Repeatibility Tests

T. Jarrett, IPAC
(000517) revised: 010313

Galworks V3.0 Modification Tests

Go to summary report

Three major data sets are considered: repeats of the Abell 3558 galaxy cluster, repeats of the ChamI cloud complex and repeats of the Orion GMC core.

Repeat tests will include the following parameters:

We treat sources that are "contaminated" separately from sources that are "clean". Contamination means that the photometry flags are tripped (non-zero), indicating that another source is nearby and was masked accordingly (with isophotal substitution to recover the lost flux).

We apply the Gscore threshold = 1.4 as the primary star-galaxy discriminant.

Abell 3558 (typical stellar density = 3.1)

A number of repeat scans were acquired during the month of April 2000 to complement the set taken in March of 1998. Here is what I have compiled:

The total area is depicted with this Areal Coverage plot. The scan-scan overlaps of the Abell 3558 core were repeated over 30 times, while the outskirts and most of the cluster area were covered over 15 times; hence, there is more than enough repeats to provide excellent statistics.

Note: I have eliminated inscan duplicates (which are meaningless for these tests); but I have included scan-to-scan dupes (which are meaningful).

RESULTS

Summary Table of Nominal GALWORKS V2 Results

-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2023 2180 0.93 1269 1536 0.826
H7_comp_1.tbl 13.70 14.20 1075 1193 0.90 658 795 0.828
K7_comp_1.tbl 13.00 13.50 1277 1276 1.00 449 514 0.874
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 93 14.47 0.069 52 14.48 0.076
H7_repeats_1.tbl 13.70 14.20 51 13.97 0.105 25 13.94 0.110
K7_repeats_1.tbl 13.00 13.50 62 13.24 0.095 18 13.24 0.098
Jf20e_repeats_1.tbl 14.00 15.00 83 14.50 0.079 55 14.48 0.098
Hf20e_repeats_1.tbl 13.70 14.20 44 13.97 0.105 24 13.95 0.122
Kf20e_repeats_1.tbl 13.00 13.50 59 13.24 0.123 18 13.20 0.132
Jf20c_repeats_1.tbl 14.00 15.00 83 14.47 0.075 58 14.46 0.089
Hf20c_repeats_1.tbl 13.70 14.20 44 13.96 0.110 31 13.94 0.116
Kf20c_repeats_1.tbl 13.00 13.50 55 13.24 0.113 22 13.21 0.130
RKf0e_repeats_1.tbl 10.00 20.00 30 12.02 1.607 47 13.26 1.706
RKf0c_repeats_1.tbl 10.00 20.00 9 12.42 1.452 35 12.69 1.632
J_ba_repeats_1.tbl 0.20 0.80 28 0.49 0.061 75 0.55 0.075
K_ba_repeats_1.tbl 0.20 0.80 30 0.52 0.068 84 0.57 0.096
S_ba_repeats_1.tbl 0.20 0.80 27 0.47 0.054 77 0.55 0.061
J20e_Jext_repeats_1.0.01 0.80 89 0.32 0.115 104 0.35 0.114
H20e_Hext_repeats_1.0.01 0.80 76 0.31 0.119 83 0.32 0.119
K20e_Kext_repeats_1.0.01 0.80 49 0.29 0.116 52 0.27 0.106

TEST #1

Injecting the Calmon zero-point mags into GALWORKs.

TEST #2

Improved Large Galaxy Processing

TEST #3

Coverage Masks and Off-scan JCAT Improvement

For some examples of the new coverage masks, click here.

The JCAT improvement included less stringent masking from JCAT stars off-scan (adjacent scans). Only JCATS brighter than 4th mag (J) are considered. Results in better coverage. Note the increased number of sources (see table below).

TEST #4

Conversion to SNR Thresholds

GALWORKS V2 used mag thresholds to ignore faint sources. The modification is to use an SNR threshold instead, using a fixed circular aperture measurement. Since a 7" radius appears to be a natural size limit for most galaxies (i.e., faint ones), we compute the SNR from this aperture. The SNR threshold itself should approximately match the original mag thresholds. This turns out to be a value of 5:1.

SNR Threshold: 5:1

Detection Repeatibility
white points are uncontaminated; green points are contaminated; red points are false extended sources (usually double stars)

TEST #5

Removing Known (Large) Galaxy Bias

GALWORKS V2 used a "seed" catalog of known, large (diam>1') galaxies to assist the processor. These sources were processed and passed into the DB regardless of their flux and scores. The new modification removes this bias. These galaxies are now processed the same as non-catalogued galaxies. They are subject to the same star-galaxy discrimination scores.

