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Max Pettini - One of the best experts on this subject based on the ideXlab platform.
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a library of theoretical Ultraviolet Spectra of massive hot stars for evolutionary synthesis
Astrophysical Journal Supplement Series, 2010Co-Authors: Claus Leitherer, Paula Ortiz A Otalvaro, Fabio Bresolin, R P Kudritzki, Barbara Lo Faro, A W A Pauldrach, Max Pettini, Samantha A RixAbstract:We computed a comprehensive set of theoretical Ultraviolet Spectra of hot, massive stars with the radiation-hydrodynamics code WM-Basic. This model atmosphere and Spectral synthesis code is optimized for computing the strong P Cygni type lines originating in the winds of hot stars, which are the strongest features in the Ultraviolet Spectral region. The computed set is suitable as a Spectral library for inclusion in evolutionary synthesis models of star clusters and star-forming galaxies. The chosen stellar parameters cover the upper left Hertzsprung-Russell diagram at L 102.75 L ? and T eff 20,000 K. The adopted elemental abundances are 0.05 Z ?, 0.2 Z ?, 0.4 Z ?, Z ?, and 2 Z ?. The Spectra cover the wavelength range from 900 to 3000 ? and have a resolution of 0.4 ?. We compared the theoretical Spectra to data of individual hot stars in the Galaxy and the Magellanic Clouds obtained with the International Ultraviolet Explorer and Far Ultraviolet Spectroscopic Explorer satellites and found very good agreement. We built a library with the set of Spectra and implemented it into the evolutionary synthesis code Starburst99 where it complements and extends the existing empirical library toward lower chemical abundances. Comparison of population synthesis models at solar and near-solar composition demonstrates consistency between synthetic Spectra generated with either library. We discuss the potential of the new library for the interpretation of the rest-frame Ultraviolet Spectra of star-forming galaxies. Properties that can be addressed with the models include ages, initial mass function, and heavy-element abundance. The library can be obtained both individually or as part of the Starburst99 package.
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a library of theoretical Ultraviolet Spectra of massive hot stars for evolutionary synthesis
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: Claus Leitherer, Paula Ortiz A Otalvaro, Fabio Bresolin, R P Kudritzki, Barbara Lo Faro, A W A Pauldrach, Max Pettini, Samantha A RixAbstract:We computed a comprehensive set of theoretical Ultraviolet Spectra of hot, massive stars with the radiation-hydrodynamics code WM-Basic. This model atmosphere and Spectral synthesis code is optimized for computing the strong P Cygni-type lines originating in the winds of hot stars, which are the strongest features in the Ultraviolet Spectral region. The computed set is suitable as a Spectral library for inclusion in evolutionary synthesis models of star clusters and star-forming galaxies. The chosen stellar parameters cover the upper left Hertzsprung-Russell diagram at L >~ 10^2.75 Lsun and T_eff >~ 20,000 K. The adopted elemental abundances are 0.05 Zsun, 0.2 Zsun, 0.4 Zsun, Zsun, and 2 Zsun. The Spectra cover the wavelength range from 900 to 3000 {\AA} and have a resolution of 0.4 {\AA}. We compared the theoretical Spectra to data of individual hot stars in the Galaxy and the Magellanic Clouds obtained with the International Ultraviolet Explorer (IUE) and Far Ultraviolet Spectroscopic Explorer (FUSE) satellites and found very good agreement. We built a library with the set of Spectra and implemented it into the evolutionary synthesis code Starburst99 where it complements and extends the existing empirical library towards lower chemical abundances. Comparison of population synthesis models at solar and near-solar composition demonstrates consistency between synthetic Spectra generated with either library. We discuss the potential of the new library for the interpretation of the rest-frame Ultraviolet Spectra of star-forming galaxies. Properties that can be addressed with the models include ages, initial mass function, and heavy-element abundance. The library can be obtained both individually or as part of the Starburst99 package.
