Pub Date : 2000-11-01DOI: 10.1007/978-94-011-4778-1_159
J. Cernicharo
{"title":"Molecular Spectroscopy with ISO","authors":"J. Cernicharo","doi":"10.1007/978-94-011-4778-1_159","DOIUrl":"https://doi.org/10.1007/978-94-011-4778-1_159","url":null,"abstract":"","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132862436","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}
Pub Date : 2000-10-31DOI: 10.1017/S1539299600014696
T. Bedding
Asteroseismology involves using the resonant frequencies of a star to infer details about its internal structure and evolutionary state. Oscillation frequencies are most useful when accompanied by accurate measurements of the more traditional stellar parameters such as luminosity and effective temperature. The Hipparcos catalogue provides luminosities with precisions of a few percent or better for many oscillating stars. I briefly discuss the importance of Hipparcos measurements for interpreting asteroseismic data on three types of oscillating stars: delta Scuti variables, rapidly oscillating Ap stars and solar-like stars. I also retract the endorsement I made during my talk of Trimble's (1995) suggestion to change the spelling of "asteroseismology".
{"title":"Hipparcos luminosities and asteroseismology","authors":"T. Bedding","doi":"10.1017/S1539299600014696","DOIUrl":"https://doi.org/10.1017/S1539299600014696","url":null,"abstract":"Asteroseismology involves using the resonant frequencies of a star to infer details about its internal structure and evolutionary state. Oscillation frequencies are most useful when accompanied by accurate measurements of the more traditional stellar parameters such as luminosity and effective temperature. The Hipparcos catalogue provides luminosities with precisions of a few percent or better for many oscillating stars. I briefly discuss the importance of Hipparcos measurements for interpreting asteroseismic data on three types of oscillating stars: delta Scuti variables, rapidly oscillating Ap stars and solar-like stars. I also retract the endorsement I made during my talk of Trimble's (1995) suggestion to change the spelling of \"asteroseismology\".","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128723916","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}
Pub Date : 2000-10-26DOI: 10.1017/S1539299600014118
F. Bertoldi, K. Menten, E. Kreysa, C. Carilli, F. Owen
We discuss results from sensitive, wide-field imaging of the millimeter extragalactic background using the Max-Planck Millimeter Bolometer array (MAMBO) at the IRAM 30 m telescope.
{"title":"The Dawn of Galaxies: Deep MAMBO Imaging Surveys","authors":"F. Bertoldi, K. Menten, E. Kreysa, C. Carilli, F. Owen","doi":"10.1017/S1539299600014118","DOIUrl":"https://doi.org/10.1017/S1539299600014118","url":null,"abstract":"We discuss results from sensitive, wide-field imaging of the millimeter extragalactic background using the Max-Planck Millimeter Bolometer array (MAMBO) at the IRAM 30 m telescope.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130674598","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}
Pub Date : 2000-10-25DOI: 10.1017/S1539299600014726
Å. Nordlund, O. Rognvaldsson
We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using three-dimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching muG levels for reasonable values of the initial ratio of magnetic to thermal energy density.
{"title":"Magnetic Fields in Young Galaxies","authors":"Å. Nordlund, O. Rognvaldsson","doi":"10.1017/S1539299600014726","DOIUrl":"https://doi.org/10.1017/S1539299600014726","url":null,"abstract":"We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using three-dimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching muG levels for reasonable values of the initial ratio of magnetic to thermal energy density.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121653908","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}
Pub Date : 2000-10-24DOI: 10.1017/S1539299600014854
A. Brandenburg
Using a periodic box calculation it is shown that, owing to helicity conservation, a large scale field can only develop on a resistive timescale. This behaviour can be reproduced by a mean-field dynamo with alpha and eta_t quenchings that are equally strong and `catastrophic'.
{"title":"Numerical Simulations of Turbulent Dynamos","authors":"A. Brandenburg","doi":"10.1017/S1539299600014854","DOIUrl":"https://doi.org/10.1017/S1539299600014854","url":null,"abstract":"Using a periodic box calculation it is shown that, owing to helicity conservation, a large scale field can only develop on a resistive timescale. This behaviour can be reproduced by a mean-field dynamo with alpha and eta_t quenchings that are equally strong and `catastrophic'.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116786142","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}
Pub Date : 2000-10-15DOI: 10.1017/S1539299600014131
C. Carilli, K. Menten
We review observations of molecular absorption line systems at high redshift toward red quasars and gravitational lenses.
