Elliptical galaxies comprise primarily old stars, which collectively generate
a long-lasting feedback via stellar mass-loss and Type Ia SNe. This feedback
can be traced by X-ray-emitting hot gas in and around such galaxies, in which
little cool gas is typically present. However, the X-ray-inferred mass, energy,
and metal abundance of the hot gas are often found to be far less than what are
expected from the feedback, particularly in so-called low L_X/L_B ellipticals.
This "missing" stellar feedback is presumably lost in galaxy-wide outflows,
which can play an essential role in galaxy evolution (e.g., explaining the
observed color bi-modality of galaxies). We are developing a model that can be
used to properly interpret the X-ray data and to extract key information about
the dynamics of the feedback and its interplay with galactic environment.Comment: To be published in Highlights of Astronomy, Vol 15, XXVIIth IAU
  General Assembly, JD

Wang, Q. Daniel

English

arXiv

This is the pre-published version harvested from ArXiv. The published version is located at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7915475Elliptical galaxies comprise primarily old stars, which collectively generate a long-lasting feedback via stellar mass-loss and Type Ia SNe. This feedback can be traced by X-ray-emitting hot gas in and around such galaxies, in which little cool gas is typically present. However, the X-ray-inferred mass, energy, and metal abundance of the hot gas are often found to be far less than what are expected from the feedback, particularly in so-called low LX/LB ellipticals. This “missing” stellar feedback is presumably lost in galaxy-wide outflows, which can play an essential role in galaxy evolution (e.g., explaining the observed color bi-modality of galaxies). We are developing a model that can be used to properly interpret the X-ray data and to extract key information about the dynamics of the feedback and its interplay with galactic environment.284-28

Wang, QD

ScholarWorks@UMass Amherst

Confronting Feedback Simulations WithObservations Of Hot Gas In Elliptical GalaxiesItem Type ArticleAuthors Wang, QDDOI 10.1017/S1743921310009270Download date 2025-12-01 08:03:28Link to Item https://hdl.handle.net/20.500.14394/2654arXiv:1003.1763v1  [astro-ph.GA]  9 Mar 2010Title of your IAU SymposiumXXVIth IAU General Assembly, August 2006Dong-Woo Kim. Editorc© 2009 International Astronomical UnionDOI: 00.0000/X000000000000000XConfronting feedback simulations withobservations of hot gas in elliptical galaxiesQ. Daniel Wang11Department of Astronomy, University of Massachusetts,Amherst, MA 01003, USA email: wqd@astro.umass.eduKeywords. X-ray, elliptical galaxies, hot gas, galaxy evolutionElliptical galaxies comprise primarily old stars, which collectively generate a long-lastingfeedback via stellar mass-loss and Type Ia SNe. This feedback can be traced by X-ray-emittinghot gas in and around such galaxies, in which little cool gas is typically present. However, theX-ray-inferred mass, energy, and metal abundance of the hot gas are often found to be farless than what are expected from the feedback, particularly in so-called low LX/LB ellipticals.This “missing” stellar feedback is presumably lost in galaxy-wide outflows, which can play anessential role in galaxy evolution (e.g., explaining the observed color bi-modality of galaxies).We are developing a model that can be used to properly interpret the X-ray data and to extractkey information about the dynamics of the feedback and its interplay with galactic environment.First, we have constructed a 1-D model of the stellar feedback in the context of galaxyformation and evolution. The feedback is assumed to consist of two primary phases: 1) an initialburst during the bulge formation and 2) a subsequent long-lasting mass and energy injectionfrom stellar winds and Type Ia SNe of low-mass stars. An outward blastwave is initiated bythe burst and is maintained and enhanced by the long-lasting stellar feedback. This blastwavecan heat the surrounding medium not only in the galactic halo, but also in regions beyondthe virial radius. As a result, the smooth accretion of hot gas can be completely stopped. Thelong-lasting feedback can form a galactic bulge wind, which is reverse-shocked at a large radius,and can later evolve into a subsonic quasi-stable outflow as the energy injection decreases withtime. The two phases of the feedback thus re-enforce each-other’s impact on the gas dynamics.Present-day elliptical galaxies with significant amounts of hot gas are most likely in subsonicoutflow states. The exact properties of such an outflow depend on the galaxy formation historyand environment. This dependence and variance may explain the large dispersion in the LX/LBratios of elliptical galaxies.Second, to quantitatively compare the simulations with X-ray observations, we have conductedvarious 3-D hydrodynamical simulations with the adaptive mesh refinement code FLASH toinvestigate the physical properties of hot gas in and around elliptical galaxies. We have developedan embedding scheme of individual supernova remnant seeds, which allows us to examine, forthe first time, the effect of sporadic SNe on the density, temperature, and iron ejecta distributionof the hot gas as well as the resultant X-ray morphology and spectrum. We find that the SNeproduce a wind/outflow with highly filamentary density structures and patchy ejecta. Comparedwith a 1-D spherical wind model, the non-uniformity of simulated gas density, temperature, andmetallicity substantially alters the spectral shape and increases the diffuse X-ray luminosity.The differential emission measure as a function of temperature of the simulated gas exhibits alog-normal distribution, with a peak value much lower than that of the corresponding 1D model.The bulk of the X-ray emission comes from the relatively low temperature and low abundancegas shells associated with SN blastwaves. SN ejecta are not well mixed with the ambient mediumand typically remain very hot in the central region. Driven by the buoyancy, the iron-rich gason average moves substantially faster than the medium and only gradually mixes with it onthe way out. As a result, apparent increasing temperature and metal abundance with off-centerdistance can arise in the region, mimicking what have been observed in elliptical galaxies. Theseresults, at least partly, account for the apparent lack of evidence for iron enrichment in the soft0JD8: Hot Interstellar Matter in Elliptical Galaxies 1X-ray-emitting gas in galactic bulges and intermediate-mass elliptical galaxies. More details willbe presented in Tang & Wang (2010).ReferencesTang, S. K., & Wang, Q. D. 2010, MNRAS, submitted.

