Structure and Formation of Elliptical and Spheroidal Galaxies

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dc.contributor.utaustinauthorKormendy, Johnen_US
dc.contributor.utaustinauthorFisher, David B.en_US
dc.contributor.utaustinauthorCornell, Mark E.en_US
dc.contributor.utaustinauthorBender, Ralfen_US
dc.creatorKormendy, Johnen_US
dc.creatorFisher, David B.en_US
dc.creatorCornell, Mark E.en_US
dc.creatorBender, Ralfen_US
dc.date.accessioned2016-10-28T19:36:37Z
dc.date.available2016-10-28T19:36:37Z
dc.date.issued2009-05en_US
dc.description.abstractNew surface photometry of all known elliptical galaxies in the Virgo cluster is combined with published data to derive composite profiles of brightness, ellipticity, position angle, isophote shape, and color over large radius ranges. These provide enough leverage to show that Sersic log I alpha r(1/n) functions fit the brightness profiles I(r) of nearly all ellipticals remarkably well over large dynamic ranges. Therefore, we can confidently identify departures from these profiles that are diagnostic of galaxy Formation. Two kinds of departures are seen at small radii. All 10 of our ellipticals with total absolute magnitudes M(VT) <= -21.66 have cuspy cores-"missing light"-at small radii. Cores are well known and naturally scoured by binary black holes (BHs) formed in dissipationless ("dry") mergers. All 17 ellipticals with -21.54 <= M(VT) <= -15.53 do not have cores. We find a new distinct component in these galaxies: all coreless ellipticals in our sample have extra light at the center above the inward extrapolation of the outer Sersic profile. In large ellipticals, the excess light is spatially resolved and resembles the central components predicted in numerical simulations of mergers of galaxies that contain gas. In the simulations, the gas dissipates, falls toward the center, undergoes a starburst, and builds a compact stellar component that, as in our observations, is distinct from the Sersic-function main body of the elliptical. But ellipticals with extra light also contain supermassive BHs. We suggest that the starburst has swamped core scouring by binary BHs. That is, we interpret extra light components as a signature of Formation in dissipative ("wet") mergers. Besides extra light, we find three new aspects to the ("E-E") dichotomy into two types of elliptical galaxies. Core galaxies are known to be slowly rotating, to have relatively anisotropic velocity distributions, and to have boxy isophotes. We show that they have Sersic indices n > 4 uncorrelated with M(VT). They also are alpha-element enhanced, implying short star-Formation timescales. And their stellar populations have a variety of ages but mostly are very old. Extra light ellipticals generally rotate rapidly, are more isotropic than core Es, and have disky isophotes. We show that they have n similar or equal to 3 +/- 1 almost uncorrelated with MVT and younger and less alpha-enhanced stellar populations. These are new clues to galaxy Formation. We suggest that extra light ellipticals got their low Sersic indices by forming in relatively few binary mergers, whereas giant ellipticals have n > 4 because they formed in larger numbers of mergers of more galaxies at once plus later heating during hierarchical clustering. We confirm that core Es contain X-ray-emitting gas whereas extra light Es generally do not. This leads us to suggest why the E-E dichotomy arose. If energy feedback from active galactic nuclei (AGNs) requires a "working surface" of hot gas, then this is present in core galaxies but absent in extra light galaxies. We suggest that AGN energy feedback is a strong function of galaxy mass: it is weak enough in small Es not to prevent merger starbursts but strong enough in giant Es and their progenitors to make dry mergers dry and to protect old stellar populations from late star Formation. Finally, we verify that there is a strong dichotomy between elliptical and spheroidal galaxies. Their properties are consistent with our understanding of their different Formation processes: mergers for ellipticals and conversion of late-type galaxies into spheroidals by environmental effects and by energy feedback from supernovae. In an appendix, we develop machinery to get realistic error estimates for Sersic parameters even when they are strongly coupled. And we discuss photometric dynamic ranges necessary to get robust results from Sersic fits.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipen_US
dc.identifierdoi:10.15781/T28G8FM0V
dc.identifier.citationKormendy, John, David B. Fisher, Mark E. Cornell, and Ralf Bender. "Structure and formation of elliptical and spheroidal galaxies." arXiv preprint arXiv:0810.1681 (May, 2008).en_US
dc.identifier.doi10.1088/0067-0049/182/1/216en_US
dc.identifier.issn0067-0049en_US
dc.identifier.urihttp://hdl.handle.net/2152/43027
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journal Supplement Seriesen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectgalaxies: elliptical and lenticular, cden_US
dc.subjectgalaxies: evolutionen_US
dc.subjectgalaxies:en_US
dc.subjectFormationen_US
dc.subjectgalaxies: nucleien_US
dc.subjectgalaxies: photometryen_US
dc.subjectgalaxies: structureen_US
dc.subjecthubble-space-telescopeen_US
dc.subjectdigital sky surveyen_US
dc.subjectultraluminous infrareden_US
dc.subjectgalaxiesen_US
dc.subjectsupermassive black-holesen_US
dc.subjectactive galactic nucleien_US
dc.subjectccd surfaceen_US
dc.subjectphotometryen_US
dc.subjectacs-virgo-clusteren_US
dc.subjectplanetary camera observationsen_US
dc.subjectsighten_US
dc.subjectvelocity distributionsen_US
dc.subjectfrance-hawaii telescopeen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleStructure and Formation of Elliptical and Spheroidal Galaxiesen_US
dc.typeReviewen_US

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