Note: With this modification, the problem of galaxy blending will only get worse since we now do not force processing on known galaxies. V3, by design, should now include large galaxies that have eaten their neighboring companions.

Big BIG Galaxies

Galaxies are a little bigger to 2MASS now. Previously we resricted processing to galaxies with sizes < 5' or so. Now we work on everything. As discussed earlier, what makes this possible is by using the "scan" background (fit over the background) instead of the coadd backgroud for those coadds affected by the big galaxies. In addition, the working "area" has been increased from 80" radius to 120" radius. Correspondingly, the postage stamps images are now larger for the larger objects, with a maximum size now set at 5'.

Some examples are given below, including M31, M32, M33, M51 and a sextet group of galaxies. The downside of including these galaxies is that there is a lot of "debris" surrounding the galaxies (some examples given below). The reliability is in question near the largest galaxies (see M31).

Improved Star Subtraction

Goal: by improving the subtraction of neighboring stars, the photometry will be more repeatible (and hence more reliable). The modification is subtle, yet complex to carry out robustly. See Improved Ellipse Fitting and Isophotal Photometry in Crowded Fields for a description of the algorithm.

The following examples show the resultant stellar subtraction around galaxies using the new algorithm. The images come from the extracted postage stamp images, where a new modification is to add three new planes showing the field with stars subtracted.

Note that stars nicely subtract from the images. Very bright stars subtract reasonably well, with some residual left over. Neighboring galaxy subtraction is not as good due to the design: the objects are *assumed* to be point sources that follow the PSF (or generalized exp function). Subtraction is usually very good for stars well separated from the nuclear regions. Nuclear contamination (star within a few pixels of the nucleus) represents the most destructive contamination and for which our correction is shakey -- fortunately these cases are rare. Finally, note that for the larger galaxies, there are in some cases 'false' sources that are being subtracted (this is due to the fact that the PIXPHOT star detector is finding chaff within galaxies, resulting in unwanted chaos).

Examples of Sources in the Galactic Plane (glon = 40, glat = 0) Notes: Stellar contamination is brutal for these examples (sources density > 4.1). The method is failing for close nuclear contamination. Some adjustment is needed to minimize destruction of the nucleus.

Examples of Large Galaxies with star subtraction
(warning: these images are BIG!) Notes: The second image represents the star-subtracted image. Since the maximum working area is 120" in radius, the image itself may be larger than the working area. Hence, I have masked away any parts of the image that were not under the star-subtraction jurisdiction. Note also that the subtraction is carried out assuming a point-source profile -- that is, we assume the sources are stars. That is why the subtraction is lousy for actual galaxies (see for example, Group).

Discussion: Overall the star subtraction about large galaxies is working fine. But there are some obvious problems: pieces of big galaxies are chopped to bits by nearby star (and galaxy) subtraction/masking. These "sources" are clearly not being characterized correctly (and there is probably no way to do it right in any case). The second obvious problem is that too many "stars" are being subtracted -- that is, pieces of the galaxy itself. How do we avoid subtracting H II regions and noise bumps on top of big galaxies? One idea: use the PSF-fit CHI^2 to eliminate these sources (which presumably have a large CHI^2) from the subtraction list. When do we apply this criterion? Only with big galaxies? Uniformly throughout the survey? Not at all? In any event, extended sources around bright galaxies should probably be treated as chaff and filtered accordingly from catalogs.

Note: I made some improvements that greatly reduced the number of sources subtracted from large galaxies. Improvs include: apply PSFCHI and local-max criteria for coadds with galaxies > 4', and subtraction of only stars with mags within 2.5 mag of the primary (thus for big bright galaxies, we leave alone the faint stars).

Examples of Galaxies in Abell 3627 (Great Attractor), glon = 320, glat = -5 Notes: The images were generated using the latest version of GALWORKS (V3) that incorporates the new method for star subtraction.

Updated Oblique Decision Trees

The training sets used for the OBDT classifier have tripled in number since the last time I build the trees. It is high time to revisit the classification scheme. New trees will be constructed using training sets with some 160K sources. A new method for combining the parameter space and subsquently derived trees will be carried out and compared with current (V2) OBDT-derived Gscore.

Nominal Results, using the GALWORKS V.2 classifier.
Gscore limit = 1.4.

