Revista mexicana de astronomía y astrofísica

 

Photometry of polar–ring galaxies

 

Arturo Godínez–Martínez,¹ Alan M. Watson,² Lynn D. Matthews,³ and Linda S. Sparke⁴

 

1 Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, México.
A. Godínez–Martínez: Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3–72 (Xangari), 58089 Morelia, Michoacán, México (arturogm@gmail.com).

2 Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, México.
A. M. Watson: Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3–72 (Xangari), 58089 Morelia, Michoacán, México (a.watson@astrosmo.unam.mx).

3 Harvard–Smithsonian Center for Astrophysics, USA.
L. D. Matthews: Harvard–Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA (lmatthew@cfa.harvard.edu).

4 Department of Astronomy, University of Wisconsin–Madison, USA.
L. S. Sparke: Department of Astronomy, University of Wisconsin–Madison, 475 North Charter Street, Madison, WI 53706–1582, USA (sparke@astro.wisc.edu).

 

Received 2007 May 11
Accepted 2007 June 19

 

Resumen

Se obtuvo fotometría en B y R en siete galaxias con anillo polar, probables o confirmadas, del Catálogo de Anillos Polares (PRC) de Whitmore et al. (1990). Los anillos tienen un amplio intervalo de colores de B — R ≈ 0.6 hasta B — R ≈ 1.7. Los anillos más azules contienen brillantes regiones HII, las cuales son evidencia directa de formación estelar reciente. La edad mínima del anillo más rojo, el de PRC B–20, es algo incierta debido a la falta de conocimiento del enrojecimiento interno y la metalicidad en este sistema, pero parece ser al menos de 1.2 Gyr. Por lo tanto, este anillo parece ser estable, al menos durante varios periodos rotacionales. Este anillo es un excelente candidato para estudios futuros que podrán determinar de mejor manera si en realidad es un anillo viejo.

 

Abstract

We have obtained photometry in B and R for seven confirmed or probable polar–ring galaxies from the Polar–Ring Catalog of Whitmore et al. (1990). The rings show a range of colors from B —R ≈ 0.6 to B — R ≈ 1.7. The bluest rings have bright HII regions, which are direct evidence for recent star formation. The minimum age of the reddest ring, that in PRC B–20, is somewhat uncertain because of a lack of knowledge of the internal reddening and metallicity, but appears to be at least 1.2 Gyr. As such, this ring is likely to be stable for at least several rotation periods. This ring is an excellent candidate for future studies that might better determine if it is truly old.

Key Words: Galaxies: halos—galaxies:photometry—galaxies: stellar content

 

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Acknowledgement

We thank Pedro Colín, José Antonio de Diego, Simon Kemp, and Michael Richer for useful comments on an early version of this work. We thank an anonymous referee for a useful report. We are grateful to the staff of the Observatorio Astronómico Nacional on Sierra San Pedro Mártir for their hospitality and technical support during the observing runs. This work has been supported in part by the project IN118302–3 of the UNAM/DGAPA. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

 

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