NIRI SV observation 1

	Status: in preparation Data link: not yet available Assessment: not yet available

Mode:	Low-background broadband imaging
Additional instrument verification:	Data reduction pipeline for imaging data; characterization of array noise performance, spatial flatness, and residual image persistance; characterization of the point spread function consistency throughout the field.
Telescope verification:	Acquisition and guiding on object with NIRI; repeated offsetting of telescope to perform sky subtraction; use of PWFS and OIWFS sequenced with telescope offsets
Proposed observing sequence:	Individual exposures on a galaxy will be dithered to improve flat-fielding and correction of bad pixels. Offset to sky positions between object exposures and dither the sky measurements as well. Observations of standard stars are required to calibrate the photometry.
OT program file:	Not yet available
Science background:	IR Surface Brightness Flucutation Distance Measurements We propose to demonstrate the ability to measure accurate IR surface brightness fluctuation (SBF) distances beyond 100 Mpc using NIRI. General agreement on the value of the Hubble constant (Ho) is emerging, yet there are still significant systematic differences between individual techniques. SBFs have been shown to produce accurate distances. We seek to extend the IR SBF distance scale as a step towards measuring Ho on scales of 10,000 km/s. We will exploit the excellent image quality, large aperture, and relatively wide field of view Gemini offers to construct the IR SBF Hubble diagram by measuring SBFs in some relatively nearby calibration galaxies and then measuring distances to several galaxies out to ~10,000 km/s. These measurements will allow us to determine Ho with an accuracy better than 10% at distances large enough to be free of local streaming motions. This project will establish IR SBFs as an accurate distance measurement tool beyond 10,000 km/s and is well-suited to testing telescope and instrument performance.
Target(s):
	Object	approx. RA (2000)	approx. dec (2000)	cz (km/s)
	Abell 779 (N2832)	09:19:47	+33:44:58	6796
	Abell 1177	11:09:45	+21:45:32	9561
	Abell 1367 (N3842)	11:44:02	+19:56:59	6237
	NGC 4493	12:31:09	+00:36:48	6943
	ESO507G045	12:55:36	-26:49:26	4875
	Abell 1656 (N4889)	13:00:08	+27:58:36	6497
	Abell 2063	15:23:06	+08:36:33	10626
	Abell 2199 (N6166)	16:28:38	+39:33:04	9034
	Calibrators:
	N3379, 3384, 3368, 3351	10:46	+12	(Leo)
	N4472, 4406, 4434, 4458	12:30	+08, +12	(Virgo)

Observing condition constraints:	image quality: 50%-ile sky transparency (clouds): 50%-ile sky transparency (water vapour): Any sky background: 80%-ile max air mass: 1.5
Observing time requirements:	The exposure time required varies with distance and image quality. With 0.5 arcsec seeing, a galaxy at 6000 km/s requires 1700 s on-source and a galaxy at 10,000 km/s requires 4700 s. When the seeing is 0.3 arcsec, the integration time will be 1000 s for a galaxy at 6000 km/s and 2800 s for a galaxy at 10,000 km/s. Thus if the 6000 km/s galaxies are all observed at 0.5 arcsec and the 10,000 km/s galaxies at 0.3, the total time required for this project would be 12 hours, including time for sky measurements and overhead. Calibration galaxies require less than 2 minutes each.
SV team member(s) responsible for assessment:	Joe Jensen

Last update October 29, 1999; Joe Jensen