Abell 3558 Repeat Scans: 2.0 < Density < 3.6
Jlow Jhigh nGT nG C nB R nS nD nT
9.00 12.00 17 17 1.00 0 1.00 0 0 0
12.00 13.00 398 377 0.95 0 1.00 0 0 0
13.00 14.00 1371 1328 0.97 1 1.00 0 1 0
14.00 14.50 1775 1678 0.95 1 1.00 0 1 0
14.50 14.75 937 798 0.85 7 0.99 4 1 2
14.75 15.00 993 824 0.83 20 0.98 9 9 2
15.00 15.50 4311 3388 0.79 321 0.91 237 74 10
---- ---- 9802 8410 ---- 350 ---- ---- ---- ----
Hlow Hhigh nGT nG C nB R nS nD nT
8.50 11.50 14 14 1.00 0 1.00 0 0 0
11.50 12.50 303 303 1.00 0 1.00 0 0 0
12.50 13.50 1954 1890 0.97 1 1.00 1 0 0
13.50 14.00 1734 1582 0.91 8 0.99 5 2 1
14.00 14.25 1010 851 0.84 16 0.98 12 3 1
14.25 14.50 1229 979 0.80 30 0.97 21 5 4
14.50 15.00 3540 2775 0.78 294 0.90 210 76 8
---- ---- 9802 8410 ---- 350 ---- ---- ---- ----
Klow Khigh nGT nG C nB R nS nD nT
8.00 11.00 20 20 1.00 0 1.00 0 0 0
11.00 12.00 442 419 0.95 0 1.00 0 0 0
12.00 13.00 1551 1525 0.98 1 1.00 0 1 0
13.00 13.50 1842 1746 0.95 3 1.00 2 1 0
13.50 13.75 1009 939 0.93 16 0.98 12 3 1
13.75 14.00 1428 1257 0.88 41 0.97 28 11 2
14.00 14.50 3477 2475 0.71 288 0.90 207 70 11
---- ---- 9802 8410 ---- 350 ---- ---- ---- ----

Big Galaxies (M31, M32, M33, M51, M66, M101, Maffei 2) fields
Jlow Jhigh nGT nG C nB R nS nD nT
9.00 12.00 9 9 1.00 5 0.64 5 0 0
12.00 13.00 10 10 1.00 8 0.56 5 2 1
13.00 14.00 51 51 1.00 17 0.75 11 4 2
14.00 14.50 86 84 0.98 23 0.79 18 2 3
14.50 14.75 89 82 0.92 8 0.91 3 4 1
14.75 15.00 95 91 0.96 9 0.91 6 2 1
15.00 15.50 472 440 0.93 70 0.86 48 21 1
---- ---- 812 767 ---- 140 ---- ---- ---- ----
Hlow Hhigh nGT nG C nB R nS nD nT
8.50 11.50 12 12 1.00 6 0.67 6 0 0
11.50 12.50 9 9 1.00 7 0.56 6 1 0
12.50 13.50 82 80 0.98 32 0.71 25 6 1
13.50 14.00 140 134 0.96 24 0.85 15 5 4
14.00 14.25 102 97 0.95 10 0.91 10 0 0
14.25 14.50 108 100 0.93 11 0.90 3 7 1
14.50 15.00 357 333 0.93 50 0.87 31 16 3
---- ---- 812 767 ---- 140 ---- ---- ---- ----
Klow Khigh nGT nG C nB R nS nD nT
8.00 11.00 9 9 1.00 4 0.69 4 0 0
11.00 12.00 11 11 1.00 8 0.58 6 1 1
12.00 13.00 69 67 0.97 24 0.74 15 6 3
13.00 13.50 135 130 0.96 18 0.88 11 4 3
13.50 13.75 110 108 0.98 16 0.87 13 3 0
13.75 14.00 153 147 0.96 18 0.89 11 6 1
14.00 14.50 323 293 0.91 51 0.85 35 15 1
---- ---- 812 767 ---- 140 ---- ---- ---- ----
Great Attractor+ Scans: 3.5 < Density < 4.0
Jlow Jhigh nGT nG C nB R nS nD nT
9.00 12.00 3 3 1.00 0 1.00 0 0 0
12.00 13.00 13 13 1.00 0 1.00 0 0 0
13.00 14.00 36 34 0.94 1 0.97 0 1 0
14.00 14.50 45 42 0.93 1 0.98 1 0 0
14.50 14.75 24 19 0.79 2 0.90 1 0 1
14.75 15.00 16 11 0.69 2 0.85 0 0 2
15.00 15.50 17 10 0.59 3 0.77 0 2 1
---- ---- 154 132 ---- 9 ---- ---- ---- ----
Hlow Hhigh nGT nG C nB R nS nD nT
8.50 11.50 5 5 1.00 0 1.00 0 0 0
11.50 12.50 14 14 1.00 0 1.00 0 0 0
12.50 13.50 47 46 0.98 0 1.00 0 0 0
13.50 14.00 53 45 0.85 3 0.94 2 0 1
14.00 14.25 13 8 0.62 1 0.89 0 0 1
14.25 14.50 6 3 0.50 1 0.75 0 0 1
14.50 15.00 16 11 0.69 4 0.73 0 3 1
---- ---- 154 132 ---- 9 ---- ---- ---- ----
Klow Khigh nGT nG C nB R nS nD nT
8.00 11.00 4 4 1.00 0 1.00 0 0 0
11.00 12.00 16 16 1.00 0 1.00 0 0 0
12.00 13.00 50 47 0.94 1 0.98 0 1 0
13.00 13.50 56 51 0.91 2 0.96 1 0 1
13.50 13.75 19 10 0.53 1 0.91 1 0 0
13.75 14.00 6 3 0.50 2 0.60 0 0 2
14.00 14.50 2 0 0.00 3 0.00 0 2 1
---- ---- 154 132 ---- 9 ---- ---- ---- ----

