Spatially resolved properties of the grand-design spiral galaxy UGC 9837: a case for high-redshift 2-D observations

¹ Centro Astronómico Hispano Alemán, C/ Jesús Durbán Remón 2-2, 04004 Almeria, Spain
e-mail: kerttu@cefca.es
² Centro de Estudios de Física del Cosmos de Aragón (CEFCA), C/ Pizarro 1, 3 a, 41001 Teruel, Spain
³ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁴ Departamento de Astrofísica y CC. de la Atmósfera, Universidad Computense de Madrid, 28040 Madrid, Spain
⁵ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁶ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Postdam, Germany

Received: 17 December 2010
Accepted: 22 November 2011

Abstract

Context. We carry out a detailed 2-D study of the ionised gas in the local universe galaxy UGC 9837. In nearby galaxies, like the galaxy in question here, the spatial distribution of the physical properties can be studied in detail, providing benchmarks for galaxy formation models.

Aims. Our aim is to derive detailed and spatially resolved physical properties of the ionised gas of UGC 9837. In addition, we derive an integrated spectrum of the galaxy and study how varying spatial coverage affects the derived integrated properties. We also study how the same properties would be seen if the galaxy was placed at a higher redshift and observed as part of one of the high-z surveys.

Methods. UGC 9837 was observed using the PMAS PPAK integral-field unit. The spectra were reduced and calibrated and the stellar and ionised components separated. Using strong emission line ratios of the ionised gas, the source of ionisation, the dust extinction, the star formation rate, the electron density, and the oxygen abundance derived from a total integrated spectrum, central integrated spectrum, and individual fibre spectra are studied. Finally, the same properties are studied in a spectrum whose spatial resolution is degraded to simulate high-z observations.

Results. The spatial distribution of the ionised gas properties is consistent with inside-out growing scenario of galaxies. We also find that lack of spatial coverage would bias the results derived from the integrated spectrum leading, e.g., to an underestimation of ionisation and overestimation of metallicity, if only the centre of the galaxy was covered by the spectrum. Our simulation of high-z observations shows that part of the spatial information, such as dust and SFR distribution would be lost, while shallower gradients in metallicity and ionisation strength would be detected.