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rest frame Ultraviolet Spectra of z 3 lyman break galaxies
The Astrophysical Journal, 2003Co-Authors: Alice E Shapley, Max Pettini, Charles C Steidel, Kurt L AdelbergerAbstract:We present the results of a systematic study of the rest-frame UV spectroscopic properties of Lyman break galaxies (LBGs). The database of almost 1000 LBG Spectra proves useful for constructing high signal-to-noise composite Spectra. The composite spectrum of the entire sample reveals a wealth of features attributable to hot stars, H II regions, dust, and outflowing neutral and ionized gas. By grouping the database according to galaxy parameters such as Lyα equivalent width, UV Spectral slope, and interstellar kinematics, we isolate some of the major trends in LBG Spectra that are least compromised by selection effects. We find that LBGs with stronger Lyα emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Lyα and the interstellar absorption lines, and lower star formation rates. There is a decoupling between the dependence of low- and high-ionization outflow features on other Spectral properties. Additionally, galaxies with rest-frame WLyα ≥ 20 A in emission have weaker than average high-ionization lines and nebular emission lines that are significantly stronger than in the sample as a whole. Most of the above trends can be explained in terms of the properties of the large-scale outflows seen in LBGs. According to this scenario, the appearance of LBG Spectra is determined by a combination of the covering fraction of outflowing neutral gas, which contains dust and the range of velocities over which this gas is absorbing. In contrast, the strengths of collisionally excited nebular emission lines should not be affected by the nature of the outflow, and variations in these lines may indicate differences in the temperatures and metallicities in H II regions of galaxies with very strong Lyα emission. Higher sensitivity and Spectral resolution observations are still required for a full understanding of the covering fraction and velocity dispersion of the outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z ~ 3.
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rest frame Ultraviolet Spectra of z 3 lyman break galaxies
arXiv: Astrophysics, 2003Co-Authors: Alice E Shapley, Max Pettini, Charles C Steidel, Kurt L AdelbergerAbstract:We present the results of a systematic study of the rest-frame UV spectroscopic properties of Lyman Break Galaxies (LBGs). The database of almost 1000 LBG Spectra proves useful for constructing high S/N composite Spectra. The composite spectrum of the entire sample reveals a wealth of features attributable to hot stars, HII regions, dust, and outflowing neutral and ionized gas. By grouping the database according to galaxy parameters such as Lyman-alpha equivalent width, UV Spectral slope, and interstellar kinematics, we isolate some of the major trends in LBG Spectra which are least compromised by selection effects. We find that LBGs with stronger Lyman-alpha emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Lyman-alpha and the interstellar absorption lines, and lower star-formation rates. There is a decoupling between the dependence of low- and high-ionization outflow features on other Spectral properties. Most of the above trends can be explained in terms of the properties of the large-scale outflows seen in LBGs. According to this scenario, the appearance of LBG Spectra is determined by a combination of the covering fraction of outflowing neutral gas which contains dust, and the range of velocities over which this gas is absorbing. Higher sensitivity and Spectral resolution observations are still required for a full understanding of the covering fraction and velocity dispersion of the outflowing neutral gas in LBGs, and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z~3.
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Ultraviolet line Spectra of metal poor star forming galaxies
The Astrophysical Journal, 2001Co-Authors: Claus Leitherer, Max Pettini, Joao R S Leao, Timothy M Heckman, D J Lennon, Carmelle RobertAbstract:We present synthetic Ultraviolet Spectra of metal-poor star-forming galaxies that were calculated with the Starburst99 package. A new Spectral library was generated from Hubble Space Telescope observations of O stars in the Large and Small Magellanic Clouds. The corresponding mean metallicity of the synthetic Spectra is approximately The Spectra have a resolution of 1 and cover the Spectral 1 Z _ .A e range 1200¨1600 A set of model Spectra was calculated for a standard initial mass function and star Ae . formation history and is compared to synthetic Spectra at solar metallicity. We —nd that the Spectral lines are generally weaker at lower metallicity, as expected from the lower elemental abundances. Stellar wind lines, however, show a more complex behavior: the metallicity dependence of the ionization balance can be important in trace ions, like N4‘ and Si3‘. Therefore, the strength of N V j1240 and Si IV j1400 does not scale monotonically with metallicity. We compare our new models to Ultraviolet Spectra of NGC 5253 and MS 1512-cB58, two star-forming galaxies with one-fourth solar metallicity at low and high redshifts, respectively. The new library provides signi—cantly better —ts to the observations than earlier models using the library. We discuss the potential of utilizing stellar photospheric and Z _ wind lines to estimate the chemical composition of star-forming galaxies. The new metal-poor synthetic Spectra are available via the Starburst99 Web site.
Robert P Kirshner - One of the best experts on this subject based on the ideXlab platform.