我们回顾了对红类星体和引力透镜的高红移分子吸收线系统的观测。
{"title":"Molecular QSO Absorption Line Systems","authors":"C. Carilli, K. Menten","doi":"10.1017/S1539299600014131","DOIUrl":"https://doi.org/10.1017/S1539299600014131","url":null,"abstract":"We review observations of molecular absorption line systems at high redshift toward red quasars and gravitational lenses.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131908813","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}
Pub Date : 2000-10-10DOI: 10.1017/S1539299600014684
L. Girardi
Variations of ~ 0.4 mag are expected in the I -band absolute magnitude of red clump giants, , as a function of both stellar age and metallicity. This is the case regardless of some potential theoretical uncertainties. The quite large differences in mean ages and metallicities of clump stars among galaxies result in systematic changes (of up to ~ 0.4 mag) in their . These numbers also indicate a distance to the LMC that is not necessarily “short”.
{"title":"Theoretical expectations for clump red giants as distance indicators","authors":"L. Girardi","doi":"10.1017/S1539299600014684","DOIUrl":"https://doi.org/10.1017/S1539299600014684","url":null,"abstract":"Variations of ~ 0.4 mag are expected in the I -band absolute magnitude of red clump giants, , as a function of both stellar age and metallicity. This is the case regardless of some potential theoretical uncertainties. The quite large differences in mean ages and metallicities of clump stars among galaxies result in systematic changes (of up to ~ 0.4 mag) in their . These numbers also indicate a distance to the LMC that is not necessarily “short”.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116590862","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}
Pub Date : 2000-09-29DOI: 10.1017/S1539299600014611
Anthony G. A. Brown
In the context of the luminosity calibration of the nearer stars I discuss the Hipparcos results on distances to nearby OB associations and open clusters. The shortcomings and assumptions in the analyses used to derive these results are pointed out and for the open clusters a comparison is made with results obtained from main sequence fitting. I conclude that given the considerable uncertainties in the latter technique there is no convincing evidence that the Hipparcos based distances to open clusters beyond the Hyades should not be trusted.
{"title":"OB Associations, Open Clusters, and the Luminosity Calibration of the Nearer Stars","authors":"Anthony G. A. Brown","doi":"10.1017/S1539299600014611","DOIUrl":"https://doi.org/10.1017/S1539299600014611","url":null,"abstract":"In the context of the luminosity calibration of the nearer stars I discuss the Hipparcos results on distances to nearby OB associations and open clusters. The shortcomings and assumptions in the analyses used to derive these results are pointed out and for the open clusters a comparison is made with results obtained from main sequence fitting. I conclude that given the considerable uncertainties in the latter technique there is no convincing evidence that the Hipparcos based distances to open clusters beyond the Hyades should not be trusted.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122925449","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}
Pub Date : 2000-08-30DOI: 10.1017/S1539299600014167
A. Blain
Observations made using COBE, SCUBA, ISO and MAMBO have provided a reasonable working knowledge of both the intensity of the submm and far-infrared background radiation and the source counts of luminous high-redshift dusty galaxies. However, because there are uncertainties in the background intensity determinations, the samples of detected galaxies are small, and most importantly, their redshift distributions are very incomplete, details of the evolution of dusty galaxies remain unresolved. The next steps forward in the field will be the launches of SIRTF and ASTRO-F, the commissioning of SOFIA and new, more capable ground-based mm/submm-wave cameras - BOLOCAM, SHARC-II and SCUBA-II - the use of ultra-long duration balloon experiments, such as BLAST, the construction of ALMA and the arrival of FIRST, and ultimately the advent of space-borne far-infrared interferometers, such as SPECS. There are also exciting prospects for direct mm/submm-wave CO-line redshift surveys using wide-band spectrographs. Using these new facilities, the number of high-redshift dusty galaxies known will be increased dramatically. Spectroscopy using SIRTF, SOFIA and FIRST will probe the astrophysical processes within these sources in detail, hopefully addressing the open question of the fraction of the counts and background radiation that is generated by the formation of high-mass stars and by active galactic nuclei (AGNs). The spatial and spectral structure of distant dusty galaxies will finally be resolved in detail using ALMA and SPECS.
