Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionized gas, we propose state‐selective photoionization of sulfur within neutral regions as a mechanism to explain the 1.5 power scaling between optical forbidden lines of N ii and S ii in M 82 and identify it with the 1.5 power scaling found between the far infrared emission lines of N ii and C ii associated with large scale structure of the Galaxy. While N ii emission can be attributed uniquely to ionized regions, C ii emission arises in neutral photodissociation regions as well. Boundaries between ionized and neutral regions are found to contribute significantly to the Galactic luminosity of both species. Forbidden line emission of ionized sulfur, it is suggested, similarly probes neutral photodissociation regions.
{"title":"Probes of the warm ionized medium in the disk of the Galaxy","authors":"S. Petuchowski, C. Bennett","doi":"10.1063/1.43990","DOIUrl":"https://doi.org/10.1063/1.43990","url":null,"abstract":"Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionized gas, we propose state‐selective photoionization of sulfur within neutral regions as a mechanism to explain the 1.5 power scaling between optical forbidden lines of N ii and S ii in M 82 and identify it with the 1.5 power scaling found between the far infrared emission lines of N ii and C ii associated with large scale structure of the Galaxy. While N ii emission can be attributed uniquely to ionized regions, C ii emission arises in neutral photodissociation regions as well. Boundaries between ionized and neutral regions are found to contribute significantly to the Galactic luminosity of both species. Forbidden line emission of ionized sulfur, it is suggested, similarly probes neutral photodissociation regions.","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":"128497444","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 have developed a full‐sky model of galactic microwave radiation at frequencies from 0.4 GHz to ≳50 GHz, with a resolution of ∼2°. The primary components are free‐free emission from ionized hydrogen and synchrotron emission from cosmic rays. (Dust emission is negligible in this frequency range.) A variety of data are used to estimate free‐free emission from HII: the galactic plane and adjacent regions come from continuum surveys near 2.7 GHz; emission at higher galactic latitudes is approximated by a cosecant law. The synchrotron component is extrapolated from sky‐survey data at 408 MHz. Both components vary with frequency. This model has been used to derive corrections for galactic emission in our measurements of the low‐frequency CMBR spectrum.
{"title":"Modeling galactic microwave emission from 0.4 to 50 GHz","authors":"C. Witebsky, G. Smoot, G. Amici, J. Aymon","doi":"10.1063/1.44015","DOIUrl":"https://doi.org/10.1063/1.44015","url":null,"abstract":"We have developed a full‐sky model of galactic microwave radiation at frequencies from 0.4 GHz to ≳50 GHz, with a resolution of ∼2°. The primary components are free‐free emission from ionized hydrogen and synchrotron emission from cosmic rays. (Dust emission is negligible in this frequency range.) A variety of data are used to estimate free‐free emission from HII: the galactic plane and adjacent regions come from continuum surveys near 2.7 GHz; emission at higher galactic latitudes is approximated by a cosecant law. The synchrotron component is extrapolated from sky‐survey data at 408 MHz. Both components vary with frequency. This model has been used to derive corrections for galactic emission in our measurements of the low‐frequency CMBR spectrum.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"38 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":"126815672","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 excitation of oscillation in the rotating disk of the Galactic center is considered. HII regions are usually thermally stable, because of the heating due to photoelectrons produced by ionizations of the UV radiation from central OB stars. The different point from the usual HII regions is that the Galactic center is the rotational HII region. The coupling between the rotational and non‐adiabatic effects brings the instabilities of nonradial oscillations in the HII region of the Galactic center. Hence, it is possible to say that the spiral and bar‐like structure is the trapped nonradial oscillations of gravity mode, excited by the heating of photoelectrons. Furthermore, the oscillation in the outer region surrounding the HII region is generated by the nonadiabatic resonance, where the epicyclic frequency is near to the Lamb frequency. This oscillation is expected to be the warp motion of the molecular ring.
