Bar pattern speeds in CALIFA galaxies

I. Fast bars across the Hubble sequence

¹ Instituto de Astrofísica de Canarias. C/ Vía Láctea s/n, 38200 La Laguna, Spain
e-mail: jalfonso@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
³ School of Physics and Astronomy, University of St Andrews, North Haugh, St. Andrews, KY16 9SS, UK
⁴ Departamento de Fisica, Universidade Federal de Santa Catarina, PO Box 476, 88040-900 Florianópolis, S C, Brazil
⁵ Instituto de Astrofísica de Andalucía – CSIC, 18008 Granada, Spain
⁶ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁷ Max-Planck-Institut für Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany
⁸ CEI Campus Moncloa, UCM-UPM, Departamento de Astrofísica y CC. de la Atmósfera, Facultad de CC. Físicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain
⁹ Instituto de Cosmologia, Relatividade e Astrofísica – ICRA, Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, CEP 22290-180, Rio de Janeiro, RJ, Brazil
¹⁰ Centro Astronómico Hispano Aleman, Calar Alto (CSIC-MPG), C/ Jesús Durbán Remón 2-2., 04004 Almeria, Spain
¹¹ Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia
¹² Dpto. de Física Teórica y del Cosmos, University of Granada, Facultad de Ciencias (Edificio Mecenas), 18071 Granada, Spain
¹³ Instituto Universitario Carlos I de Física Teórica y Computacional, Facultad de Ciencias, 18071 Granada, Spain
¹⁴ Departamento de Fisica Teorica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
¹⁵ University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria

Received: 8 January 2014
Accepted: 7 January 2015

Abstract

Context. The bar pattern speed (Ω_b) is defined as the rotational frequency of the bar, and it determines the bar dynamics. Several methods have been proposed for measuring Ω_b. The non-parametric method proposed by Tremaine & Weinberg (1984, ApJ, 282, L5; TW) and based on stellar kinematics is the most accurate. This method has been applied so far to 17 galaxies, most of them SB0 and SBa types.

Aims. We have applied the TW method to a new sample of 15 strong and bright barred galaxies, spanning a wide range of morphological types from SB0 to SBbc. Combining our analysis with previous studies, we investigate 32 barred galaxies with their pattern speed measured by the TW method. The resulting total sample of barred galaxies allows us to study the dependence of Ω_b on galaxy properties, such as the Hubble type.

Methods. We measured Ω_b using the TW method on the stellar velocity maps provided by the integral-field spectroscopy data from the CALIFA survey. Integral-field data solve the problems that long-slit data present when applying the TW method, resulting in the determination of more accurate Ω_b. In addition, we have also derived the ratio ℛ of the corotation radius to the bar length of the galaxies. According to this parameter, bars can be classified as fast (ℛ < 1.4) and slow (ℛ > 1.4).

Results. For all the galaxies, ℛ is compatible within the errors with fast bars. We cannot rule out (at 95% level) the fast bar solution for any galaxy. We have not observed any significant trend between ℛ and the galaxy morphological type.

Conclusions. Our results indicate that independent of the Hubble type, bars have been formed and then evolve as fast rotators. This observational result will constrain the scenarios of formation and evolution of bars proposed by numerical simulations.