title: The growth of the central region by acquisition of counterrotating gas in star-forming galaxies.
abstract: Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars.
authors.affiliation: School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China.|Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, China.|Collaborative Innovation Center of Modern Astronomy and Space Exploration, Nanjing 210093, China.
authors.forename: Yan-Mei
authors.initials: YM
authors.lastname: Chen
authors.affiliation: School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China.|Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, China.|Collaborative Innovation Center of Modern Astronomy and Space Exploration, Nanjing 210093, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Astronomy, University of Wisconsin-Madison, 1150 University Ave, Madison,Wisconsin 53706, USA.
authors.forename: Christy A
authors.initials: CA
authors.lastname: Tremonti
authors.affiliation: Department of Astronomy, University of Wisconsin-Madison, 1150 University Ave, Madison,Wisconsin 53706, USA.
authors.forename: Matt
authors.initials: M
authors.lastname: Bershady
authors.affiliation: School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Merrifield
authors.affiliation: European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany.|Université Lyon 1, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon and Ecole Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis Laval, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Emsellem
authors.affiliation: School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China.|Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, China.|Collaborative Innovation Center of Modern Astronomy and Space Exploration, Nanjing 210093, China.
authors.forename: Yi-Fei
authors.initials: YF
authors.lastname: Jin
authors.affiliation: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8583, Japan.
authors.forename: Song
authors.initials: S
authors.lastname: Huang
authors.affiliation: Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Hai
authors.initials: H
authors.lastname: Fu
authors.affiliation: Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Wake
authors.affiliation: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8583, Japan.
authors.forename: Kevin
authors.initials: K
authors.lastname: Bundy
authors.affiliation: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8583, Japan.
authors.forename: David
authors.initials: D
authors.lastname: Stark
authors.affiliation: Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan.
authors.forename: Lihwai
authors.initials: L
authors.lastname: Lin
authors.affiliation: Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030, China.|Universidad de Antofagasta, Unidad de Astronoma, Facultad Cs. Bsicas, Av. U. de Antofagasta, 02800 Antofagasta, Chile.
authors.forename: Maria
authors.identifier: 0000-0002-0789-2326
authors.initials: M
authors.lastname: Argudo-Fernandez
authors.affiliation: Departamento de Astronomia, Instituto de Física, Universidade Federal do Rio Grande do Sul, CP 15051, 91501-970, Porto Alegre, RS, Brazil.|Laboratório Interinstitucional de e-Astronomia-LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil.
authors.forename: Thaisa Storchi
authors.initials: TS
authors.lastname: Bergmann
authors.affiliation: Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, New Mexico 88349-0059, USA.|Sternberg Astronomical Institute, Moscow State University, Moscow 119899, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Bizyaev
authors.affiliation: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Brownstein
authors.affiliation: Sub-Department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Bureau
authors.affiliation: Department of Astronomy, University of Wisconsin-Madison, 1150 University Ave, Madison,Wisconsin 53706, USA.
authors.forename: John
authors.initials: J
authors.lastname: Chisholm
authors.affiliation: Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA.
authors.forename: Niv
authors.initials: N
authors.lastname: Drory
authors.affiliation: National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang, Beijing 10012, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Hao
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, China.|Center for Astrophysics, Tsinghua University, Beijing 100084, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, China.|Center for Astrophysics, Tsinghua University, Beijing 100084, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Li
authors.affiliation: National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang, Beijing 10012, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Li
authors.affiliation: Departamento de Fsica, Facultad de Ciencias, Universidad de La Serena, Cisternas 1200, La Serena, Chile.
authors.forename: Alexandre Roman
authors.initials: AR
authors.lastname: Lopes
authors.affiliation: Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, New Mexico 88349-0059, USA.
authors.forename: Kai-Ke
authors.initials: KK
authors.lastname: Pan
authors.affiliation: Laboratório Interinstitucional de e-Astronomia-LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil.|Departamento de Física, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil.
authors.forename: Rogemar A
authors.initials: RA
authors.lastname: Riffel
authors.affiliation: Institute for Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomas
authors.affiliation: National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang, Beijing 10012, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Institute for Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX, UK.
authors.forename: Kyle
authors.initials: K
authors.lastname: Westfall
authors.affiliation: Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA.
authors.forename: Ren-Bin
authors.initials: RB
authors.lastname: Yan