{"title":"On the thermal instability around the boundary of H II region in the Galactic center","authors":"M. Kondo","doi":"10.1063/1.43940","DOIUrl":"https://doi.org/10.1063/1.43940","url":null,"abstract":"The excitation of oscillation in the rotating disk of the Galactic center is considered. HII regions are usually thermally stable, because of the heating due to photoelectrons produced by ionizations of the UV radiation from central OB stars. The different point from the usual HII regions is that the Galactic center is the rotational HII region. The coupling between the rotational and non‐adiabatic effects brings the instabilities of nonradial oscillations in the HII region of the Galactic center. Hence, it is possible to say that the spiral and bar‐like structure is the trapped nonradial oscillations of gravity mode, excited by the heating of photoelectrons. Furthermore, the oscillation in the outer region surrounding the HII region is generated by the nonadiabatic resonance, where the epicyclic frequency is near to the Lamb frequency. This oscillation is expected to be the warp motion of the molecular ring.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"31 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":"121707829","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 investigate the evolution of velocity dispersion of disk stars due to gravitational scattering by giant molecular clouds (GMCs) through numerical integration of orbits in a differentially rotating disk. We find that the evolution of the velocity dispersion can be divided into two phases. In the first phase where the velocity dispersion is small and the relative velocity to the GMC is determined by the shear velocity of the galactic disk, the radial and tangential components of the velocity dispersion increase with time as σR,σθ∝t1/2, while the vertical component as σz∝exp(t). In the later phase where the velocity dispersion becomes large enough to govern the relative velocity, all the components increase as σR,σθ,σz∝t1/4 and ratios among them converge to σR:σθ:σz≂1:0.7:0.6, independent of the initial conditions of velocity dispersion. These behaviors agree well with the observed velocity dispersion of disk stars with various ages.
{"title":"Velocity evolution of disk stars due to gravitational scattering by giant molecular clouds","authors":"E. Kokubo, S. Ida","doi":"10.1063/1.43955","DOIUrl":"https://doi.org/10.1063/1.43955","url":null,"abstract":"We investigate the evolution of velocity dispersion of disk stars due to gravitational scattering by giant molecular clouds (GMCs) through numerical integration of orbits in a differentially rotating disk. We find that the evolution of the velocity dispersion can be divided into two phases. In the first phase where the velocity dispersion is small and the relative velocity to the GMC is determined by the shear velocity of the galactic disk, the radial and tangential components of the velocity dispersion increase with time as σR,σθ∝t1/2, while the vertical component as σz∝exp(t). In the later phase where the velocity dispersion becomes large enough to govern the relative velocity, all the components increase as σR,σθ,σz∝t1/4 and ratios among them converge to σR:σθ:σz≂1:0.7:0.6, independent of the initial conditions of velocity dispersion. These behaviors agree well with the observed velocity dispersion of disk stars with various ages.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128221035","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":"The properties of the local bubble from EUV observations","authors":"R. Warwick, C. Barber, S. Hodgkin, J. Pye","doi":"10.1063/1.44008","DOIUrl":"https://doi.org/10.1063/1.44008","url":null,"abstract":"","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"25 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125893390","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}
Flat galactic rotation curves represent strong evidence that a substantial fraction of the total galactic gravitational mass is not visible or that gravitational dynamics on the galactic scale is not understood. Particle physics models do no offer any simple explanation as to why the dark matter candidates assume the requisite shape (e.g., a coronal halo), because the basic problem of galactic confinement is never addressed. A similar problem has existed in hadron physics until the advent of quantum chromodynamics and soliton bag theory. A new interpretation of the cosmological constant λ in general relativity as a confinement mechanism for the so‐called MIT bag (the author’s proposed tensor‐soliton theory of gravitation) is used to demonstrate that all hadronic matter in the Universe may be comprised of a hidden mass component due to λ.
{"title":"The cosmological constant and dark matter in the Galaxy","authors":"T. Wilson","doi":"10.1063/1.43944","DOIUrl":"https://doi.org/10.1063/1.43944","url":null,"abstract":"Flat galactic rotation curves represent strong evidence that a substantial fraction of the total galactic gravitational mass is not visible or that gravitational dynamics on the galactic scale is not understood. Particle physics models do no offer any simple explanation as to why the dark matter candidates assume the requisite shape (e.g., a coronal halo), because the basic problem of galactic confinement is never addressed. A similar problem has existed in hadron physics until the advent of quantum chromodynamics and soliton bag theory. A new interpretation of the cosmological constant λ in general relativity as a confinement mechanism for the so‐called MIT bag (the author’s proposed tensor‐soliton theory of gravitation) is used to demonstrate that all hadronic matter in the Universe may be comprised of a hidden mass component due to λ.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124795022","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 Leiden/Dwingeloo survey of galactic HI, which has occupied the 25‐meter telescope of the Netherlands Foundation for Research in Astronomy full‐time during the past 4 years, is now essentially complete. The new material provides 21‐cm coverage of the entire sky at δ≥−30° on a 0°.5 grid, over a velocity range of 1000 km s−1 at 1 km s−1 resolution. The Leiden/Dwingeloo data improve the 1974 (Heiles & Habing) Berkeley material by an order of magnitude in velocity coverage and in sensitivity; they improve the 1992 (Stark et al.) Bell Labs survey by about as much in spatial and kinematic coverage; and they extend the latitude coverage of the 1985 (Burton) Leiden/Green Bank survey of the northern Milky Way.
