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Matthew Hayes - One of the best experts on this subject based on the ideXlab platform.
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the lyman alpha Reference Sample xi efficient turbulence driven ly alpha escape and the analysis of ir co and c ii 158 mu m
arXiv: Astrophysics of Galaxies, 2020Co-Authors: J Puschnig, Goran Ostlin, Matthew Hayes, John M Cannon, Joanna S Bridge, Daniel Kunth, I Smirnovapinchukova, B Husemann, Edmund Christian Herenz, Matteo MessaAbstract:We study the global dust and (molecular) gas content in the Lyman Alpha Reference Sample (LARS), i.e. 14 local star-forming galaxies. We characterize their interstellar medium and relate newly derived properties to quantities relevant for Ly$\alpha$ escape. We observed LARS galaxies with Herschel/PACS, SOFIA/FIFI-LS, the IRAM 30m telescope and APEX, targeting far-infrared (FIR) continuum and emission lines of [C II]158$\mu$m, [O I]63$\mu$m, [O III]88$\mu$m and low-J CO lines. Using Bayesian methods we derive dust model parameters and estimate total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [C II]158$\mu$m and [O I]63$\mu$m luminosities. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from $\sim$0.5-100 $M_{\odot}\ yr^{-1}$, gas fractions between $\sim$15-80% and gas depletion times ranging from a few hundred Myr up to more than 10 Gyr. The distribution of LARS galaxies in the $\Sigma_{gas}$ vs. $\Sigma_{SFR}$ (Kennicutt-Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, i.e. relatively high gas surface densities ($\Sigma_{gas}$) and low star formation rate densities ($\Sigma_{SFR}$), have by far the highest Ly$\alpha$ escape fraction. A strong $\sim$linear relation is found between Ly$\alpha$ escape fraction and the total gas (HI+H$_2$) depletion time. We argue that the Ly$\alpha$ escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Ly$\alpha$ photons out of resonance close to the places where they originate. We further report on an extreme [C II]158$\mu$m excess in LARS 5, corresponding to $\sim$14$\pm$3% of the FIR luminosity, i.e. the most extreme [C II]-to-FIR ratio observed in a non-AGN galaxy to date.
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the lyman alpha Reference Sample x predicting lyα output from star forming galaxies using multivariate regression
The Astrophysical Journal, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Ly alpha radiation from star-forming galaxies is a long-standing problem in astrophysics. The ability to predict the Ly alpha luminosity of galaxies would ...
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lyman alpha Reference Sample x predicting lyman alpha output from starforming galaxies using multivariate regression
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Lyman $\alpha$ (Ly$\alpha$) radiation from star-forming galaxies is a long standing problem in astrophysics. The ability to predict the Ly$\alpha$ luminosity of galaxies would open up new ways of exploring the Epoch of Reionization (EoR), and to estimate Ly$\alpha$ emission from galaxies in cosmological simulations where radiative transfer calculations cannot be done. We apply multivariate regression methods to the Lyman Alpha Reference Sample dataset to obtain a relation between the galaxy properties and the emitted Ly$\alpha$. The derived relation predicts the Ly$\alpha$ luminosity of our galaxy Sample to good accuracy, regardless of whether we consider only direct observables (root-mean-square (RMS) dispersion around the relation of $\sim 0.19$ dex) or derived physical quantities (RMS $\sim 0.27$ dex). We confirm the predictive ability on a separate Sample of compact star-forming galaxies and find that the prediction works well, but that aperture effects on measured Ly$\alpha$ luminosity may be important, depending on the redshift of the galaxy. We apply statistical feature selection techniques to determine an order of importance of the variables in our dataset, enabling future observations to be optimized for predictive ability. When using physical variables, we are able to determine that the most important predictive parameters are, in order, star formation rate, dust extinction, compactness and the gas covering fraction. We discuss the application of our results in terms of studying the EoR and intensity mapping experiments.
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the lyman alpha Reference Sample ix revelations from deep surface photometry
Astronomy and Astrophysics, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample h ...
