反了两体假设。我们通过计算机模拟和广义Kahn - Woltjer计算表明，大约5⋅109年前涉及M31的几体抛射/合并事件可以解释这些星系目前的距离和速度。较小质量的IC342和Maffei被动态地快速弹射出去，而较大质量的M31则以相反的方向缓慢地向我们靠近。相反，我们发现我们的星系只是这些事件的“旁观者”。然而，除了IC342和玛菲1之外，其他质量小得多的天体无疑也被抛出，其中一些朝着我们的方向……
{"title":"‘‘Back to the future’’ major dynamical events in the local group 15 billion B.C. to A.D. 15 billion","authors":"G. Byrd, M. Valtonen, M. McCall, K. Innanen","doi":"10.1063/1.43977","DOIUrl":"https://doi.org/10.1063/1.43977","url":null,"abstract":"Kahn and Woltjer (1959) assumed simple two‐body motion of M31 and our galaxy with initial recession and now approach of the two galaxies to estimate the total mass. However, recent measurements of recession speeds and distances of IC342 and Maffei 1 (Buta and McCall 1983, McCall 1989) indicate that each of these galaxies must once have been so close to M31 that there was a gravitational interaction stronger than with our galaxy, violating the two body assumption. We show with computer simulations and a generalized Kahn‐Woltjer calculation that a few‐body ejection/merger event involving M31 about 5⋅109 years ago can explain the present‐day distances and velocities of these galaxies. The smaller mass IC342 and Maffei were dynamically ejected rapidly away and the greater mass M31 slowly toward us in the opposite direction. In contrast, we find our galaxy to have been a ‘‘by‐stander’’ to these events. However, besides IC342 and Maffei 1, other much smaller mass objects undoubtedly were ejected, some toward our galaxy. One or more of these captured ejecta may confuse estimates of the mass of our galaxy using satellites. Looking toward the future, in about 10⋅109 years, our simulations predict a wide encounter with M31. Finally, although we find the initial assumption of Kahn‐Woltjer’s mass calculation of 4⋅1012 M⊙ for the Local Group invalid, we get a similar result with our generalized Kahn‐Woltjer method.Kahn and Woltjer (1959) assumed simple two‐body motion of M31 and our galaxy with initial recession and now approach of the two galaxies to estimate the total mass. However, recent measurements of recession speeds and distances of IC342 and Maffei 1 (Buta and McCall 1983, McCall 1989) indicate that each of these galaxies must once have been so close to M31 that there was a gravitational interaction stronger than with our galaxy, violating the two body assumption. We show with computer simulations and a generalized Kahn‐Woltjer calculation that a few‐body ejection/merger event involving M31 about 5⋅109 years ago can explain the present‐day distances and velocities of these galaxies. The smaller mass IC342 and Maffei were dynamically ejected rapidly away and the greater mass M31 slowly toward us in the opposite direction. In contrast, we find our galaxy to have been a ‘‘by‐stander’’ to these events. However, besides IC342 and Maffei 1, other much smaller mass objects undoubtedly were ejected, some toward ou...","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116323161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the rotation and proper motions of the bulge stars","authors":"HongSheng Zhao","doi":"10.1063/1.44017","DOIUrl":"https://doi.org/10.1063/1.44017","url":null,"abstract":"","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125293958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We summarize results of a measurement of the motion of the LSR with respect to anticenter carbon stars. New radial velocities were combined with existing K‐band photometry to examine the velocity mean and dispersion as a function of distance. The mean velocity of the carbon stars relative to the LSR is 6 km s−1 with a dispersion of 23 km s−1, and no trends with distance are evident. We conclude that the carbon star data are not consistent with the model proposed by Blitz and Spergel (1991), and tend to agree with the model of Kuijken (1991) more closely.