Great Attractor+ Scans: 4.0 < Density < 5.0
Jlow Jhigh nGT nG C nB R nS nD nT
9.00 12.00 15 15 1.00 0 1.00 0 0 0
12.00 13.00 34 33 0.97 0 1.00 0 0 0
13.00 14.00 26 26 1.00 0 1.00 0 0 0
14.00 14.50 14 12 0.86 0 1.00 0 0 0
14.50 14.75 2 2 1.00 0 1.00 0 0 0
14.75 15.00 1 0 0.00 0 0.00 0 0 0
15.00 15.50 0 0 0.00 1 0.00 0 0 1
---- ---- 92 88 ---- 1 ---- ---- ---- ----
Hlow Hhigh nGT nG C nB R nS nD nT
8.50 11.50 21 21 1.00 0 1.00 0 0 0
11.50 12.50 21 20 0.95 0 1.00 0 0 0
12.50 13.50 21 21 1.00 1 0.95 0 0 1
13.50 14.00 8 6 0.75 0 1.00 0 0 0
14.00 14.25 1 0 0.00 0 0.00 0 0 0
14.25 14.50 0 0 0.00 0 0.00 0 0 0
14.50 15.00 20 20 1.00 0 1.00 0 0 0
---- ---- 92 88 ---- 1 ---- ---- ---- ----
Klow Khigh nGT nG C nB R nS nD nT
8.00 11.00 18 18 1.00 0 1.00 0 0 0
11.00 12.00 31 30 0.97 0 1.00 0 0 0
12.00 13.00 30 30 1.00 0 1.00 0 0 0
13.00 13.50 11 9 0.82 1 0.90 0 0 1
13.50 13.75 2 1 0.50 0 1.00 0 0 0
13.75 14.00 0 0 0.00 0 0.00 0 0 0
14.00 14.50 0 0 0.00 0 0.00 0 0 0
---- ---- 92 88 ---- 1 ---- ---- ---- ----


Re-building the OBDT

The first order of business is to determine the "normalization" factors per star-galaxy discriment. The normalization factor corresponds to the "lower quartile" of the score distribution (vs. mag).
Mag ranges: 12.5-13.5 (J), 12-13 (H),11.5-12.5 (K)

Low Density

Moderate Density (<3.6) High Density (~4.0) Notice that the MXDN score drops significantly with density (i.e., the surface brightness of the source is getting larger), while the Color score is increasing with density (i.e., interstellar reddening).

Normalization vs. Density

Results of Normalization

Thoughts
The star-galaxy discrimination scores are robust for nearly all stellar densities, the exception being "super" high density, > 4.4. Consider each density range separately, starting with the most difficult set, the "super high density fields":