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the lyman alpha Reference Sample ix revelations from deep surface photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:The Lyman Alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample has been well-studied in terms of LyA and other emission line properties, such as HI mass, gas kinematics, and morphology. We analyze deep surface photometry of the LARS Sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a Sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are [...] analyzed, as well as isophotal asymmetry profiles for each galaxy. [...] We compare the LARS to the properties of the BCG Sample and highlight the differences. Several diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest isophotes [...]. The ground-based photometry [...] reveals previously unexplored isophotes [...]. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. [...] The galaxies in the LARS Sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two Samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha. [abridged]
Goran Ostlin - One of the best experts on this subject based on the ideXlab platform.
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the lyman alpha Reference Sample xi efficient turbulence driven ly alpha escape and the analysis of ir co and c ii 158 mu m
arXiv: Astrophysics of Galaxies, 2020Co-Authors: J Puschnig, Goran Ostlin, Matthew Hayes, John M Cannon, Joanna S Bridge, Daniel Kunth, I Smirnovapinchukova, B Husemann, Edmund Christian Herenz, Matteo MessaAbstract:We study the global dust and (molecular) gas content in the Lyman Alpha Reference Sample (LARS), i.e. 14 local star-forming galaxies. We characterize their interstellar medium and relate newly derived properties to quantities relevant for Ly$\alpha$ escape. We observed LARS galaxies with Herschel/PACS, SOFIA/FIFI-LS, the IRAM 30m telescope and APEX, targeting far-infrared (FIR) continuum and emission lines of [C II]158$\mu$m, [O I]63$\mu$m, [O III]88$\mu$m and low-J CO lines. Using Bayesian methods we derive dust model parameters and estimate total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [C II]158$\mu$m and [O I]63$\mu$m luminosities. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from $\sim$0.5-100 $M_{\odot}\ yr^{-1}$, gas fractions between $\sim$15-80% and gas depletion times ranging from a few hundred Myr up to more than 10 Gyr. The distribution of LARS galaxies in the $\Sigma_{gas}$ vs. $\Sigma_{SFR}$ (Kennicutt-Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, i.e. relatively high gas surface densities ($\Sigma_{gas}$) and low star formation rate densities ($\Sigma_{SFR}$), have by far the highest Ly$\alpha$ escape fraction. A strong $\sim$linear relation is found between Ly$\alpha$ escape fraction and the total gas (HI+H$_2$) depletion time. We argue that the Ly$\alpha$ escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Ly$\alpha$ photons out of resonance close to the places where they originate. We further report on an extreme [C II]158$\mu$m excess in LARS 5, corresponding to $\sim$14$\pm$3% of the FIR luminosity, i.e. the most extreme [C II]-to-FIR ratio observed in a non-AGN galaxy to date.
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the lyman alpha Reference Sample x predicting lyα output from star forming galaxies using multivariate regression
The Astrophysical Journal, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Ly alpha radiation from star-forming galaxies is a long-standing problem in astrophysics. The ability to predict the Ly alpha luminosity of galaxies would ...
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lyman alpha Reference Sample x predicting lyman alpha output from starforming galaxies using multivariate regression
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Lyman $\alpha$ (Ly$\alpha$) radiation from star-forming galaxies is a long standing problem in astrophysics. The ability to predict the Ly$\alpha$ luminosity of galaxies would open up new ways of exploring the Epoch of Reionization (EoR), and to estimate Ly$\alpha$ emission from galaxies in cosmological simulations where radiative transfer calculations cannot be done. We apply multivariate regression methods to the Lyman Alpha Reference Sample dataset to obtain a relation between the galaxy properties and the emitted Ly$\alpha$. The derived relation predicts the Ly$\alpha$ luminosity of our galaxy Sample to good accuracy, regardless of whether we consider only direct observables (root-mean-square (RMS) dispersion around the relation of $\sim 0.19$ dex) or derived physical quantities (RMS $\sim 0.27$ dex). We confirm the predictive ability on a separate Sample of compact star-forming galaxies and find that the prediction works well, but that aperture effects on measured Ly$\alpha$ luminosity may be important, depending on the redshift of the galaxy. We apply statistical feature selection techniques to determine an order of importance of the variables in our dataset, enabling future observations to be optimized for predictive ability. When using physical variables, we are able to determine that the most important predictive parameters are, in order, star formation rate, dust extinction, compactness and the gas covering fraction. We discuss the application of our results in terms of studying the EoR and intensity mapping experiments.