我们总结了LSR相对于反中心碳星运动的测量结果。新的径向速度与现有的K波段光度法相结合，研究了平均速度和色散作为距离的函数。碳星相对于LSR的平均速度为6 km s−1，色散为23 km s−1，且随距离的变化趋势不明显。我们认为碳星数据与Blitz和Spergel(1991)提出的模型并不一致，而更倾向于Kuijken(1991)的模型。
{"title":"Examining motion of the LSR using anticenter carbon stars","authors":"M. Metzger, P. Schechter","doi":"10.1063/1.43969","DOIUrl":"https://doi.org/10.1063/1.43969","url":null,"abstract":"We summarize results of a measurement of the motion of the LSR with respect to anticenter carbon stars. New radial velocities were combined with existing K‐band photometry to examine the velocity mean and dispersion as a function of distance. The mean velocity of the carbon stars relative to the LSR is 6 km s−1 with a dispersion of 23 km s−1, and no trends with distance are evident. We conclude that the carbon star data are not consistent with the model proposed by Blitz and Spergel (1991), and tend to agree with the model of Kuijken (1991) more closely.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117093752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of environment on the star formation process are currently not well understood. By studying the cloud populations in two different environments, spiral arms and the interarm regions, we hope to gain insight on the effects of environment in the star formation process. To this end, we are currently conducting a sensitive, 60‘ sampled survey of a one square degree region of the outer Galaxy in the J=1→0 transition of 12CO. Our survey region spans galactocentric radii between 9 and 16 kpc. Two populations of molecular clouds, arm and interarm, have been identified. The spiral arm population consists of GMC’s, with masses of 104 to 105 M⊙, and smaller clouds, clustered at velocities indicative of the 13 kpc spiral arm. The interarm clouds are dispersed throughout the remainder of the survey volume. The interarm population is comprised of small clouds with masses less than 104 M⊙.
{"title":"A sensitive survey in 12CO J=1→0 of arm and interarm molecular clouds in the outer Galaxy","authors":"S. Carey, M. Kutner, K. Mead","doi":"10.1063/1.43972","DOIUrl":"https://doi.org/10.1063/1.43972","url":null,"abstract":"The effects of environment on the star formation process are currently not well understood. By studying the cloud populations in two different environments, spiral arms and the interarm regions, we hope to gain insight on the effects of environment in the star formation process. To this end, we are currently conducting a sensitive, 60‘ sampled survey of a one square degree region of the outer Galaxy in the J=1→0 transition of 12CO. Our survey region spans galactocentric radii between 9 and 16 kpc. Two populations of molecular clouds, arm and interarm, have been identified. The spiral arm population consists of GMC’s, with masses of 104 to 105 M⊙, and smaller clouds, clustered at velocities indicative of the 13 kpc spiral arm. The interarm clouds are dispersed throughout the remainder of the survey volume. The interarm population is comprised of small clouds with masses less than 104 M⊙.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"278 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130261245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We use a modified particle‐mesh N‐body code, which can enhance the resolution of certain desirable regions to study the interaction between dark halo and its enclosed galaxy. We find that a transient rings with the nuclei displaced toward the edge of the ring can easily form if the center of the halo and the center of galaxy are separated by a distance d and move with a relative velocity υ. More intriguingly, these asymmetric rings can last up to a few billion years for some narrow parametric regimes of d and υ. An estimation of the probability of forming relatively stable asymmetric ring galaxies from our model are consistent with the observed results.
{"title":"Formation and origin of asymmetric ring galaxies","authors":"S. Leung, K. Cheng, W. Y. Chau, K. Chan","doi":"10.1063/1.43939","DOIUrl":"https://doi.org/10.1063/1.43939","url":null,"abstract":"We use a modified particle‐mesh N‐body code, which can enhance the resolution of certain desirable regions to study the interaction between dark halo and its enclosed galaxy. We find that a transient rings with the nuclei displaced toward the edge of the ring can easily form if the center of the halo and the center of galaxy are separated by a distance d and move with a relative velocity υ. More intriguingly, these asymmetric rings can last up to a few billion years for some narrow parametric regimes of d and υ. An estimation of the probability of forming relatively stable asymmetric ring galaxies from our model are consistent with the observed results.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131774704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Strong Magnetic Field Central Engine model (SMF) has been developed since 1961 to explain the variety of morphology and energetics of objects of galactic dimension. It is suggested that in the very center of our own Milky Way Galaxy, a newly discovered object, GZ‐A, is the remnant of our own weak central engine, but a prototype of those in far more energetic active galactic nuclei, such as in Seyferts and quasars.