Results

New OBDT , with Impurity Measure == Twoing Rule

New OBDT , with Impurity Measure == Gini Index

New OBDT , with Impurity Measure == Variance

New OBDT , with Impurity Measure == Twoing Rule

Test 9: GALWORKS w/OBDT Installed (old version)
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2397_2393 2608_2655 0.920_0.900 817_811 1035_1091 0.789_0.743
H7_comp_1.tbl 13.70 14.20 1176_1135 1374_1383 0.860_0.820 458_423 609_588 0.752_0.719
K7_comp_1.tbl 13.00 13.50 1427_1395 1423_1393 1.000_1.000 240_254 297_335 0.808_0.758
J7_comp_2.tbl 14.00 15.00 13_12 187_159 0.070_0.080 14_13 188_173 0.074_0.075
H7_comp_2.tbl 13.70 14.20 14_13 182_156 0.080_0.080 4_4 75_76 0.053_0.053
K7_comp_2.tbl 13.00 13.50 0_0 0_0 0.000_0.000 5_5 50_51 0.100_0.098
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 107_102 14.430_14.420 0.066_0.065 35_33 14.550_14.530 0.098_0.077
H7_repeats_1.tbl 13.70 14.20 49_42 13.950_13.930 0.107_0.103 17_16 13.980_13.990 0.118_0.121
K7_repeats_1.tbl 13.00 13.50 74_72 13.230_13.230 0.095_0.094 11_11 13.250_13.210 0.100_0.090
Jf20e_repeats_1.tbl 14.00 15.00 100_95 14.450_14.430 0.078_0.076 37_36 14.530_14.520 0.094_0.093
Hf20e_repeats_1.tbl 13.70 14.20 43_38 13.930_13.920 0.103_0.100 18_16 14.000_14.000 0.122_0.117
Kf20e_repeats_1.tbl 13.00 13.50 66_65 13.250_13.250 0.122_0.121 14_14 13.200_13.170 0.127_0.118
Jf20c_repeats_1.tbl 14.00 15.00 101_95 14.430_14.410 0.072_0.072 37_37 14.530_14.510 0.085_0.082
Hf20c_repeats_1.tbl 13.70 14.20 46_39 13.950_13.930 0.110_0.107 21_18 13.990_13.990 0.119_0.114
Kf20c_repeats_1.tbl 13.00 13.50 69_67 13.230_13.230 0.113_0.113 14_14 13.220_13.190 0.119_0.109
RKf0e_repeats_1.tbl 10.00 20.00 39_40 12.130_12.180 1.350_1.470 31_30 13.380_13.330 1.810_1.657
RKf0c_repeats_1.tbl 10.00 20.00 16_16 11.960_11.960 1.145_1.145 23_22 13.290_13.370 1.213_1.185
J_ba_repeats_1.tbl 0.20 0.80 21_21 0.520_0.520 0.063_0.064 87_84 0.550_0.540 0.085_0.076
K_ba_repeats_1.tbl 0.20 0.80 21_21 0.520_0.520 0.069_0.070 93_90 0.560_0.560 0.091_0.086
S_ba_repeats_1.tbl 0.20 0.80 19_19 0.500_0.500 0.071_0.071 89_86 0.550_0.550 0.079_0.068
J20e_Jext_repeats_1.0.01 0.80 123_115 0.320_0.320 0.112_0.111 81_76 0.370_0.370 0.115_0.113
H20e_Hext_repeats_1.0.01 0.80 99_94 0.320_0.310 0.122_0.119 62_60 0.340_0.340 0.114_0.115
K20e_Kext_repeats_1.0.01 0.80 71_66 0.290_0.290 0.118_0.118 40_39 0.280_0.280 0.097_0.096