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the lyman alpha Reference Sample ix revelations from deep surface photometry
Astronomy and Astrophysics, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample h ...
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the lyman alpha Reference Sample ix revelations from deep surface photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:The Lyman Alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample has been well-studied in terms of LyA and other emission line properties, such as HI mass, gas kinematics, and morphology. We analyze deep surface photometry of the LARS Sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a Sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are [...] analyzed, as well as isophotal asymmetry profiles for each galaxy. [...] We compare the LARS to the properties of the BCG Sample and highlight the differences. Several diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest isophotes [...]. The ground-based photometry [...] reveals previously unexplored isophotes [...]. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. [...] The galaxies in the LARS Sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two Samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha. [abridged]
John M Cannon - One of the best experts on this subject based on the ideXlab platform.
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the lyman alpha Reference Sample xi efficient turbulence driven ly alpha escape and the analysis of ir co and c ii 158 mu m
arXiv: Astrophysics of Galaxies, 2020Co-Authors: J Puschnig, Goran Ostlin, Matthew Hayes, John M Cannon, Joanna S Bridge, Daniel Kunth, I Smirnovapinchukova, B Husemann, Edmund Christian Herenz, Matteo MessaAbstract:We study the global dust and (molecular) gas content in the Lyman Alpha Reference Sample (LARS), i.e. 14 local star-forming galaxies. We characterize their interstellar medium and relate newly derived properties to quantities relevant for Ly$\alpha$ escape. We observed LARS galaxies with Herschel/PACS, SOFIA/FIFI-LS, the IRAM 30m telescope and APEX, targeting far-infrared (FIR) continuum and emission lines of [C II]158$\mu$m, [O I]63$\mu$m, [O III]88$\mu$m and low-J CO lines. Using Bayesian methods we derive dust model parameters and estimate total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [C II]158$\mu$m and [O I]63$\mu$m luminosities. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from $\sim$0.5-100 $M_{\odot}\ yr^{-1}$, gas fractions between $\sim$15-80% and gas depletion times ranging from a few hundred Myr up to more than 10 Gyr. The distribution of LARS galaxies in the $\Sigma_{gas}$ vs. $\Sigma_{SFR}$ (Kennicutt-Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, i.e. relatively high gas surface densities ($\Sigma_{gas}$) and low star formation rate densities ($\Sigma_{SFR}$), have by far the highest Ly$\alpha$ escape fraction. A strong $\sim$linear relation is found between Ly$\alpha$ escape fraction and the total gas (HI+H$_2$) depletion time. We argue that the Ly$\alpha$ escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Ly$\alpha$ photons out of resonance close to the places where they originate. We further report on an extreme [C II]158$\mu$m excess in LARS 5, corresponding to $\sim$14$\pm$3% of the FIR luminosity, i.e. the most extreme [C II]-to-FIR ratio observed in a non-AGN galaxy to date.
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the lyman alpha Reference Sample x predicting lyα output from star forming galaxies using multivariate regression
The Astrophysical Journal, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Ly alpha radiation from star-forming galaxies is a long-standing problem in astrophysics. The ability to predict the Ly alpha luminosity of galaxies would ...
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lyman alpha Reference Sample x predicting lyman alpha output from starforming galaxies using multivariate regression
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Lyman $\alpha$ (Ly$\alpha$) radiation from star-forming galaxies is a long standing problem in astrophysics. The ability to predict the Ly$\alpha$ luminosity of galaxies would open up new ways of exploring the Epoch of Reionization (EoR), and to estimate Ly$\alpha$ emission from galaxies in cosmological simulations where radiative transfer calculations cannot be done. We apply multivariate regression methods to the Lyman Alpha Reference Sample dataset to obtain a relation between the galaxy properties and the emitted Ly$\alpha$. The derived relation predicts the Ly$\alpha$ luminosity of our galaxy Sample to good accuracy, regardless of whether we consider only direct observables (root-mean-square (RMS) dispersion around the relation of $\sim 0.19$ dex) or derived physical quantities (RMS $\sim 0.27$ dex). We confirm the predictive ability on a separate Sample of compact star-forming galaxies and find that the prediction works well, but that aperture effects on measured Ly$\alpha$ luminosity may be important, depending on the redshift of the galaxy. We apply statistical feature selection techniques to determine an order of importance of the variables in our dataset, enabling future observations to be optimized for predictive ability. When using physical variables, we are able to determine that the most important predictive parameters are, in order, star formation rate, dust extinction, compactness and the gas covering fraction. We discuss the application of our results in terms of studying the EoR and intensity mapping experiments.