在过去的4年里，荷兰天文学研究基金会的25米望远镜一直被Leiden/Dwingeloo对银河系HI的调查所占据，现在基本上完成了。新材料在δ≥- 30°和0°上提供了整个天空21厘米的覆盖范围。5网格，速度范围为1000 km s−1，分辨率为1 km s−1。Leiden/Dwingeloo的数据在速度覆盖和灵敏度上提高了1974年(Heiles & Habing)伯克利材料的一个数量级;他们改进了1992年(斯塔克等人)贝尔实验室的调查，在空间和运动覆盖范围上大约相同;他们扩展了1985年莱顿/格林班克对北银河系的纬度覆盖范围。
{"title":"The Leiden/Dwingeloo survey of galactic HI at δ≥−30°","authors":"D. Hartmann, W. B. Burton","doi":"10.1063/1.43986","DOIUrl":"https://doi.org/10.1063/1.43986","url":null,"abstract":"The Leiden/Dwingeloo survey of galactic HI, which has occupied the 25‐meter telescope of the Netherlands Foundation for Research in Astronomy full‐time during the past 4 years, is now essentially complete. The new material provides 21‐cm coverage of the entire sky at δ≥−30° on a 0°.5 grid, over a velocity range of 1000 km s−1 at 1 km s−1 resolution. The Leiden/Dwingeloo data improve the 1974 (Heiles & Habing) Berkeley material by an order of magnitude in velocity coverage and in sensitivity; they improve the 1992 (Stark et al.) Bell Labs survey by about as much in spatial and kinematic coverage; and they extend the latitude coverage of the 1985 (Burton) Leiden/Green Bank survey of the northern Milky Way.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130028075","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}
S. Hunter, D. Bertsch, T. Dame, B. Dingus, C. Fichtel, R. Hartman, G. Kanbach, D. Kniffen, P. Kwok, Y. Lin, J. Mattox, H. Mayer-Hasselwander, P. Michelson, C. Montigny, P. Nolan, P. Sreekumar, P. Thaddeus, E. Schneid, G. Stacy, D. Thompson
One of the primary goals of the EGRET mission on the Compton Observatory has always been the study of the diffuse gamma ray emission of both galactic and extra‐galactic origin. The first 18 months of the mission, following the initial activation period, is being devoted to the all‐sky survey with the goal of obtaining a nearly uniform exposure. In anticipation of the improved capabilities of the EGRET instrument relative to the earlier SAS‐2 and COS‐B missions, a new model of the galactic diffuse gamma ray emission was developed that incorporates recent surveys of the matter distribution and which permits a variety of assumptions regarding galactic cosmic ray distribution to be tested. This paper summarizes the model calculation and gives a preliminary comparison of the model with EGRET observations.
{"title":"High energy gamma ray observations and the coupling between galactic cosmic rays and matter","authors":"S. Hunter, D. Bertsch, T. Dame, B. Dingus, C. Fichtel, R. Hartman, G. Kanbach, D. Kniffen, P. Kwok, Y. Lin, J. Mattox, H. Mayer-Hasselwander, P. Michelson, C. Montigny, P. Nolan, P. Sreekumar, P. Thaddeus, E. Schneid, G. Stacy, D. Thompson","doi":"10.1063/1.43962","DOIUrl":"https://doi.org/10.1063/1.43962","url":null,"abstract":"One of the primary goals of the EGRET mission on the Compton Observatory has always been the study of the diffuse gamma ray emission of both galactic and extra‐galactic origin. The first 18 months of the mission, following the initial activation period, is being devoted to the all‐sky survey with the goal of obtaining a nearly uniform exposure. In anticipation of the improved capabilities of the EGRET instrument relative to the earlier SAS‐2 and COS‐B missions, a new model of the galactic diffuse gamma ray emission was developed that incorporates recent surveys of the matter distribution and which permits a variety of assumptions regarding galactic cosmic ray distribution to be tested. This paper summarizes the model calculation and gives a preliminary comparison of the model with EGRET observations.","PeriodicalId":310353,"journal":{"name":"Back to the Galaxy","volume":"2010 29","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134480054","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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