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Kinematic Properties of Early-Type Galaxy Haloes Using Planetary Nebulae

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Kinematic Properties of Early-Type Galaxy Haloes Using Planetary Nebulae San Jose State University SJSU ScholarWorks Faculty Publications Physics and Astronomy 1-1-2009 Kinematic properties of early-type galaxy haloes using planetary nebulae L. Coccato Max-Plank-Institut für Extraterrestrische Physik O. Gerhard Max-Plank-Institut für Extraterrestrische Physik M. Arnaboldi European Southern Observatory P. Das Max-Plank-Institut für Extraterrestrische Physik N. G. Douglas Kapteyn Astronomical Institute See next page for additional authors Follow this and additional works at: https://scholarworks.sjsu.edu/physics_astron_pub Part of the Astrophysics and Astronomy Commons Recommended Citation L. Coccato, O. Gerhard, M. Arnaboldi, P. Das, N. G. Douglas, K. Kuijken, M. R. Merrifield, N. R. Napolitano, Aaron J. Romanowsky, E. Noordermeer, M. Capaccioli, A. Cortesi, F. De Lorenzi, and K. C. Freeman. "Kinematic properties of early-type galaxy haloes using planetary nebulae" Monthly Notices of the Royal Astronomical Society (2009): 1249-1283. https://doi.org/10.1111/j.1365-2966.2009.14417.x This Article is brought to you for free and open access by the Physics and Astronomy at SJSU ScholarWorks. It has been accepted for inclusion in Faculty Publications by an authorized administrator of SJSU ScholarWorks. For more information, please contact [email protected]. Authors L. Coccato, O. Gerhard, M. Arnaboldi, P. Das, N. G. Douglas, K. Kuijken, M. R. Merrifield, N. R. Napolitano, Aaron J. Romanowsky, E. Noordermeer, M. Capaccioli, A. Cortesi, F. De Lorenzi, and K. C. Freeman This article is available at SJSU ScholarWorks: https://scholarworks.sjsu.edu/physics_astron_pub/11 Mon. Not. R. Astron. Soc. 394, 1249–1283 (2009) doi:10.1111/j.1365-2966.2009.14417.x * Kinematic properties of early-type galaxy haloes using planetary nebulae L. Coccato,1† O. Gerhard,1 M. Arnaboldi,2,3 P. Das, 1 N. G. Douglas,4 K. Kuijken,5 M. R. Merrifield,6 N. R. Napolitano,7 E. Noordermeer,6 A. J. Romanowsky,8,9 M. Capaccioli,10,11 A. Cortesi,6 F. De Lorenzi1 and K. C. Freeman12 1Max-Plank-Institut fur¨ Extraterrestrische Physik, Giessenbachstraße, D-85741 Garching bei M unchen,¨ Germany 2European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei M unchen,¨ Germany 3INAF, Osservatorio Astronomico di Pino Torinese, I-10025 Pino Torinese, Italy 4Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, the Netherlands 5Leiden Observatory, Leiden University, PO Box 9513, 2300RA Leiden, the Netherlands 6School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD 7INAF-Observatory of Capodimonte, Salita Moiariello, 16, 80131, Naples, Italy 8UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA 9Departamento de F´ısica, Universidad de Concepci on,´ Casilla 160-C, Concepcion, ´ Chile 10Dipartimento di Scienze Fisiche, Universit a´ Federico II, Via Cinthia, 80126, Naples, Italy 11INAF-VSTceN, Salita Moiariello, 16, 80131, Naples, Italy 12Research School of Astronomy & Astrophysics, ANU, Canberra, Australia Accepted 2008 December 18. Received 2008 December 18; in original form 2008 September 15 ABSTRACT We present new planetary nebulae (PNe) positions, radial velocities and magnitudes for six early-type galaxies obtained with the Planetary Nebulae Spectrograph (PNS), along with derived two-dimensional velocity and velocity dispersion fields, and the α parameters (i.e. the number of PNe per unit luminosity). We also present new deep absorption-line long- slit kinematics for three galaxies in the sample, obtained with the FOcal Reducer and low dispersion Spectrograph (FORS2) at the Very Large Telescope (VLT). We extend this study to include additional 10 early-type galaxies with PNe radial velocity measurements available from the literature, including previous PNS studies, in order to obtain a broader description of the outer-halo kinematics in early-type galaxies. These data extend the information derived from stellar absorption-line kinematics to typically several and up to 8 effective radii. The combination of photometry, absorption-line and PNe kinematics shows (i) a good agreement between the PNe number density distribution and the stellar surface brightness in the region where the two data sets overlap; (ii) a good agreement between PNe and absorption- line kinematics; (iii) that the mean rms velocity profiles fall into two groups, with part of the galaxies characterized by slowly decreasing profiles and the remainder having steeply falling profiles; (iv) a larger variety of velocity dispersion radial profiles; (v) that twists and misalignments in the velocity fields are more frequent at large radii, including some fast rotator galaxies; (vi) that outer haloes are characterized by more complex radial profiles of the specific angular momentum-related λR parameter than observed within 1 Re; (vii) that many objects are more rotationally dominated at large radii than in their central parts and (viii) that the halo kinematics are correlated with other galaxy properties, such as total