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Home List of Titles A dual-narrowband survey for H alpha emitters at redshift of 2.2: demonstration of the technique and constraints on the H alpha luminosity function
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/232910
- A dual-narrowband survey for H alpha emitters at redshift of 2.2: demonstration of the technique and constraints on the H alpha luminosity function
- Lee, Janice C.; Ly, Chun; Spitler, Lee; Labbe, Ivo; Salim, Samir; Persson, S. Eric; Ouchi, Masami; Dale, D. A.; Monson, A.; Murphy, D.
- We present first results from a narrowband imaging program for intermediate-redshift emission-line galaxies using the newly commissioned FourStar infrared camera at the 6.5 m Magellan telescope. To enable prompt identification of Hα emitters, a pair of custom 1% filters, which sample low-airglow atmospheric windows at 1.19 μm and 2.10 μm, is used to detect both Hα and [O II] λ3727 emission from the same redshift volume at z = 2.2. Initial observations are taken over a 130 arcmin2 area in the CANDELS-COSMOS field. The exquisite image quality resulting from the combination of the instrument, telescope, and standard site conditions (∼0.55′′ FWHM) allows the 1.19 μm and 2.10 μm data to probe 3σ emission-line depths down to 1.0 × 10-17 erg s-1 cm-2 and 1.2 × 10-17 erg s-1 cm-2, respectively, in less than 10 hr of integration time in each narrow band. For Hα at z = 0.8 and z = 2.2, these fluxes correspond to observed star formation rates of ∼0.3 and ∼4 M⊙ yr-1, respectively. We find 122 sources with a 1.19 μm excess and 136 with a 2.10 μm excess, 41 of which show an excess in both bands. The dual-narrowband technique, as implemented here, is estimated to identify ≳80% of z = 2.2 Hα emitters in the narrowband excess population. With the most secure such sample obtained to date, we compute constraints on the faint-end slope of the z = 2.2 Hα luminosity function. Fitting of a pure power law gives α = -1.85 ± 0.31, which is steeper than other recent estimates based on coarser selection techniques, but consistent within the typically large uncertainties that currently characterize such measurements. Combining our LF points with those at higher luminosities from other work, the slope decreases to α = -1.58 ± 0.40. These “narrow-deep& 8221; FourStar observations have been obtained as part of the larger New Hα Survey, which will combine the data with “wide-shallow” imaging through a similar narrowband filter pair with NEWFIRM at the KPNO/CTIO 4 m telescopes, to enable study of both luminous (but rare) and faint emission-line galaxies in the intermediate-redshift universe.
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing
- Publications of the Astronomical Society of the Pacific, Vol. 124, no. 917 (Jul 2012), pp. 782-797
- Publication year
- FOR Code(s)
- 0201 Astronomical and Space Sciences
- Emission-line galaxies; FourStar observations; Luminosity function; Narrowband imaging; Redshifts
- University of Chicago Press
- Publisher URL
- Copyright © 2012. The Astronomical Society of the Pacific.
- Peer reviewed