Calibrating [OII] star-formation rates at z>1 from dual Hα-[OII] imaging from HiZELS

Дата и время публикации : 2012-12-20T01:52:49Z

Авторы публикации и институты :
Masao Hayashi
David Sobral
Philip N. Best
Ian Smail
Tadayuki Kodama

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 10 pages, 7 figures, 1 table, accepted for publication in MNRAS
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO

Краткий обзор статьи: We investigate the relationship between Halpha and [OII](lambda 3727) emission in faint star-forming galaxies at z=1.47 with dust uncorrected star formation rates (SFRs) down to 1.4 Msun/yr, using data in two narrow-bands from WFCAM/UKIRT and Suprime-Cam/Subaru. A stacking analysis allows us to investigate Halpha emission flux from bright [OII] emitters as well as faint ones for which Halpha is not individually detected, and to compare them with a large sample of local galaxies. We find that there is a clear, positive correlation between the average Halpha and [OII] luminosities for [OII] emitters at z=1.47, with its slope being consistent with the local relation. [OII] emitters at z=1.47 have lower mean observed ratios of Halpha/[OII] suggesting a small but systematic offset (at 2.8sigma significance) towards lower values of dust attenuation, A(Halpha)~0.35, than local galaxies. This confirms that [OII] selection tends to pick up galaxies which are significantly less dusty on average than Halpha selected ones, with the difference being higher at z=1.47 than at z=0. The discrepancy of the observed line ratios between [OII] emitters at z=1.47 and the local galaxies may in part be due to the samples having different metallicities. However, we demonstrate that metallicity is unlikely to be the main cause. Therefore, it is important to take into account that the relations for the dust correction which are derived using Halpha emitter samples, and frequently used in many studies of high-z galaxies, may overestimate the intrinsic SFRs of [OII]-selected galaxies, and that surveys of [OII] emission galaxies are likely to miss dusty populations.

Category: Physics