Confronting Feedback Simulations With Observations Of Hot Gas In Elliptical Galaxies

Elliptical galaxies comprise primarily old stars, which collectively generate a long-lasting feedback via stellar mass-loss and Type Ia SNe. This feedback can be traced by X-ray-emitting hot gas in and around such galaxies, in which little cool gas is typically present. However, the X-ray-inferred mass, energy, and metal abundance of the hot gas are often found to be far less than what are expected from the feedback, particularly in so-called low LX/LB ellipticals. This “missing” stellar feedback is presumably lost in galaxy-wide outflows, which can play an essential role in galaxy evolution (e.g., explaining the observed color bi-modality of galaxies). We are developing a model that can be used to properly interpret the X-ray data and to extract key information about the dynamics of the feedback and its interplay with galactic environment

University of Massachusetts AmherstScholarWorks@UMass AmherstAstronomy Department Faculty Publication Series Astronomy2009Confronting feedback simulations withobservations of hot gas in elliptical galaxiesQD WangUniversity of Massachusetts - AmherstFollow this and additional works at: https://scholarworks.umass.edu/astro_faculty_pubsPart of the Astrophysics and Astronomy CommonsThis Article is brought to you for free and open access by the Astronomy at ScholarWorks@UMass Amherst. It has been accepted for inclusion inAstronomy Department Faculty Publication Series by an authorized administrator of ScholarWorks@UMass Amherst. For more information, pleasecontact scholarworks@library.umass.edu.Recommended CitationWang, QD, "Confronting feedback simulations with observations of hot gas in elliptical galaxies" (2009). Proceedings of theInternational Astronomical Union. 1038.10.1017/S1743921310009270arXiv:1003.1763v1  [astro-ph.GA]  9 Mar 2010Title of your IAU SymposiumXXVIth IAU General Assembly, August 2006Dong-Woo Kim. Editorc© 2009 International Astronomical UnionDOI: 00.0000/X000000000000000XConfronting feedback simulations withobservations of hot gas in elliptical galaxiesQ. Daniel Wang11Department of Astronomy, University of Massachusetts,Amherst, MA 01003, USA email: wqd@astro.umass.eduKeywords. X-ray, elliptical galaxies, hot gas, galaxy evolutionElliptical galaxies comprise primarily old stars, which collectively generate a long-lastingfeedback via stellar mass-loss and Type Ia SNe. This feedback can be traced by X-ray-emittinghot gas in and around such galaxies, in which little cool gas is typically present. However, theX-ray-inferred mass, energy, and metal abundance of the hot gas are often found to be farless than what are expected from the feedback, particularly in so-called low LX/LB ellipticals.This “missing” stellar feedback is presumably lost in galaxy-wide outflows, which can play anessential role in galaxy evolution (e.g., explaining the observed color bi-modality of galaxies).We are developing a model that can be used to properly interpret the X-ray data and to extractkey information about the dynamics of the feedback and its interplay with galactic environment.First, we have constructed a 1-D model of the stellar feedback in the context of galaxyformation and evolution. The feedback is assumed to consist of two primary phases: 1) an initialburst during the bulge formation and 2) a subsequent long-lasting mass and energy injectionfrom stellar winds and Type Ia SNe of low-mass stars. An outward blastwave is initiated bythe burst and is maintained and enhanced by the long-lasting stellar feedback. This blastwavecan heat the surrounding medium not only in the galactic halo, but also in regions beyondthe virial radius. As a result, the smooth accretion of hot gas can be completely