WFC3IR Minimum Exposure Times and Subarrays

WFC3/IR is a multi-accum detector. There are many timing sequences, with the possibility of using 1 to 15 reads for each. The total integration time depends on the type of timing sequence, the number of reads (NSAMP), and the size of the selected array. Subarrays have shorter integration times than full arrays for the same timing sequence name. The integration times are shown in tables in the Phase II Proposal Instructions.

The read noise depends on the NSAMP. The ETC uses a value of read noise that assumes NSAMP=15. It underestimates the read noise for smaller NSAMP. The ETC accepts or computes only a total integration time, so observers should check the possible integration times and keep in mind the assumption of NSAMP=15 for the read noise.

WFC3 Filters and Dispersers

The following tables show the filter and disperser properties.

WFC3 UVIS Filters and Grism

Name [1] Description [2] Pivot (A) [3] Width (A) [4] Peak Transmission
UVIS Long-Pass (LP) and Extremely Wide (X) Filters
F200LP Clear; grism reference 5686.9
0.98
F300X Extremely wide UV 2829.8 753.0 0.53
F350LP Long pass 6812.0
0.98
F475X Extremely wide blue 4917.1 2199.6 0.94
F600LP Long pass 8430.2
0.99
F850LP SDSS z 9756.4
0.96
UVIS Wide-Band(W) Filters
F218W ISM feature 2183.0 351.7 0.23
F225W UV wide 2341.0 547.3 0.32
F275W UV wide 2715.3 480.8 0.46
F336W U, Stromgren u 3361.1 553.8 0.75
F390W Washington C 3904.6 953.0 0.96
F438W WFPC2 B 4318.7 676.8 0.84
F475W SDSS g 4760.6 1488.9 0.92
F555W WFPC2 V 5309.8 1595.1 0.95
F606W WFPC2 Wide V 5907.0 2304.2 0.99
F625W SDSS r 6254.0 1575.4 0.95
F775W SDSS i 7733.6 1486.0 0.85
F814W WFPC2 Wide I 8304.7 2543.3 0.97
UVIS Medium-Band (M) Filters
F390M Ca II continuum 3893.8 210.5 0.88
F410M Stromgren v 4107.0 182.8 0.98
FQ422M Blue continuum 4217.7 113.3 0.69
F467M Stromgren b 4680.7 218.0 0.98
F547M Stromgren y 5447.0 714.0 0.88
F621M 11% passband 6216.7 631.0 0.99
F689M 11% passband 6886.0 708.6 0.94
F763M 11% passband 7636.3 798.6 0.97
F845M 11% passband 8468.9 886.7 0.96
UVIS Narrow-Band (N) Filters
FQ232N C II] 2326 2326.9 32.2 0.12
FQ243N [Ne IV] 2425 2420.6 34.8 0.15
F280N Mg II 2795/2802 2796.8 22.9 0.27
F343N [Ne V] 3426 3438.0 140.0 0.78
F373N [O II] 3726/3728 3729.6 39.2 0.78
FQ378N z ([O II] 3726) 3790.9 89.2 0.83
FQ387N [Ne III] 3868 3873.0 23.1 0.72
F395N Ca II 3933/3968 3953.7 72.9 0.86
FQ436N H 4340 + [O III] 4363 4366.7 35.7 0.67
FQ437N [O III] 4363 4370.6 24.6 0.70
F469N He II 4686 4687.5 37.2 0.69
F487N H 4861 4870.7 48.4 0.85
FQ492N z (H) 4932.1 101.0 0.85
F502N [O III] 5007 5009.0 57.8 0.87
FQ508N z ([O III] 5007) 5089.7 117.9 0.87
FQ575N [N II] 5754 5755.9 12.9 0.78
FQ619N CH4 6194 6197.5 61.6 0.89
F631N [O I] 6300 6303.0 43.1 0.86
FQ634N 6194 continuum 6347.5 66.2 0.88
F645N Continuum 6451.6 85.0 0.86
F656N H 6562 6561.1 13.9 0.86
F657N Wide H + [N II] 6565.1 96.3 0.90
F658N [N II] 6583 6585.2 23.6 0.92
F665N z (H + [N II]) 6654.4 109.0 0.90
FQ672N [S II] 6717 6716.1 14.9 0.89
F673N [S II] 6717/6731 6764.5 100.5 0.91
FQ674N [S II] 6731 6729.5 10.0 0.68
F680N z (H + [N II]) 6878.6 323.6 0.95
FQ727N CH4 7270 7274.7 64.8 0.89
FQ750N 7270 continuum 7500.6 68.8 0.85
FQ889N CH4 25 km-agt [5] 8891.8 93.7 0.90
FQ906N CH4 2.5 km-agt 9056.7 94.0 0.92
FQ924N CH4 0.25 km-agt 9246.3 89.2 0.94
FQ937N CH4 0.025 km-agt 9371.1 91.9 0.91
F953N [S III] 9532 9529.7 84.6 0.90
UVIS Grism (G)
G280 UV Grism
1850 0.4
[1]The spectral-element naming convention is as follows for both the UVIS and IR channels. All filter names begin with F, and grisms with G; if the filter is part of a four-element quad mosaic, a Q follows F. Then there is a three-digit number giving the nominal effective wavelength of the bandpass, in nm (UVIS channel) or nm/10 (IR channel). (For long-pass filters, the number is instead the nominal blue cut-off wavelength in nm.) Finally, for the filters, one or two letters indicate the bandpass width: X (extremely wide), LP (long pass), W (wide), M (medium), or N (narrow).
[2]Filters intended for imaging in a red-shifted bandpass are given descriptions similar to the following: “z (H + [N II])”.
[3]“Pivot wavelength” is a measure of the effective wavelength of a filter (see A. Tokunaga & W. Vacca 2006, PASP, 117, 421). It is calculated here based only on the filter transmission. Values are approximate for the long-pass filters. All wavelength measurements in this table were made in air.
[4]Full width at 50% of peak transmission for wide and medium bands, and at 10% of peak transmission for narrow bands. For long-pass filters, the widths are approximate and include convolution with the detector QE.
[5]km-agt (km-amagat) is a unit of vertical column density, equal to 2.69e24 molecules/cm^2

