T. J. Sodroski, M. Hauser, E. Dwek, T. Kelsall, S. Moseley, R. Silverberg, N. Boggess, N. Odegard, J. Weiland, B. Franz
Observations from the COBE Diffuse Infrared Background Experiment (DIRBE) of the 140 and 240 μm emission from the Galactic plane region (‖b‖<10°) are analyzed. Assuming an isothermal dust distribution along each line of sight, maps of dust temperature, optical depth, and total far‐infrared (FIR) brightness are derived. These quantities are combined with available 12CO and HI data to produce maps of the gas‐to‐dust mass ratio and the FIR luminosity per hydrogen mass. The results differ from those of a similar analysis using IRAS 60 and 100 μm data (Sodroski et al. 1987), at least in part because emission from small, transiently heated grains does not contribute significantly at 140 or 240 μm.A linear correlation analysis is used to decompose the 140 and 240 μm maps into components associated with the neutral atomic (HI), molecular (H2), and extended low‐density ionized (HII) gas phases of the interstellar medium. From the resulting emission components the large‐scale physical conditions within each gas pha...
{"title":"Large‐scale physical conditions in the interstellar medium from DIRBE observations","authors":"T. J. Sodroski, M. Hauser, E. Dwek, T. Kelsall, S. Moseley, R. Silverberg, N. Boggess, N. Odegard, J. Weiland, B. Franz","doi":"10.1063/1.44035","DOIUrl":"https://doi.org/10.1063/1.44035","url":null,"abstract":"Observations from the COBE Diffuse Infrared Background Experiment (DIRBE) of the 140 and 240 μm emission from the Galactic plane region (‖b‖<10°) are analyzed. Assuming an isothermal dust distribution along each line of sight, maps of dust temperature, optical depth, and total far‐infrared (FIR) brightness are derived. These quantities are combined with available 12CO and HI data to produce maps of the gas‐to‐dust mass ratio and the FIR luminosity per hydrogen mass. The results differ from those of a similar analysis using IRAS 60 and 100 μm data (Sodroski et al. 1987), at least in part because emission from small, transiently heated grains does not contribute significantly at 140 or 240 μm.A linear correlation analysis is used to decompose the 140 and 240 μm maps into components associated with the neutral atomic (HI), molecular (H2), and extended low‐density ionized (HII) gas phases of the interstellar medium. From the resulting emission components the large‐scale physical conditions within each gas pha...","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"5 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":"127829099","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}
Letting yourself be nominated for a conference summary talk is considered by some to be a big mistake. It eliminates the possibility of making up the sleep lost at night, while partying, during the day, while sitting in the talks. It even forces you to look at all the poster papers.But at a meeting like this, with the wealth of observational data, it is definitely not a mistake: it was even worth missing some of the parties! My problem was to devise a way to be sufficiently selective so as to provide a reasonably coherent summary. I chose to emphasize the multitude of large‐scale maps presented at the meeting. Many are relevant to the ‘‘worm paradigm’’ (Sec. 2), and the recent γ‐ray and ROSAT results are relevant to the Hot Ionized Medium (Sec. 3). And finally, I was impressed by a number of well‐crafted smaller‐scale observations, which elucidate particular aspects of the interstellar medium (Sec. 4).
{"title":"This meeting: A biased observer’s view","authors":"C. Heiles","doi":"10.1063/1.43948","DOIUrl":"https://doi.org/10.1063/1.43948","url":null,"abstract":"Letting yourself be nominated for a conference summary talk is considered by some to be a big mistake. It eliminates the possibility of making up the sleep lost at night, while partying, during the day, while sitting in the talks. It even forces you to look at all the poster papers.But at a meeting like this, with the wealth of observational data, it is definitely not a mistake: it was even worth missing some of the parties! My problem was to devise a way to be sufficiently selective so as to provide a reasonably coherent summary. I chose to emphasize the multitude of large‐scale maps presented at the meeting. Many are relevant to the ‘‘worm paradigm’’ (Sec. 2), and the recent γ‐ray and ROSAT results are relevant to the Hot Ionized Medium (Sec. 3). And finally, I was impressed by a number of well‐crafted smaller‐scale observations, which elucidate particular aspects of the interstellar medium (Sec. 4).","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"29 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":"123247624","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}
U. Herbstmeier, P. Moritz, Justina Engelmann, J. Kerp, G. Westphalen
{"title":"New insights into the structure of the ISM provided by ROSAT","authors":"U. Herbstmeier, P. Moritz, Justina Engelmann, J. Kerp, G. Westphalen","doi":"10.1063/1.44007","DOIUrl":"https://doi.org/10.1063/1.44007","url":null,"abstract":"","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":"126851079","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 show that two significant anomalies in the kinematics of the Galaxy, viz. the low value of the axis ratio of the velocity ellipsoid of old stars in the solar neighborhood and the difference in apparent rotation curves between distant stars and HI gas, can be explained if the gravitational potential in the Galactic plane is elliptical. In the best‐fit model, the isopotential curves have an axis ratio of 0.92, roughly constant with radius, and the mean circular speed is 200 km s−1.
