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Richard M Mcdermid - One of the best experts on this subject based on the ideXlab platform.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [alpha/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which similar to 40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (>= 10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above similar to 3.5 x 10(10) M-circle dot) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of =10 Gyr) stellar populations.
Tim P De Zeeuw - One of the best experts on this subject based on the ideXlab platform.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [alpha/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which similar to 40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (>= 10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above similar to 3.5 x 10(10) M-circle dot) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of =10 Gyr) stellar populations.
Michele Cappellari - One of the best experts on this subject based on the ideXlab platform.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [alpha/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which similar to 40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (>= 10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above similar to 3.5 x 10(10) M-circle dot) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of =10 Gyr) stellar populations.
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adaptive spatial binning of integral field spectroscopic data using voronoi tessellations
Monthly Notices of the Royal Astronomical Society, 2003Co-Authors: Michele Cappellari, Y CopinAbstract:We present new techniques to perform adaptive spatial binning of integral-field spectroscopic (IFS) data to reach a chosen Constant Signal-to-noise ratio per bin. These methods are required for the proper analysis of IFS observations, but can also be used for standard photometric imagery or any other two-dimensional data. Various schemes are tested and compared by binning and extracting the stellar kinematics of the Sa galaxy NGC 2273 from spectra obtained with the panoramic IFS SAURON.
Shravan M Hanasoge - One of the best experts on this subject based on the ideXlab platform.
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subsurface supergranular vertical flows as measured using large distance separations in time distance helioseismology
Solar Physics, 2013Co-Authors: T L Duvall, Shravan M HanasogeAbstract:As large-distance rays (say, 10 – 24°) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large-separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time–distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant travel-time Signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center–annulus travel-time difference [δt oi] in the separation range Δ=10 – 24∘ is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a Constant Signal from the vertical flow. Our measurement of this quantity, 5.1±0.1 seconds, is Constant over the distance range. This magnitude of the Signal cannot be caused by the level of upflow at cell centers seen at the photosphere of 10 m s−1 extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of 240 m s−1 at a depth of 2.3 Mm and a peak horizontal flow of 700 m s−1 at a depth of 1.6 Mm.
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subsurface supergranular vertical flows as measured using large distance separations in time distance helioseismology
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: T L Duvall, Shravan M HanasogeAbstract:As large--distance rays (say, 10\,-\,$24 ^\circ$) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time-distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant travel time Signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center--annulus travel time difference $[\delta t_{\rm{oi}}]$ in the separation range $\Delta=10$\,-\,$24 ^\circ$ is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a Constant Signal from the vertical flow. Our measurement of this quantity, $5.1 \pm 0.1\secs$, is Constant over the distance range. This magnitude of Signal cannot be caused by the level of upflow at cell centers seen at the photosphere of $10\ms$ extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of $240\ms$ at a depth of $2.3\Mm$ and a peak horizontal flow of $700\ms$ at a depth of $1.6\Mm$.
Harald Kuntschner - One of the best experts on this subject based on the ideXlab platform.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [alpha/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which similar to 40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (>= 10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above similar to 3.5 x 10(10) M-circle dot) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.
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the sauron project xvii stellar population analysis of the absorption line strength maps of 48 early type galaxies
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Harald Kuntschner, Michele Cappellari, Eric Emsellem, Roland Bacon, Roger L Davies, Tim P De Zeeuw, Jesus Falconbarroso, Davor Krajnovic, Richard M McdermidAbstract:(Abridged) We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hbeta, Fe5015, and Mgb, measured in the Lick/IDS system and spatially binned to a Constant Signal-to-noise, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. We find a large range of SSP-equivalent ages in our sample, of which ~40% of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of =10 Gyr) stellar populations.