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metallicity differences in type ia supernova progenitors inferred from Ultraviolet Spectra
The Astrophysical Journal, 2013Co-Authors: R J Foley, Robert P KirshnerAbstract:Two ''twin'' Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and Spectra, yet have different Ultraviolet (UV) continua as measured in Hubble Space Telescope Spectra and measurably different peak luminosities. We attribute the difference in the UV continua to significantly different progenitor metallicities. This is the first robust detection of different metallicities for SN Ia progenitors. Theoretical reasoning suggests that differences in metallicity also lead to differences in luminosity. SNe Ia with higher progenitor metallicities have lower {sup 56}Ni yields and lower luminosities for the same light-curve shape. SNe 2011by and 2011fe have different peak luminosities ({Delta}M{sub V} Almost-Equal-To 0.6 mag), which correspond to different {sup 56}Ni yields: M{sub 11fe}({sup 56}Ni) / M{sub 11by}({sup 56}Ni) = 1.7{sup +0.7}{sub -0.5}. From theoretical models that account for different neutron-to-proton ratios in progenitors, the differences in {sup 56}Ni yields for SNe 2011by and 2011fe imply that their progenitor stars were above and below solar metallicity, respectively. Although we can distinguish progenitor metallicities in a qualitative way from UV data, the quantitative interpretation in terms of abundances is limited by the present state of theoretical models.
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metallicity differences in type ia supernova progenitors inferred from Ultraviolet Spectra
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: R J Foley, Robert P KirshnerAbstract:Two "twin" Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and Spectra, yet have different Ultraviolet (UV) continua as measured in Hubble Space Telescope Spectra and measurably different peak luminosities. We attribute the difference in the UV continua to significantly different progenitor metallicities. This is the first robust detection of different metallicities for SN Ia progenitors. Theoretical reasoning suggests that differences in metallicity also lead to differences in luminosity. SNe Ia with higher progenitor metallicities have lower 56Ni yields, and lower luminosities, for the same light-curve shape. SNe 2011by and 2011fe have different peak luminosities (Delta M_V = 0.6 mag), which correspond to different 56Ni yields: M_11fe(56Ni)/M_11by(56Ni) = 1.7^+0.7_-0.5. From theoretical models that account for different neutron to proton ratios in progenitors, the differences in 56Ni yields for SNe 2011by and 2011fe imply that their progenitor stars were above and below solar metallicity, respectively. Although we can distinguish progenitor metallicities in a qualitative way from UV data, the quantitative interpretation in terms of abundances is limited by the present state of theoretical models.
Claus Leitherer - One of the best experts on this subject based on the ideXlab platform.
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a library of theoretical Ultraviolet Spectra of massive hot stars for evolutionary synthesis
Astrophysical Journal Supplement Series, 2010Co-Authors: Claus Leitherer, Paula Ortiz A Otalvaro, Fabio Bresolin, R P Kudritzki, Barbara Lo Faro, A W A Pauldrach, Max Pettini, Samantha A RixAbstract:We computed a comprehensive set of theoretical Ultraviolet Spectra of hot, massive stars with the radiation-hydrodynamics code WM-Basic. This model atmosphere and Spectral synthesis code is optimized for computing the strong P Cygni type lines originating in the winds of hot stars, which are the strongest features in the Ultraviolet Spectral region. The computed set is suitable as a Spectral library for inclusion in evolutionary synthesis models of star clusters and star-forming galaxies. The chosen stellar parameters cover the upper left Hertzsprung-Russell diagram at L 102.75 L ? and T eff 20,000 K. The adopted elemental abundances are 0.05 Z ?, 0.2 Z ?, 0.4 Z ?, Z ?, and 2 Z ?. The Spectra cover the wavelength range from 900 to 3000 ? and have a resolution of 0.4 ?. We compared the theoretical Spectra to data of individual hot stars in the Galaxy and the Magellanic Clouds obtained with the International Ultraviolet Explorer and Far Ultraviolet Spectroscopic Explorer satellites and found very good agreement. We built a library with the set of Spectra and implemented it into the evolutionary synthesis code Starburst99 where it complements and extends the existing empirical library toward lower chemical abundances. Comparison of population synthesis models at solar and near-solar composition demonstrates consistency between synthetic Spectra generated with either library. We discuss the potential of the new library for the interpretation of the rest-frame Ultraviolet Spectra of star-forming galaxies. Properties that can be addressed with the models include ages, initial mass function, and heavy-element abundance. The library can be obtained both individually or as part of the Starburst99 package.