我们发现，如果银河系平面的引力势是椭圆的，则可以解释银河系运动学中的两个显著异常，即太阳附近老恒星的速度椭球轴比的低值和遥远恒星与HI气体之间的视旋转曲线的差异。在最佳拟合模型中，等势曲线的轴比为0.92，与半径大致恒定，平均圆周速度为200 km s−1。
{"title":"Is the Milky Way elliptical","authors":"K. Kuijken, S. Tremaine","doi":"10.1063/1.43938","DOIUrl":"https://doi.org/10.1063/1.43938","url":null,"abstract":"We show that two significant anomalies in the kinematics of the Galaxy, viz. the low value of the axis ratio of the velocity ellipsoid of old stars in the solar neighborhood and the difference in apparent rotation curves between distant stars and HI gas, can be explained if the gravitational potential in the Galactic plane is elliptical. In the best‐fit model, the isopotential curves have an axis ratio of 0.92, roughly constant with radius, and the mean circular speed is 200 km s−1.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"9 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":"115324337","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}
M. Ueno, T. Ichikawa, S. Sato, Y. Kasaba, Masanao Ito
We obtained a near infrared survey of the Galactic center at H and K’ bands and detected a ring‐like structure of the obscuration surrounding the Galactic nucleus. The survey was performed by a special purpose infrared camera, which was mounted on the University Hawaii’s 61 cm telescope atop Mauna Kea, Hawaii in June 1991. We present an infrared color map of the Galactic center, which clearly shows the distribution of the dust clouds. Even in near infrared wavelengths, the Galactic plane suffers heavy extinction by a number of dark patches. The darklane of the Galactic disk spreads within 2 degree along the Galactic equator, and whose extinction is typically 14 mag at visible wavelength.
{"title":"Near infrared survey of the central 12 square degree of the Galaxy","authors":"M. Ueno, T. Ichikawa, S. Sato, Y. Kasaba, Masanao Ito","doi":"10.1063/1.43949","DOIUrl":"https://doi.org/10.1063/1.43949","url":null,"abstract":"We obtained a near infrared survey of the Galactic center at H and K’ bands and detected a ring‐like structure of the obscuration surrounding the Galactic nucleus. The survey was performed by a special purpose infrared camera, which was mounted on the University Hawaii’s 61 cm telescope atop Mauna Kea, Hawaii in June 1991. We present an infrared color map of the Galactic center, which clearly shows the distribution of the dust clouds. Even in near infrared wavelengths, the Galactic plane suffers heavy extinction by a number of dark patches. The darklane of the Galactic disk spreads within 2 degree along the Galactic equator, and whose extinction is typically 14 mag at visible wavelength.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"222 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":"122913005","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}
Y. Doi, T. Nakagawa, Y. Yui, H. Okuda, H. Shibai, T. Nishimura, F. Low
The first detailed survey of the Cygnus X region in the far‐infrared [C ii] line is presented. Spatial distribution of the [C ii] emission correlates well with that of IR continuum, but not with that of CO molecular line emission. The total luminosity of the [C ii] line in this region amounts to 0.3% of the total IR luminosity. Under the assumption that atomic gas is the dominant source of the [C ii] emission, we find that the total atomic gas mass corresponds to ∼30% of the total molecular gas mass. The observed high [C ii] cooling efficiency is out of proportion to high dust color temperature, suggesting that the structure of interstellar clouds is better represented by clusters of many optically thin, small cloudlets, rather than a few lumps of large, optically thick clouds.
{"title":"Clumpy structure of interstellar clouds in the Cygnus X region","authors":"Y. Doi, T. Nakagawa, Y. Yui, H. Okuda, H. Shibai, T. Nishimura, F. Low","doi":"10.1063/1.44034","DOIUrl":"https://doi.org/10.1063/1.44034","url":null,"abstract":"The first detailed survey of the Cygnus X region in the far‐infrared [C ii] line is presented. Spatial distribution of the [C ii] emission correlates well with that of IR continuum, but not with that of CO molecular line emission. The total luminosity of the [C ii] line in this region amounts to 0.3% of the total IR luminosity. Under the assumption that atomic gas is the dominant source of the [C ii] emission, we find that the total atomic gas mass corresponds to ∼30% of the total molecular gas mass. The observed high [C ii] cooling efficiency is out of proportion to high dust color temperature, suggesting that the structure of interstellar clouds is better represented by clusters of many optically thin, small cloudlets, rather than a few lumps of large, optically thick clouds.","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":"129045552","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 Diffuse Infrared Background Experiment (DIRBE) on NASA’s Cosmic Background Explorer (COBE) satellite has obtained low‐angular resolution photometric maps of the full sky in ten broad spectral bands from 1.2 to 240 μm wavelength, and linear polarization maps at 1.2, 2.3, and 3.5 μm. These maps provide dramatic new views of the interplanetary dust cloud, integrated stellar light, and dust in the interstellar medium. An empirical function is used to separate the contribution from interplanetary dust, facilitating study of the stellar and interstellar emissions from the plane of the Milky Way. Initial results of such studies are presented in accompanying papers.