{"title":"The strong magnetic field (SMF) central engine","authors":"H. Greyber","doi":"10.1063/1.43924","DOIUrl":"https://doi.org/10.1063/1.43924","url":null,"abstract":"The Strong Magnetic Field Central Engine model (SMF) has been developed since 1961 to explain the variety of morphology and energetics of objects of galactic dimension. It is suggested that in the very center of our own Milky Way Galaxy, a newly discovered object, GZ‐A, is the remnant of our own weak central engine, but a prototype of those in far more energetic active galactic nuclei, such as in Seyferts and quasars.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"109 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133132535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The anomalous component of cosmic rays comprises energetic particles which originate as neutral atoms in the Local Interstellar Medium (LISM). In 1991 it was discovered that these particles become trapped in the Earth’s magnetic field, with lifetimes which concentrate the particles to ∼500 times their interplanetary flux. This new ‘‘radiation belt’’ offers an opportunity for direct measurements of the isotopic composition of a number of elements from the LISM by a cosmic‐ray instrument in low‐Earth orbit. These measurements can be used to investigate how nucleosynthesis has evolved in the Galaxy and may offer clues to the circumstances surrounding the formation of the protosolar nebula.
{"title":"Anomalous cosmic rays and the local interstellar medium","authors":"J. Adams, A. Tylka","doi":"10.1063/1.44011","DOIUrl":"https://doi.org/10.1063/1.44011","url":null,"abstract":"The anomalous component of cosmic rays comprises energetic particles which originate as neutral atoms in the Local Interstellar Medium (LISM). In 1991 it was discovered that these particles become trapped in the Earth’s magnetic field, with lifetimes which concentrate the particles to ∼500 times their interplanetary flux. This new ‘‘radiation belt’’ offers an opportunity for direct measurements of the isotopic composition of a number of elements from the LISM by a cosmic‐ray instrument in low‐Earth orbit. These measurements can be used to investigate how nucleosynthesis has evolved in the Galaxy and may offer clues to the circumstances surrounding the formation of the protosolar nebula.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129543775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report the results of new analyses of far infrared spectral line observations from the FIRAS instrument on the COBE satellite with special attention to the spatial distributions of the 158 μm [C II] and the 122 μm and 205 μm [N II] emission lines. These distributions provide new insight into the large‐scale distribution and excitation of gas in the Milky Way. Transitions of [C I] at 370 μm and 609 μm and CO J=2‐1 through 5‐4 are also discussed.
{"title":"Cooling of the interstellar gas: results from COBE","authors":"C. Bennett, G. Hinshaw","doi":"10.1063/1.43984","DOIUrl":"https://doi.org/10.1063/1.43984","url":null,"abstract":"We report the results of new analyses of far infrared spectral line observations from the FIRAS instrument on the COBE satellite with special attention to the spatial distributions of the 158 μm [C II] and the 122 μm and 205 μm [N II] emission lines. These distributions provide new insight into the large‐scale distribution and excitation of gas in the Milky Way. Transitions of [C I] at 370 μm and 609 μm and CO J=2‐1 through 5‐4 are also discussed.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127150939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The 6.7 keV line is the K‐shell resonance transition from a Helium like iron (FeXXV) and is the most intense line in an optically thin cosmic plasma with a temperature ranging from 107 to 108 K. Therefore optically thin hot plasma in our Galaxy can be selected by the 6.7 keV line. This paper report on the 6.7 keV line map and discuss on the nature of the hot gas components in our Galaxy.
{"title":"X‐ray halo from the Galactic bulge ‐The 6.7 keV line mapping","authors":"K. Koyama, S. Yamauchi","doi":"10.1063/1.44016","DOIUrl":"https://doi.org/10.1063/1.44016","url":null,"abstract":"The 6.7 keV line is the K‐shell resonance transition from a Helium like iron (FeXXV) and is the most intense line in an optically thin cosmic plasma with a temperature ranging from 107 to 108 K. Therefore optically thin hot plasma in our Galaxy can be selected by the 6.7 keV line. This paper report on the 6.7 keV line map and discuss on the nature of the hot gas components in our Galaxy.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126881007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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