stopped. Thelong-lasting feedback can form a galactic bulge wind, which is reverse-shocked at a large radius,and can later evolve into a subsonic quasi-stable outflow as the energy injection decreases withtime. The two phases of the feedback thus re-enforce each-other’s impact on the gas dynamics.Present-day elliptical galaxies with significant amounts of hot gas are most likely in subsonicoutflow states. The exact properties of such an outflow depend on the galaxy formation historyand environment. This dependence and variance may explain the large dispersion in the LX/LBratios of elliptical galaxies.Second, to quantitatively compare the simulations with X-ray observations, we have conductedvarious 3-D hydrodynamical simulations with the adaptive mesh refinement code FLASH toinvestigate the physical properties of hot gas in and around elliptical galaxies. We have developedan embedding scheme of individual supernova remnant seeds, which allows us to examine, forthe first time, the effect of sporadic SNe on the density, temperature, and iron ejecta distributionof the hot gas as well as the resultant X-ray morphology and spectrum. We find that the SNeproduce a wind/outflow with highly filamentary density structures and patchy ejecta. Comparedwith a 1-D spherical wind model, the non-uniformity of simulated gas density, temperature, andmetallicity substantially alters the spectral shape and increases the diffuse X-ray luminosity.The differential emission measure as a function of temperature of the simulated gas exhibits alog-normal distribution, with a peak value much lower than that of the corresponding 1D model.The bulk of the X-ray emission comes from the relatively low temperature and low abundancegas shells associated with SN blastwaves. SN ejecta are not well mixed with the ambient mediumand typically remain very hot in the central region. Driven by the buoyancy, the iron-rich gason average moves substantially faster than the medium and only gradually mixes with it onthe way out. As a result, apparent increasing temperature and metal abundance with off-centerdistance can arise in the region, mimicking what have been observed in elliptical galaxies. Theseresults, at least partly, account for the apparent lack of evidence for iron enrichment in the soft0JD8: Hot Interstellar Matter in Elliptical Galaxies 1X-ray-emitting gas in galactic bulges and intermediate-mass elliptical galaxies. More details willbe presented in Tang & Wang (2010).ReferencesTang, S. K., & Wang, Q. D. 2010, MNRAS, submitted.

Confronting feedback simulations with observations of hot gas in elliptical galaxies

Elliptical galaxies comprise primarily old stars, which collectively generate a long-lasting feedback via stellar mass-loss and Type Ia SNe. This feedback can be traced by X-ray-emitting hot gas in and around such galaxies, in which little cool gas is typically present. However, the X-ray-inferred mass, energy, and metal abundance of the hot gas are often found to be far less than what are expected from the feedback, particularly in so-called low LX/LB ellipticals. This “missing” stellar feedback is presumably lost in galaxy-wide outflows, which can play an essential role in galaxy evolution (e.g., explaining the observed color bi-modality of galaxies). We are developing a model that can be used to properly interpret the X-ray data and to extract key information about the dynamics of the feedback and its interplay with galactic environment.</jats:p

Q. Daniel Wang

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Proceedings of the International Astronomical Union

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Confronting feedback simulations with observations of hot gas in elliptical galaxies

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