ACS UDF Parallels - ACS HRC

The ST-ECF is managing the processing of ACS HRC Parallels. The two pairs of overlapping fields both fall mainly in the GOODS-South field.

ACS/HRC Scientific Rationale:

The ACS High Resolution Channel (HRC) offers the possibility to obtain auto-parallels when the WFC is prime. Since the Wide Field Channel (WFC) and the HRC share the same filter wheels, the filter in use by WFC dictates the HRC filter. For the HUDF observations HRC auto-parallels have been obtained with the F220W, F555W and F892N filters and the G800L grism. The scientific aim is to obtain complementary deep images at a spatial resolution about twice that of the WFC over a smaller field. The pixel size is 0.027arcsec so the sensitivity to compact sources is higher than for WFC. The F555W images will provide a deep V band image; the F220W although not very sensitive will provide a UV colour which may be interesting for the UV morphology of nearby galaxies and low-moderate redshift objects (z~<2). The F892N filter is narrow (150A) but is of interest for detecting emission line objects in a narrow range, such as [O II] emitters 1.37<z<1.41 and ly-alpha objects 6.27<z<6.40 very red continuum objects. the g800l grism provides slitless spectra at a dispersion of 24a pixel but resolution depends size dispersing object. coverage is 5500-10500a with peak sensitivity about 7500a. continuous wavelength in makes it competitive for deep spectroscopy compared ground small pixels make hrc relatively more sensitive than wfc. 40000s, useful (>2sigma per resolution element) spectra of continuum objects with V fainter than 27.0 can be obtained.

ACS/HRC Pointing:

Very approximate coordinates for the 2 pairs of ACS HRC parallels are:

Epoch 1, ORIENT 310  RA (J2000)= 03 32 54.4    DEC (J2000)= -27 49 07.3 ~center

Epoch 1, ORIENT 314  RA (J2000)= 03 32 53.8    DEC (J2000)= -27 49 21.8 ~center


Epoch 2, ORIENT  40  RA (J2000)= 03 32 31.6    DEC (J2000)= -27 50 52.1 ~center

Epoch 2, ORIENT  44  RA (J2000)= 03 32 30.5    DEC (J2000)= -27 50 45.0 ~center

ACS/HRC Filters:

ACS/HRC autoparallel filters are automatically determined by the ACS/WFC primary filter in use. The UDF filter pairings are below:

ACS/HRC Depth:

The limiting magnitude estimates below were calculated using the ACS ETC. As specified for the ACS/WFC exposures, the calculations are for a S/N of 10 within a 0.2 sq arcsec aperture (15x15 HRC pixels) and average zodiac and earthshine.

Limiting AB magnitudes for S/N = 10 in 15x15 pixels aperture.

Epoch 1:

Epoch 2:

ACS/HRC Status:

All data for both Epochs have been obtained.