B band and X-ray *Based in part on observations made with the William Herschel Telescope operated by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos on the island of La Palma, of the Instituto de Astrof´ısica de Canarias, and on observations collected at the European Southern Observatory, Chile, Program: 76.B-0788(A). †E-mail: [email protected] ©C 2009 The Authors. Journal compilation ©C 2009 RAS 1250 L. Coccato et al. luminosity, isophotal shape, total stellar mass, V/σ and α parameter, with a clear separation between fast and slow rotators. Key words: galaxies: elliptical and lenticular, cD – galaxies: general – galaxies: haloes – galaxies: kinematics and dynamics. Some of the main aims of galaxy formation studies are to under­ 1 INTRODUCTION stand the mechanisms that allow galaxies to evolve from the blue The dynamics of galaxies provide fundamental information on their cloud to the red sequence, and to differentiate between processes origin and evolution. Our knowledge of the kinematics and dy­ that form early-type galaxies that are fast or slow rotators. Numer­ namics of early-type galaxies is mainly based on measurements ical simulations suggest that red-sequence galaxies are formed by of the first four moments of the line-of-sight velocity distribution mergers of galaxies in the blue cloud, followed by a quenching (LOSVD) from stellar absorption lines. These measurements are of the star formation (e.g. Cattaneo et al. 2006; Faber et al. 2007; generally confined to within 1–2 effective radii (Re) and can be Kang, van den Bosch & Pasquali 2007; Romeo et al. 2008). The obtained with long slits or integral-field units. Detailed LOSVD less-luminous fast rotators with discy isophotes are preferentially measurements for early-type galaxies (e.g. Bender, Saglia & formed through a series of minor mergers with less massive com­ Gerhard 1994; Fisher 1997; Pinkney et al. 2003; Emsellem et al. panions. On the other hand, the more-luminous slow rotators with 2004) have provided us with a general picture of their dynamics. boxy isophotes are thought to form through a violent major merger The higher-order moments are needed to obtain good constraints on between galaxies of similar mass (e.g. Naab, Burkert & Hernquist the anisotropy and mass distribution (Gerhard 1993; Merritt 1993). 1999; Naab & Burkert 2003), or through multiple or hierarchical Most of the studied objects appear to be isotropic or slightly radi­ mergers (Weil & Hernquist 1996; Burkert et al. 2008). ally anisotropic systems (Kronawitter et al. 2000; Cappellari et al. These formation mechanisms are complicated further by the pres­ 2006). Some galaxies have revealed the presence of cold stellar ence or absence of gas during the merger event, which plays a discs whose kinematics stand out only after 1–1.5 Re (Rix, Carollo fundamental role in the final kinematic structure of the merger rem­ & Freeman 1999). nant (e.g. Barnes & Hernquist 1996; Naab, Jesseit & Burkert 2006; Kinematics of early-type galaxies are related to their isopho­ Ciotti, Lanzoni & Volonteri 2007). Mergers producing red-sequence tal shape. Deviations of the isophotes from a perfect ellipse galaxies dominated by rotation appear to be gas-rich (wet), while are parametrized by the amplitude a4 of the cos 4θ term in a gas-poor (dry) mergers produce red-sequence galaxies dominated Fourier expansion of the isophote radius in polar coordinates (e.g. by random motions (e.g. Bournaud, Jog & Combes 2005; Cox et al. Bender, Doebereiner & Moellenhoff 1988). Observational evidence 2006; Naab et al. 2006). (e.g. Bender 1988; Kormendy & Djorgovski 1989) implies that discy However, observations show that many of the most massive early- ellipticals (a4 > 0) have significant rotation with V/σ ≥ 1 and may type galaxies were already in place by z ∼ 2 (van Dokkum et al. generally be axisymmetric; boxy ellipticals (a4 < 0) exhibit no ro­ 2004; Treu et al. 2005), and the evolution of the galaxy luminosity tation, have a range of values of V/σ including strongly anisotropic function since redshifts of z ∼ 1 argues against a significant contri­ systems (V/σ « 1), may be triaxial and are in general more mas­ bution of recent dissipationless dry mergers to the formation of the sive than discy ellipticals. These relations between isophotal shape most massive early-type galaxies in the red sequence (Scarlata et al. and galaxy kinematics motivated Kormendy & Bender (1996) to 2007). Therefore, it is clear that the processes forming elliptical revise the Hubble classification scheme for early-type galaxies us­ galaxies are not yet completely understood. ing the a4 parameter, which is related to intrinsic galaxy properties Numerical simulations of galaxy formation in a cosmological rather than the apparent ellipticity, which is related to the galaxy’s context predict particular radial profiles for the total and dark mat­ orientation on the sky. ter distributions (e.g. Dekel et al. 2005; Naab et al. 2007), for the A related modification to this scheme has been recently pro­ V/σ ratio (e.g. Abadi, Navarro & Steinmetz 2006), the angular mo­ posed by Emsellem et al.
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