Test 10: New Gscore(variance) vs. Old Gscore
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2367_2397 2514_2608 0.940_0.920 884_817 1100_1035 0.804_0.789
H7_comp_1.tbl 13.70 14.20 1144_1176 1327_1374 0.860_0.860 485_458 659_609 0.736_0.752
K7_comp_1.tbl 13.00 13.50 1378_1427 1367_1423 1.010_1.000 264_240 335_297 0.788_0.808
J7_comp_2.tbl 14.00 15.00 10_13 146_187 0.070_0.070 9_14 109_188 0.083_0.074
H7_comp_2.tbl 13.70 14.20 9_14 125_182 0.070_0.080 1_4 11_75 0.091_0.053
K7_comp_2.tbl 13.00 13.50 1_0 13_0 0.080_0.000 3_5 17_50 0.176_0.100
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 109_107 14.440_14.430 0.068_0.066 36_35 14.580_14.550 0.114_0.098
H7_repeats_1.tbl 13.70 14.20 48_49 13.940_13.950 0.104_0.107 19_17 14.020_13.980 0.124_0.118
K7_repeats_1.tbl 13.00 13.50 70_74 13.230_13.230 0.092_0.095 12_11 13.240_13.250 0.092_0.100
Jf20e_repeats_1.tbl 14.00 15.00 102_100 14.470_14.450 0.082_0.078 38_37 14.550_14.530 0.096_0.094
Hf20e_repeats_1.tbl 13.70 14.20 46_43 13.940_13.930 0.100_0.103 17_18 14.030_14.000 0.125_0.122
Kf20e_repeats_1.tbl 13.00 13.50 64_66 13.240_13.250 0.120_0.122 15_14 13.180_13.200 0.131_0.127
Jf20c_repeats_1.tbl 14.00 15.00 103_101 14.430_14.430 0.075_0.072 38_37 14.560_14.530 0.092_0.085
Hf20c_repeats_1.tbl 13.70 14.20 46_46 13.940_13.950 0.111_0.110 20_21 14.010_13.990 0.121_0.119
Kf20c_repeats_1.tbl 13.00 13.50 67_69 13.230_13.230 0.111_0.113 14_14 13.220_13.220 0.120_0.119
RKf0e_repeats_1.tbl 10.00 20.00 39_39 12.140_12.130 1.366_1.350 30_31 13.370_13.380 1.664_1.810
RKf0c_repeats_1.tbl 10.00 20.00 16_16 11.960_11.960 1.145_1.145 23_23 13.290_13.290 1.214_1.213
J_ba_repeats_1.tbl 0.20 0.80 21_21 0.520_0.520 0.067_0.063 85_87 0.550_0.550 0.082_0.085
K_ba_repeats_1.tbl 0.20 0.80 21_21 0.510_0.520 0.068_0.069 91_93 0.560_0.560 0.088_0.091
S_ba_repeats_1.tbl 0.20 0.80 19_19 0.510_0.500 0.073_0.071 86_89 0.550_0.550 0.075_0.079
J20e_Jext_repeats_1.0.01 0.80 123_123 0.330_0.320 0.115_0.112 77_81 0.370_0.370 0.113_0.115
H20e_Hext_repeats_1.0.01 0.80 97_99 0.310_0.320 0.117_0.122 60_62 0.340_0.340 0.115_0.114
K20e_Kext_repeats_1.0.01 0.80 69_71 0.300_0.290 0.123_0.118 36_40 0.280_0.280 0.096_0.097

Test 11: New Gscore(twoing) vs. New Gscore(variance)
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2355_2367 2510_2514 0.940_0.940 890_884 1080_1100 0.824_0.804
H7_comp_1.tbl 13.70 14.20 1161_1144 1339_1327 0.870_0.860 490_485 652_659 0.752_0.736
K7_comp_1.tbl 13.00 13.50 1343_1378 1342_1367 1.000_1.010 255_264 319_335 0.799_0.788
J7_comp_2.tbl 14.00 15.00 12_10 179_146 0.070_0.070 8_9 97_109 0.082_0.083
H7_comp_2.tbl 13.70 14.20 8_9 112_125 0.070_0.070 1_1 11_11 0.091_0.091
K7_comp_2.tbl 13.00 13.50 2_1 41_13 0.050_0.080 3_3 17_17 0.176_0.176
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 103_109 14.440_14.440 0.067_0.068 34_36 14.620_14.580 0.118_0.114
H7_repeats_1.tbl 13.70 14.20 49_48 13.950_13.940 0.103_0.104 19_19 14.010_14.020 0.125_0.124
K7_repeats_1.tbl 13.00 13.50 65_70 13.230_13.230 0.093_0.092 10_12 13.260_13.240 0.092_0.092
Jf20e_repeats_1.tbl 14.00 15.00 95_102 14.460_14.470 0.079_0.082 36_38 14.580_14.550 0.102_0.096
Hf20e_repeats_1.tbl 13.70 14.20 45_46 13.930_13.940 0.099_0.100 17_17 14.030_14.030 0.126_0.125
Kf20e_repeats_1.tbl 13.00 13.50 60_64 13.250_13.240 0.121_0.120 12_15 13.190_13.180 0.141_0.131
Jf20c_repeats_1.tbl 14.00 15.00 96_103 14.430_14.430 0.073_0.075 37_38 14.600_14.560 0.097_0.092
Hf20c_repeats_1.tbl 13.70 14.20 46_46 13.950_13.940 0.107_0.111 21_20 14.020_14.010 0.123_0.121
Kf20c_repeats_1.tbl 13.00 13.50 62_67 13.230_13.230 0.112_0.111 11_14 13.250_13.220 0.130_0.120
RKf0e_repeats_1.tbl 10.00 20.00 39_39 12.130_12.140 1.360_1.366 30_30 13.370_13.370 1.664_1.664
RKf0c_repeats_1.tbl 10.00 20.00 16_16 11.960_11.960 1.145_1.145 23_23 13.290_13.290 1.214_1.214
J_ba_repeats_1.tbl 0.20 0.80 21_21 0.520_0.520 0.067_0.067 86_85 0.550_0.550 0.082_0.082
K_ba_repeats_1.tbl 0.20 0.80 21_21 0.510_0.510 0.068_0.068 92_91 0.560_0.560 0.088_0.088
S_ba_repeats_1.tbl 0.20 0.80 19_19 0.510_0.510 0.073_0.073 87_86 0.550_0.550 0.075_0.075
J20e_Jext_repeats_1.0.01 0.80 118_123 0.330_0.330 0.115_0.115 74_77 0.380_0.370 0.117_0.113
H20e_Hext_repeats_1.0.01 0.80 93_97 0.310_0.310 0.117_0.117 59_60 0.350_0.340 0.115_0.115
K20e_Kext_repeats_1.0.01 0.80 67_69 0.290_0.300 0.117_0.123 36_36 0.280_0.280 0.096_0.096

