Below are my aperature photometry measurements as compared with Boissier et al (2008). To estimate the light coming from knots, the pixels with intensity > 2.576 sigma were masked out before calculating colors. The column titles in parentheses refer to the second row.
| Galaxy (Knot Photometry) | UV Image (Knots Masked Image) | Optical Image ("Diffuse" fraction of total light NUV) | Susco NUV AB magnitude ("Diffuse" fraction of total light FUV) | Susco FUV AB magnitude | Susco UV color (Entire aperature) | Boissier et al. NUV AB magnitude ("Diffuse" color) | Boissier et al. FUV AB magnitude (Knots only color) | Boissier et al. UV color |
|---|---|---|---|---|---|---|---|---|
| F563-1 | |
|
17.01 +/- 0.05 | 17.33 +/- 0.04 | 0.3210 +/- 0.06 | n/a | n/a | n/a |
| Knot photometry: | |
0.7760 | 0.7943 | 0.3210 | 0.2957 | 0.4137 | ||
| F565-V2 | |
|
19.35 +/- 0.03 | 19.56 +/- 0.12 | 0.2110 +/- 0.12 | n/a | n/a | n/a |
| Knot photometry: | |
0.9349 | 0.9206 | 0.2110 | 0.2277 | -0.0049 | ||
| F568-1 | |
|
17.88 +/- 0.11 | 18.25 +/- 0.03 | 0.3689 +/- 0.11 | 17.76 +/- 0.02 | 18.16 +/- 0.03 | 0.40 +/- 0.036 |
| Knot photometry: | |
0.9415 | 0.9206 | 0.3689 | 0.4156 | -0.1925 | ||
| F568-3 | |
|
17.60 +/- 0.07 | 17.84 +/- 0.04 | 0.2374 +/- 0.08 | 17.49 +/- 0.02 | 17.80 +/- 0.03 | 0.31 +/- 0.036 |
| Knot photometry: | |
0.8960 | 0.8825 | 0.2374 | 0.2539 | 0.1049 | ||
| UGC 1195 | |
|
14.72 +/- 0.01 | 15.02 +/- 0.01 | 0.3018 +/- 0.02 | n/a | n/a | n/a |
| Knot photometry: | |
0.8492 | 0.8471 | 0.3018 | 0.3045 | 0.2866 | ||
| UGC 4325 | |
|
14.15 +/- 0.01 | 14.32 +/- 0.01 | 0.1660 +/- 0.02 | n/a | n/a | n/a |
| Knot photometry: |
| 0.9011 | 0.8765 | 0.1660 | 0.196 | -0.0747 | ||
| UGC 5750 | |
|
17.22 +/- 0.03 | 17.53 +/- 0.03 | 0.3113 +/- 0.05 | 17.09 +/- 0.01 | 17.41 +/- 0.01 | 0.32 +/- 0.014 |
| Knot photometry: |
| 0.8773 | 0.8685 | 0.3113 | 0.3223 | 0.2359 | ||
| UGC 891 | |
|
16.12 +/- 0.04 | 16.38 +/- 0.03 | 0.2602 +/- 0.05 | n/a | n/a | n/a |
| Knot photometry: |
| 0.8793 | 0.8635 | 0.2602 | 0.2799 | 0.1266 | ||
| UGC 128 | |
|
16.39 +/- 0.04 | 16.59 +/- 0.11 | 0.2078 +/- 0.11 | n/a | n/a | n/a |
| Knot photometry: |
| 0.8934 | 0.8530 | 0.2078 | 0.2581 | -0.1416 | ||
| UGC 1551 | |
|
14.86 +/- 0.01 | 15.16 +/- 0.01 | 0.2931 +/- 0.02 | n/a | n/a | n/a |
| Knot photometry: |
| 0.9161 | 0.8968 | 0.2931 | 0.3163 | 0.06791 | ||
| UGC 2684 | |
|
16.84 +/- 0.05 | 17.04 +/- 0.11 | 0.1981 +/- 0.12 | n/a | n/a | n/a |
| Knot photometry: |
| 0.8895 | 0.8676 | 0.1981 | 0.2252 | 0.0017 | ||
| Mean and sigma for knot photometry | 0.8978 +/- 0.0275 | 0.8777 +/- 0.0229 | 0.2555 +/- 0.0627 | 0.2799 +/- 0.0632 | 0.0409 +/- 0.1546 |
Note: Boissier et al. did not explicitly list their values for color. I have calculated these and error propagation.
Using the values measured above the following plots were produced. For all galaxies available, SDSS photometry was used. UGC891 and UGC 2684 were plotted using converted g band photometry, B and V band photometry coming from LEDA. UGC 128 and UGC 1551 are not plotted for lack of reliable photometry data. SFR for the F-galaxies came from Hunter et al. (2004) and the UGC galaxies from P.A. James et al . (2004).
![[TXT]](sdssplot.jpg)
fig. 1
fncolor- far minus near UV, this follows for the other bands.
M - absolute magnitude.
SFR - star formation rate.