{"title":"Prospects for Future Far-Infrared/Submillimeter Studies of the High-Redshift Universe","authors":"A. Blain","doi":"10.1017/S1539299600014167","DOIUrl":"https://doi.org/10.1017/S1539299600014167","url":null,"abstract":"Observations made using COBE, SCUBA, ISO and MAMBO have provided a reasonable working knowledge of both the intensity of the submm and far-infrared background radiation and the source counts of luminous high-redshift dusty galaxies. However, because there are uncertainties in the background intensity determinations, the samples of detected galaxies are small, and most importantly, their redshift distributions are very incomplete, details of the evolution of dusty galaxies remain unresolved. The next steps forward in the field will be the launches of SIRTF and ASTRO-F, the commissioning of SOFIA and new, more capable ground-based mm/submm-wave cameras - BOLOCAM, SHARC-II and SCUBA-II - the use of ultra-long duration balloon experiments, such as BLAST, the construction of ALMA and the arrival of FIRST, and ultimately the advent of space-borne far-infrared interferometers, such as SPECS. There are also exciting prospects for direct mm/submm-wave CO-line redshift surveys using wide-band spectrographs. Using these new facilities, the number of high-redshift dusty galaxies known will be increased dramatically. Spectroscopy using SIRTF, SOFIA and FIRST will probe the astrophysical processes within these sources in detail, hopefully addressing the open question of the fraction of the counts and background radiation that is generated by the formation of high-mass stars and by active galactic nuclei (AGNs). The spatial and spectral structure of distant dusty galaxies will finally be resolved in detail using ALMA and SPECS.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128337741","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}
Pub Date : 2000-05-01DOI: 10.1017/S1539299600018712
N. Mandzhavidze, R. Ramaty
We review recent results obtained from the analysis of the solar flare gamma ray line emission: (a) The gamma ray derived ambient elemental abundances show that the First Ionization Potential (FIP) effect already sets in at relatively low altitudes in the solar atmosphere. (b) The composition of the flare accelerated particles that produce the gamma rays exhibit heavy element and 3He abundance enhancements that are typical for impulsive flares. Unlike the solar energetic particle (SEP) observations in interplanetary space, the gamma ray method allows us to trace the time development of these enhancements. (c) Solar flare gamma ray spectroscopy provides the most direct measure of the abundances of the two very high FIP elements, He and Ne, in subcoronal regions leading to somewhat higher abundances than the generally accepted values. (d) The high intensities of the act lines observed from a number of flares imply a high (≳ 0.1) ambient He/H and/or accelerated α/p. (e) There are indications for the isotopic fractionation of He from the photosphere to corona that has important implications on the mechanism of solar wind acceleration, the protosolar deuterium abundance and Galactic chemical evolution.
{"title":"Gamma Rays from Solar Flares","authors":"N. Mandzhavidze, R. Ramaty","doi":"10.1017/S1539299600018712","DOIUrl":"https://doi.org/10.1017/S1539299600018712","url":null,"abstract":"We review recent results obtained from the analysis of the solar flare gamma ray line emission: (a) The gamma ray derived ambient elemental abundances show that the First Ionization Potential (FIP) effect already sets in at relatively low altitudes in the solar atmosphere. (b) The composition of the flare accelerated particles that produce the gamma rays exhibit heavy element and 3He abundance enhancements that are typical for impulsive flares. Unlike the solar energetic particle (SEP) observations in interplanetary space, the gamma ray method allows us to trace the time development of these enhancements. (c) Solar flare gamma ray spectroscopy provides the most direct measure of the abundances of the two very high FIP elements, He and Ne, in subcoronal regions leading to somewhat higher abundances than the generally accepted values. (d) The high intensities of the act lines observed from a number of flares imply a high (≳ 0.1) ambient He/H and/or accelerated α/p. (e) There are indications for the isotopic fractionation of He from the photosphere to corona that has important implications on the mechanism of solar wind acceleration, the protosolar deuterium abundance and Galactic chemical evolution.","PeriodicalId":422890,"journal":{"name":"Highlights of Astronomy","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125090845","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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