{"title":"COBE/DIRBE observations of infrared emission from stars and dust","authors":"M. Hauser","doi":"10.1063/1.44013","DOIUrl":"https://doi.org/10.1063/1.44013","url":null,"abstract":"The Diffuse Infrared Background Experiment (DIRBE) on NASA’s Cosmic Background Explorer (COBE) satellite has obtained low‐angular resolution photometric maps of the full sky in ten broad spectral bands from 1.2 to 240 μm wavelength, and linear polarization maps at 1.2, 2.3, and 3.5 μm. These maps provide dramatic new views of the interplanetary dust cloud, integrated stellar light, and dust in the interstellar medium. An empirical function is used to separate the contribution from interplanetary dust, facilitating study of the stellar and interstellar emissions from the plane of the Milky Way. Initial results of such studies are presented in accompanying papers.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"6 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":"127469953","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}
Observations of positron electron annihilation radiation address some fundamental problems in Galactic astrophysics, including nucleosynthesis, supernovae, black holes, and the interstellar medium. The 0.511 MeV line resulting from positron annihilation is superposed on a continuum which probably is, in large part, bremsstrahlung of cosmic ray electrons. The power deposited by these electrons could have important implications for the interstellar medium.
{"title":"Diffuse <1 MEV Galactic gamma rays","authors":"R. Ramaty, J. Skibo","doi":"10.1063/1.43958","DOIUrl":"https://doi.org/10.1063/1.43958","url":null,"abstract":"Observations of positron electron annihilation radiation address some fundamental problems in Galactic astrophysics, including nucleosynthesis, supernovae, black holes, and the interstellar medium. The 0.511 MeV line resulting from positron annihilation is superposed on a continuum which probably is, in large part, bremsstrahlung of cosmic ray electrons. The power deposited by these electrons could have important implications for the interstellar medium.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"47 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":"128264924","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 projection of computer generated fractal clouds are examined. Systematic effects depending mainly on the fractal dimension of the ISM may lead to large underestimates of the mass contained in cold gas. The constant ratio of dark mass to estimated HI mass observed in the outer galactic disks (Bosma 1981) might be attributed principally to this geometric effect.
{"title":"Fractal geometry of interstellar gas and dark matter in HI disks","authors":"D. Pfenniger","doi":"10.1063/1.43943","DOIUrl":"https://doi.org/10.1063/1.43943","url":null,"abstract":"The projection of computer generated fractal clouds are examined. Systematic effects depending mainly on the fractal dimension of the ISM may lead to large underestimates of the mass contained in cold gas. The constant ratio of dark mass to estimated HI mass observed in the outer galactic disks (Bosma 1981) might be attributed principally to this geometric effect.","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":"131129451","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}
A wide‐spread belief in a ∼106 M⊙ mass for a putative black hole at the Galactic center is based on the approaches which employ the gravitational field of a point mass at such large distances that the contributions of any distributed matter is not negligible, and therefore the figure above cannot be considered as a reliable one. A method used in the present work employs the radiation spectrum of the black hole, i.e., it is based on a local approach. Approximate analytical expressions are obtained to estimate the mass of the black hole from its spectral luminosity assumed to result from the Bondi accretion of the wind from a nearby group of hot massive stars, IRS 16. To fit the radio spectrum of Sgr A*, Mbh≂5⋅102 M⊙ is required; a 106 M⊙ black hole would result in an electron temperature only marginally relativistic, which is incompatible with the observed (synchrotron) spectrum. A comparatively low value for the black hole mass is consistent with the upper limits to Sgr A* mass found earlier.
{"title":"Evaluating the mass of a putative black hole at the Galactic center","authors":"L. Ozernoy","doi":"10.1063/1.43951","DOIUrl":"https://doi.org/10.1063/1.43951","url":null,"abstract":"A wide‐spread belief in a ∼106 M⊙ mass for a putative black hole at the Galactic center is based on the approaches which employ the gravitational field of a point mass at such large distances that the contributions of any distributed matter is not negligible, and therefore the figure above cannot be considered as a reliable one. A method used in the present work employs the radiation spectrum of the black hole, i.e., it is based on a local approach. Approximate analytical expressions are obtained to estimate the mass of the black hole from its spectral luminosity assumed to result from the Bondi accretion of the wind from a nearby group of hot massive stars, IRS 16. To fit the radio spectrum of Sgr A*, Mbh≂5⋅102 M⊙ is required; a 106 M⊙ black hole would result in an electron temperature only marginally relativistic, which is incompatible with the observed (synchrotron) spectrum. A comparatively low value for the black hole mass is consistent with the upper limits to Sgr A* mass found earlier.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"1 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":"130506564","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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