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a library of theoretical Ultraviolet Spectra of massive hot stars for evolutionary synthesis
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: Claus Leitherer, Paula Ortiz A Otalvaro, Fabio Bresolin, R P Kudritzki, Barbara Lo Faro, A W A Pauldrach, Max Pettini, Samantha A RixAbstract:We computed a comprehensive set of theoretical Ultraviolet Spectra of hot, massive stars with the radiation-hydrodynamics code WM-Basic. This model atmosphere and Spectral synthesis code is optimized for computing the strong P Cygni-type lines originating in the winds of hot stars, which are the strongest features in the Ultraviolet Spectral region. The computed set is suitable as a Spectral library for inclusion in evolutionary synthesis models of star clusters and star-forming galaxies. The chosen stellar parameters cover the upper left Hertzsprung-Russell diagram at L >~ 10^2.75 Lsun and T_eff >~ 20,000 K. The adopted elemental abundances are 0.05 Zsun, 0.2 Zsun, 0.4 Zsun, Zsun, and 2 Zsun. The Spectra cover the wavelength range from 900 to 3000 {\AA} and have a resolution of 0.4 {\AA}. We compared the theoretical Spectra to data of individual hot stars in the Galaxy and the Magellanic Clouds obtained with the International Ultraviolet Explorer (IUE) and Far Ultraviolet Spectroscopic Explorer (FUSE) satellites and found very good agreement. We built a library with the set of Spectra and implemented it into the evolutionary synthesis code Starburst99 where it complements and extends the existing empirical library towards lower chemical abundances. Comparison of population synthesis models at solar and near-solar composition demonstrates consistency between synthetic Spectra generated with either library. We discuss the potential of the new library for the interpretation of the rest-frame Ultraviolet Spectra of star-forming galaxies. Properties that can be addressed with the models include ages, initial mass function, and heavy-element abundance. The library can be obtained both individually or as part of the Starburst99 package.
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Ultraviolet line Spectra of metal poor star forming galaxies
The Astrophysical Journal, 2001Co-Authors: Claus Leitherer, Max Pettini, Joao R S Leao, Timothy M Heckman, D J Lennon, Carmelle RobertAbstract:We present synthetic Ultraviolet Spectra of metal-poor star-forming galaxies that were calculated with the Starburst99 package. A new Spectral library was generated from Hubble Space Telescope observations of O stars in the Large and Small Magellanic Clouds. The corresponding mean metallicity of the synthetic Spectra is approximately The Spectra have a resolution of 1 and cover the Spectral 1 Z _ .A e range 1200¨1600 A set of model Spectra was calculated for a standard initial mass function and star Ae . formation history and is compared to synthetic Spectra at solar metallicity. We —nd that the Spectral lines are generally weaker at lower metallicity, as expected from the lower elemental abundances. Stellar wind lines, however, show a more complex behavior: the metallicity dependence of the ionization balance can be important in trace ions, like N4‘ and Si3‘. Therefore, the strength of N V j1240 and Si IV j1400 does not scale monotonically with metallicity. We compare our new models to Ultraviolet Spectra of NGC 5253 and MS 1512-cB58, two star-forming galaxies with one-fourth solar metallicity at low and high redshifts, respectively. The new library provides signi—cantly better —ts to the observations than earlier models using the library. We discuss the potential of utilizing stellar photospheric and Z _ wind lines to estimate the chemical composition of star-forming galaxies. The new metal-poor synthetic Spectra are available via the Starburst99 Web site.
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Ultraviolet line Spectra of metal poor star forming galaxies
arXiv: Astrophysics, 2000Co-Authors: Claus Leitherer, Max Pettini, Joao R S Leao, Timothy M Heckman, D J Lennon, Carmelle RobertAbstract:We present synthetic Ultraviolet Spectra of metal-poor star-forming galaxies which were calculated with the Starburst99 package. A new Spectral library was generated from HST observations of O stars in the Large and Small Magellanic Clouds. The corresponding mean metallicity of the synthetic Spectra is approximately 1/4\Zs. The Spectra have a resolution of 1\AA and cover the Spectral range 1200-1600\AA. A set of model Spectra was calculated for a standard initial mass function and star-formation history and is compared to synthetic Spectra at solar metallicity. We find that the Spectral lines are generally weaker at lower metallicity, as expected from the lower elemental abundances. Stellar-wind lines, however, show a more complex behavior: the metallicity dependence of the ionization balance can be important in trace ions, like N$^{4+}$ and Si$^{3+}$. Therefore the strength of \nv and \siiv does not scale monotonically with metallicity. We compare our new models to Ultraviolet Spectra of NGC 5253 and \cB, two star-forming galaxies with 1/4 solar metallicity at low and high redshift, respectively. The new library provides significantly better fits to the observations than earlier models using the \Zs library. We discuss the potential of utilizing stellar photospheric and wind lines to estimate the chemical composition of star-forming galaxies. The new metal-poor synthetic Spectra are available via the Starburst99 website.