Effective "half-light" Radius & Surface Brightness

The half-light radius springs from the "total" flux measurement. The total flux corresponds to the isophotal + extrapolated combination. The extrapolation refers to the exponential fit (alpha,beta,f0) to the radial profile, extrapolated to radii beyond the isophotal (~1-sigma) radius.

Algorithm: Fit the radial profile using the modified exponential function (F0, alpha & beta). Here we avoid the core: radius > 5". We avoid low SNR pixels by applying an SNR threshold = 1.5 (where sigma corresponds to the uncertainty in the median isophotal value: sigma = RMS / sqrt(n/4) , where RMS is the rms uncertainty in the pixel population (within isophote annulus), n is hte number of pixels in the annulus and the factor 4 takes into account the correlated pixels. The quality of the fit, Pchi (reduced chi^2), is now part of the GALWORKS output. If Pchi is greater than 2.0, the fit is poor and no extrapolation is attempted . Most fits have Pchi values much smaller than unity. The parameters of the fit (F0, alpha & beta) are then used to extrapolate beyond the 20 mag/arcsec^2 isophote. The function is extrapolated from the isophotal radius (20 mag/arcsec^2) out to a maximum given by 10 * (1 / alpha), that is, the scale length of the disk.

The half-light flux corresponds to half of the total (or isophotal + extrapolated) flux. I then integrate starting from a radius of zero, with small increments, until the half-light flux is achieved. This is at the half-light radius. The flux is then normalized by the total number of pixels in the half-light radial aperture and a surface brightness is output.

I use elliptical apertures for the fit, extrapolation and half-light determination.

Photometry
RJext Jext RHext Hext RKext Kext
29.6 13.321 31.6 12.199 21.6 12.201
RJf0e J0fe RHf0e H0fe RKf0e K0fe
11.0 13.547 11.0 12.598 11.0 12.314
RJeff Jeff RHeff Heff RKeff Keff
5.30 18.10 6.40 17.38 4.49 16.61

Photometry
RJext Jext RHext Hext RKext Kext
65.9 9.848 63.2 9.164 64.7 8.892
RJf0e J0fe RHf0e H0fe RKf0e K0fe
39.0 9.942 39.0 9.271 39.0 9.009
RJeff Jeff RHeff Heff RKeff Keff
13.69 17.36 13.62 16.67 13.74 16.41

Photometry
RJext Jext RHext Hext RKext Kext
34.4 13.405 24.3 12.769 25.1 12.449
RJf0e J0fe RHf0e H0fe RKf0e K0fe
8.8 13.720 8.8 12.981 8.8 12.654
RJeff Jeff RHeff Heff RKeff Keff
4.83 18.40 4.14 17.44 4.13 17.09