WFC3 IR Channel Filters and Grisms

Name [6] Description Pivot [7] (nm) Width [8] (nm) Peak Transmission
IR Wide-Band(W) Filters
F105W Wide Y 1048.95 292.30 0.98
F110W Wide YJ 1141.40 503.40 0.99
F125W Wide J 1245.90 301.50 0.98
F140W Wide JH gap; red grism reference 1392.10 399.00 0.99
F160W WFC3 H 1540.52 287.88 0.98
IR Medium-Band(M) Filters
F098M Blue grism reference 982.93 169.48 0.97
F127M H2O/CH4 continuum 1273.64 68.79 0.98
F139M H2O/CH4 line 1383.80 64.58 0.98
F153M H2O and NH3 1533.31 68.78 0.98
IR Narrow-Band(N) Filters
F126N [Fe II] 1258.26 11.83 0.90
F128N Paschen 1283.30 13.54 0.94
F130N Paschen continuum 1300.62 13.28 0.96
F132N Paschen (redshifted) 1319.04 13.07 0.91
F164N [Fe II] 1645.13 17.48 0.93
F167N [Fe II] continuum 1667.26 17.16 0.93
IR Grisms (G)
G102 “Blue” high-resolution grism
250
G141 “Red” low-resolution grism
600
[6]See Footnote 1 of UVIS table for naming conventions.
[7]“Pivot wavelength” is defined as in Table 6.2. All wavelength measurements in this table were made in air.
[8]Full width at 50% of peak transmission.