Seeing the Unvierse at redshift one with the AAT and CIRPASS: a multi-object near-infrared spectrograph
Abstract
We present preliminary results from the CIRPASS instrument (Parry et al. 2000 SPIE 4008, 1193) -- a near-infrared fiber-fed spectrograph which was successfully commissioned in its multi-object spectroscopy (MOS) mode on the 4-m Anglo Australian Telescope in October 2002. The high resolving power of λ / Δ λFWHM≈ 5000 enables us to work effectively in the low-background regions between the OH sky lines in the J- and H-bands (1.0-1.7 μ m). CIRPASS-MOS has 150 fibres each of 1.6'' diameter, deployable over a 40'-wide area. A natural project for CIRPASS-MOS is tracing star formation at z ∼ 1 using robust indicators such as Hα , redshifted into the near-infrared. We demonstrated this capability in our AAT observations last October, by observing some galaxies from the Calar Alto Deep Imaging Survey (CADIS) selected from a narrow redshift interval at z=0.88 by their [Oriptsize II] 3727 Å line emission observed in extensive Fabry-Perot observations (Hippelein et al. 2003, astro-ph/0302116). The Hα is found at ≈ 1.247 μ m in a very clean (OH line-free) region of the night-sky spectrum, and we were able to detect Hα for a number of these galaxies. We demonstrated that CIRPASS achieved its design sensitivity: in a stacked 12-hour exposure we detected lines as faint as 4x 10-17 ergs cm-2 s-1 at 10 σ (for Δ vFWHM ∼ 300 km/s). This corresponds to an Hα flux at z ∼ 1 equivalent to an unobscured star formation rate of 2 h70-2 Msun yr-1 at z=1 (Ω M=0.3, Ω Λ =0.7), comparable to the star formation rate of the Milky Way today. We also successfully targeted a number of galaxies with photometric redshifts z ∼ 1, and broad-band colours indicating star formation. We are currently installing a 2kx 2k detector on CIRPASS, which will double the wavelength coverage to 2100 Å , and hence our ability to successfully target photometrically-selected galaxies over a range of redshifts will be greatly increased.
- Publication:
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American Astronomical Society Meeting Abstracts #202
- Pub Date:
- May 2003
- Bibcode:
- 2003AAS...202.1111P