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the lyman alpha Reference Sample ix revelations from deep surface photometry
Astronomy and Astrophysics, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample h ...
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the lyman alpha Reference Sample ix revelations from deep surface photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:The Lyman Alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample has been well-studied in terms of LyA and other emission line properties, such as HI mass, gas kinematics, and morphology. We analyze deep surface photometry of the LARS Sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a Sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are [...] analyzed, as well as isophotal asymmetry profiles for each galaxy. [...] We compare the LARS to the properties of the BCG Sample and highlight the differences. Several diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest isophotes [...]. The ground-based photometry [...] reveals previously unexplored isophotes [...]. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. [...] The galaxies in the LARS Sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two Samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha. [abridged]
Andreas Sandberg - One of the best experts on this subject based on the ideXlab platform.
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the lyman alpha Reference Sample ix revelations from deep surface photometry
Astronomy and Astrophysics, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample h ...
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the lyman alpha Reference Sample ix revelations from deep surface photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:The Lyman Alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample has been well-studied in terms of LyA and other emission line properties, such as HI mass, gas kinematics, and morphology. We analyze deep surface photometry of the LARS Sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a Sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are [...] analyzed, as well as isophotal asymmetry profiles for each galaxy. [...] We compare the LARS to the properties of the BCG Sample and highlight the differences. Several diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest isophotes [...]. The ground-based photometry [...] reveals previously unexplored isophotes [...]. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. [...] The galaxies in the LARS Sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two Samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha. [abridged]
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the lyman alpha Reference Sample ii hubble space telescope imaging results integrated properties and trends
The Astrophysical Journal, 2014Co-Authors: Goran Ostlin, Matthew Hayes, Jens Melinder, Lucia Guaita, Andreas Sandberg, Florent Duval, Angela Adamo, D SchaererAbstract:We report new results regarding the Ly alpha output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Ly alpha, H alpha, and UV, and maps of H alpha/H beta, Ly alpha equivalent width (EW), and Ly alpha/H alpha. We present Ly alpha and UV radial light profiles and show they are well-fitted by Sersic profiles, but Ly alpha profiles show indices systematically lower than those of the UV (n approximate to 1-2 instead of greater than or similar to 4). This reveals a general lack of the central concentration in Ly alpha that is ubiquitous in the UV. Photometric growth curves increase more slowly for Ly alpha than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii approximate to 10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the Sample in large apertures, and show total Ly alpha luminosities to be independent of all other quantities. Normalized Ly alpha throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Ly alpha emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Ly alpha and UV Samples. A few galaxies have EWs above 50 angstrom, and one shows f(esc)(Ly alpha) of 80%; such objects have not previously been reported at low-z.
Daniel Kunth - One of the best experts on this subject based on the ideXlab platform.