R J Foley - One of the best experts on this subject based on the ideXlab platform.
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metallicity differences in type ia supernova progenitors inferred from Ultraviolet Spectra
The Astrophysical Journal, 2013Co-Authors: R J Foley, Robert P KirshnerAbstract:Two ''twin'' Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and Spectra, yet have different Ultraviolet (UV) continua as measured in Hubble Space Telescope Spectra and measurably different peak luminosities. We attribute the difference in the UV continua to significantly different progenitor metallicities. This is the first robust detection of different metallicities for SN Ia progenitors. Theoretical reasoning suggests that differences in metallicity also lead to differences in luminosity. SNe Ia with higher progenitor metallicities have lower {sup 56}Ni yields and lower luminosities for the same light-curve shape. SNe 2011by and 2011fe have different peak luminosities ({Delta}M{sub V} Almost-Equal-To 0.6 mag), which correspond to different {sup 56}Ni yields: M{sub 11fe}({sup 56}Ni) / M{sub 11by}({sup 56}Ni) = 1.7{sup +0.7}{sub -0.5}. From theoretical models that account for different neutron-to-proton ratios in progenitors, the differences in {sup 56}Ni yields for SNe 2011by and 2011fe imply that their progenitor stars were above and below solar metallicity, respectively. Although we can distinguish progenitor metallicities in a qualitative way from UV data, the quantitative interpretation in terms of abundances is limited by the present state of theoretical models.
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metallicity differences in type ia supernova progenitors inferred from Ultraviolet Spectra
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: R J Foley, Robert P KirshnerAbstract:Two "twin" Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and Spectra, yet have different Ultraviolet (UV) continua as measured in Hubble Space Telescope Spectra and measurably different peak luminosities. We attribute the difference in the UV continua to significantly different progenitor metallicities. This is the first robust detection of different metallicities for SN Ia progenitors. Theoretical reasoning suggests that differences in metallicity also lead to differences in luminosity. SNe Ia with higher progenitor metallicities have lower 56Ni yields, and lower luminosities, for the same light-curve shape. SNe 2011by and 2011fe have different peak luminosities (Delta M_V = 0.6 mag), which correspond to different 56Ni yields: M_11fe(56Ni)/M_11by(56Ni) = 1.7^+0.7_-0.5. From theoretical models that account for different neutron to proton ratios in progenitors, the differences in 56Ni yields for SNe 2011by and 2011fe imply that their progenitor stars were above and below solar metallicity, respectively. Although we can distinguish progenitor metallicities in a qualitative way from UV data, the quantitative interpretation in terms of abundances is limited by the present state of theoretical models.
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luminosity indicators in the Ultraviolet Spectra of type ia supernovae
arXiv: Astrophysics, 2008Co-Authors: R J Foley, Alexei V Filippenko, Saurabh W JhaAbstract:We present a complete sample of International Ultraviolet Explorer and Hubble Space Telescope Ultraviolet (UV) Spectra of Type Ia supernovae (SNe Ia) through 2004. We measure the equivalent width (EW) and blueshifted velocity of the minimum of the one strong UV feature, Fe II 3250. We also quantify the slope of the near-UV Spectra using a new parameter, the ``UV ratio.'' We find that the velocity of the Fe II line does not correlate with light-curve shape, while the EW shows distinct behavior for the slow and fast-declining objects. Using precise Cepheid and surface brightness fluctuation distance measurements of 6 objects with UV Spectra observed near maximum light (a total of 12 Spectra), we determine that the UV ratio at maximum light is highly correlated with SN Ia luminosity. A larger sample of UV Spectra is necessary to increase the statistical certainty of these luminosity indicators and whether they can be combined with light-curve shape to improve measured SN Ia distances.
Richard F Mushotzky - One of the best experts on this subject based on the ideXlab platform.