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the lyman alpha Reference Sample xi efficient turbulence driven ly alpha escape and the analysis of ir co and c ii 158 mu m
arXiv: Astrophysics of Galaxies, 2020Co-Authors: J Puschnig, Goran Ostlin, Matthew Hayes, John M Cannon, Joanna S Bridge, Daniel Kunth, I Smirnovapinchukova, B Husemann, Edmund Christian Herenz, Matteo MessaAbstract:We study the global dust and (molecular) gas content in the Lyman Alpha Reference Sample (LARS), i.e. 14 local star-forming galaxies. We characterize their interstellar medium and relate newly derived properties to quantities relevant for Ly$\alpha$ escape. We observed LARS galaxies with Herschel/PACS, SOFIA/FIFI-LS, the IRAM 30m telescope and APEX, targeting far-infrared (FIR) continuum and emission lines of [C II]158$\mu$m, [O I]63$\mu$m, [O III]88$\mu$m and low-J CO lines. Using Bayesian methods we derive dust model parameters and estimate total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [C II]158$\mu$m and [O I]63$\mu$m luminosities. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from $\sim$0.5-100 $M_{\odot}\ yr^{-1}$, gas fractions between $\sim$15-80% and gas depletion times ranging from a few hundred Myr up to more than 10 Gyr. The distribution of LARS galaxies in the $\Sigma_{gas}$ vs. $\Sigma_{SFR}$ (Kennicutt-Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, i.e. relatively high gas surface densities ($\Sigma_{gas}$) and low star formation rate densities ($\Sigma_{SFR}$), have by far the highest Ly$\alpha$ escape fraction. A strong $\sim$linear relation is found between Ly$\alpha$ escape fraction and the total gas (HI+H$_2$) depletion time. We argue that the Ly$\alpha$ escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Ly$\alpha$ photons out of resonance close to the places where they originate. We further report on an extreme [C II]158$\mu$m excess in LARS 5, corresponding to $\sim$14$\pm$3% of the FIR luminosity, i.e. the most extreme [C II]-to-FIR ratio observed in a non-AGN galaxy to date.
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the lyman alpha Reference Sample x predicting lyα output from star forming galaxies using multivariate regression
The Astrophysical Journal, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Ly alpha radiation from star-forming galaxies is a long-standing problem in astrophysics. The ability to predict the Ly alpha luminosity of galaxies would ...
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lyman alpha Reference Sample x predicting lyman alpha output from starforming galaxies using multivariate regression
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Axel Runnholm, Goran Ostlin, Matthew Hayes, Jens Melinder, John M Cannon, Emil Riverathorsen, Daniel KunthAbstract:Understanding the production and escape of Lyman $\alpha$ (Ly$\alpha$) radiation from star-forming galaxies is a long standing problem in astrophysics. The ability to predict the Ly$\alpha$ luminosity of galaxies would open up new ways of exploring the Epoch of Reionization (EoR), and to estimate Ly$\alpha$ emission from galaxies in cosmological simulations where radiative transfer calculations cannot be done. We apply multivariate regression methods to the Lyman Alpha Reference Sample dataset to obtain a relation between the galaxy properties and the emitted Ly$\alpha$. The derived relation predicts the Ly$\alpha$ luminosity of our galaxy Sample to good accuracy, regardless of whether we consider only direct observables (root-mean-square (RMS) dispersion around the relation of $\sim 0.19$ dex) or derived physical quantities (RMS $\sim 0.27$ dex). We confirm the predictive ability on a separate Sample of compact star-forming galaxies and find that the prediction works well, but that aperture effects on measured Ly$\alpha$ luminosity may be important, depending on the redshift of the galaxy. We apply statistical feature selection techniques to determine an order of importance of the variables in our dataset, enabling future observations to be optimized for predictive ability. When using physical variables, we are able to determine that the most important predictive parameters are, in order, star formation rate, dust extinction, compactness and the gas covering fraction. We discuss the application of our results in terms of studying the EoR and intensity mapping experiments.
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the lyman alpha Reference Sample ix revelations from deep surface photometry
Astronomy and Astrophysics, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample h ...
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the lyman alpha Reference Sample ix revelations from deep surface photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Genoveva Micheva, Goran Ostlin, Erik Zackrisson, Matthew Hayes, Jens Melinder, Lucia Guaita, John M Cannon, Joanna S Bridge, Daniel Kunth, Andreas SandbergAbstract:The Lyman Alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The Sample has been well-studied in terms of LyA and other emission line properties, such as HI mass, gas kinematics, and morphology. We analyze deep surface photometry of the LARS Sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a Sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are [...] analyzed, as well as isophotal asymmetry profiles for each galaxy. [...] We compare the LARS to the properties of the BCG Sample and highlight the differences. Several diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest isophotes [...]. The ground-based photometry [...] reveals previously unexplored isophotes [...]. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. [...] The galaxies in the LARS Sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two Samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha. [abridged]