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intrinsic absorption lines in seyfert 1 galaxies i Ultraviolet Spectra from the hubble space telescope
The Astrophysical Journal, 1999Co-Authors: Michael D Crenshaw, S B Kraemer, A Boggess, S P Maran, Richard F MushotzkyAbstract:We present a study of the intrinsic absorption lines in the Ultraviolet Spectra of Seyfert 1 galaxies. The study is based on Spectra from the Hubble Space Telescope and includes the Seyfert 1 galaxies observed with the Faint Object Spectrograph and Goddard High-Resolution Spectrograph at Spectral resolutions of λ/Δλ ≈1000-20,000 with good signal-to-noise ratios. We find that the fraction of Seyfert 1 galaxies that show intrinsic absorption associated with their active nuclei is more than one-half (10 of 17), which is much higher than previous estimates (3%-10%) based on IUE data. There is a one-to-one correspondence between Seyfert galaxies that show intrinsic UV absorption and X-ray "warm absorbers," indicating that these two phenomena are related. Although our sample is not complete, we conclude that intrinsic absorption represents an important component that needs to be integrated into our overall physical picture of active galaxies. The intrinsic UV absorption is generally characterized by high ionization: C IV and N V are seen in all 10 Seyfert galaxies with detected absorption (in addition to Lyα), whereas Si IV is present in only four of these Seyfert galaxies, and Mg II absorption is detected only in NGC 4151. The absorption lines are blueshifted (or in a few cases at rest) with respect to the narrow emission lines, indicating that the absorbing gas is undergoing net radial outflow. At high resolution, the absorption often splits into distinct kinematic components that show a wide range in widths (20-400 km s-1 FWHM), indicating macroscopic motions (e.g., radial velocity subcomponents or turbulence) within a component. The strong absorption components have cores that are much deeper than the continuum flux levels, indicating that the regions responsible for these components lie completely outside of the broad emission-line regions. Additional information on the covering factors and column densities can be derived from the absorption profiles in the high-resolution Spectra. The covering factor of the absorbing gas in the line of sight, relative to the total underlying emission, is Clos ≥ 0.86, on average. The global covering factor, which is the fraction of emission intercepted by the absorber averaged over all lines of sight, is Cglobal ≥ 0.5. Thus, structures covering large solid angles as seen by the central continuum source (e.g., spherical shells, sheets, or cones with large opening angles) are required. The individual absorptioncomponents show a wide range in C IV column densities (0.1-14 × 1014 cm-2), and the ratio of N V to C IV column density varies significantly from one absorption component to the next, even in the same Seyfert galaxy. Thus, the intrinsic absorption in a Seyfert 1 galaxy is typically comprised of distinct kinematic components that are characterized by a range in physical conditions (e.g., ionization parameter and hydrogen column density). Finally, we show evidence for extreme variability in the intrinsic absorption lines of NGC 3783. In addition to our earlier report of the appearance of a C IV absorption doublet at -560 km s-1 (relative to the emission lines) over 11 months, we have detected the appearance of another C IV doublet at -1420 km s-1 over 15 months. On the other hand, the C IV absorption lines of NGC 3516 and NGC 4151 were very stable over periods of 6 months and 4 years, respectively. Monitoring observations of individual Seyfert galaxies at higher time resolution are needed to distinguish between different sources of variability (variable ionization, motion of gas across the line of sight) and to determine the densities and radial locations of the absorption components.
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intrinsic absorption lines in seyfert 1 galaxies i Ultraviolet Spectra from the hubble space telescope
arXiv: Astrophysics, 1998Co-Authors: Michael D Crenshaw, S B Kraemer, A Boggess, S P Maran, Richard F MushotzkyAbstract:We present a study of the intrinsic absorption lines in the Ultraviolet Spectra of Seyfert 1 galaxies. We find that the fraction of Seyfert 1 galaxies that show absorption associated with their active nuclei is more than one-half (10/17), which is much higher than previous estimates (3 - 10%) . There is a one-to-one correspondence between Seyferts that show intrinsic UV absorption and X-ray ``warm absorbers''. The intrinsic UV absorption is generally characterized by high ionization: C IV and N V are seen in all 10 Seyferts with detected absorption (in addition to Ly-alpha), whereas Si IV is present in only four of these Seyferts, and Mg II absorption is only detected in NGC 4151. The absorption lines are blueshifted (or in a few cases at rest) with respect to the narrow emission lines, indicating that the absorbing gas is undergoing net radial outflow. At high resolution, the absorption often splits into distinct kinematic components that show a wide range in widths (20 - 400 km/s FWHM), indicating macroscopic motions (e.g., radial velocity subcomponents or turbulence) within a component. The strong absorption components have cores that are much deeper than the continuum flux levels, indicating that the regions responsible for these components lie completely outside of the broad emission-line regions. The covering factor of the absorbing gas in the line of sight, relative to the total underlying emission, is C > 0.86, on average. The global covering factor, which is the fraction of emission intercepted by the absorber averaged over all lines of sight, is C > 0.5.