Test 13: vs. Test 10
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2317_2367 2513_2514 0.920_0.940 869_884 1119_1100 0.777_0.804
H7_comp_1.tbl 13.70 14.20 1118_1144 1326_1327 0.840_0.860 457_485 553_659 0.826_0.736
K7_comp_1.tbl 13.00 13.50 1375_1378 1396_1367 0.980_1.010 239_264 305_335 0.784_0.788
J7_comp_2.tbl 14.00 15.00 9_10 138_146 0.070_0.070 8_9 93_109 0.086_0.083
H7_comp_2.tbl 13.70 14.20 10_9 139_125 0.070_0.070 1_1 11_11 0.091_0.091
K7_comp_2.tbl 13.00 13.50 1_1 14_13 0.070_0.080 2_3 17_17 0.118_0.176
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 103_109 14.430_14.440 0.067_0.068 31_36 14.580_14.580 0.098_0.114
H7_repeats_1.tbl 13.70 14.20 44_48 13.950_13.940 0.104_0.104 16_19 14.030_14.020 0.115_0.124
K7_repeats_1.tbl 13.00 13.50 69_70 13.220_13.230 0.093_0.092 9_12 13.240_13.240 0.089_0.092
Jf20e_repeats_1.tbl 14.00 15.00 97_102 14.460_14.470 0.076_0.082 30_38 14.580_14.550 0.090_0.096
Hf20e_repeats_1.tbl 13.70 14.20 46_46 13.940_13.940 0.098_0.100 12_17 13.990_14.030 0.102_0.125
Kf20e_repeats_1.tbl 13.00 13.50 62_64 13.240_13.240 0.114_0.120 11_15 13.210_13.180 0.093_0.131
Jf20c_repeats_1.tbl 14.00 15.00 100_103 14.430_14.430 0.071_0.075 30_38 14.580_14.560 0.084_0.092
Hf20c_repeats_1.tbl 13.70 14.20 44_46 13.940_13.940 0.104_0.111 16_20 14.030_14.010 0.117_0.121
Kf20c_repeats_1.tbl 13.00 13.50 67_67 13.230_13.230 0.102_0.111 10_14 13.220_13.220 0.090_0.120
J_ba_repeats_1.tbl 0.20 0.80 31_39 0.560_12.140 0.078_1.366 86_30 0.560_13.370 0.079_1.664
K_ba_repeats_1.tbl 0.20 0.80 31_16 0.550_11.960 0.078_1.145 95_23 0.580_13.290 0.086_1.214
S_ba_repeats_1.tbl 0.20 0.80 26_21 0.520_0.520 0.073_0.067 88_85 0.560_0.550 0.078_0.082
J20e_Jext_repeats_1.0.01 0.80 170_21 0.220_0.510 0.126_0.068 86_91 0.230_0.560 0.145_0.088
H20e_Hext_repeats_1.0.01 0.80 179_19 0.220_0.510 0.173_0.073 87_86 0.210_0.550 0.168_0.075
K20e_Kext_repeats_1.0.01 0.80 182_123 0.180_0.330 0.172_0.115 86_77 0.180_0.370 0.131_0.113

Bright Star Processing/Masking

See Bright Star Masking for method and calibration (e.g., parameter tuning).

Test 19 , improved Kron photometry Test 19: vs. Test 18, Improved Kron mag
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2470_2438 2593_2561 0.950_0.950 816_823 1009_1110 0.809_0.741
H7_comp_1.tbl 13.70 14.20 1182_1152 1328_1329 0.890_0.870 411_449 543_585 0.757_0.768
K7_comp_1.tbl 13.00 13.50 1385_1377 1359_1359 1.020_1.010 203_215 277_291 0.733_0.739
J7_comp_2.tbl 14.00 15.00 19_19 219_219 0.090_0.090 16_16 184_184 0.087_0.087
H7_comp_2.tbl 13.70 14.20 12_12 167_167 0.070_0.070 1_1 11_11 0.091_0.091
K7_comp_2.tbl 13.00 13.50 5_5 13_13 0.380_0.380 2_2 17_17 0.118_0.118
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 117_114 14.450_14.450 0.068_0.068 33_32 14.560_14.600 0.117_0.096
H7_repeats_1.tbl 13.70 14.20 53_51 13.950_13.950 0.104_0.104 16_16 14.030_14.030 0.115_0.115
K7_repeats_1.tbl 13.00 13.50 74_73 13.230_13.230 0.092_0.092 9_8 13.240_13.250 0.095_0.094
Jf20e_repeats_1.tbl 14.00 15.00 111_109 14.480_14.480 0.079_0.079 31_29 14.570_14.590 0.095_0.094
Hf20e_repeats_1.tbl 13.70 14.20 53_52 13.940_13.940 0.099_0.099 13_12 14.000_14.000 0.108_0.107
Kf20e_repeats_1.tbl 13.00 13.50 69_68 13.240_13.240 0.112_0.112 10_9 13.210_13.220 0.102_0.097
Jf20c_repeats_1.tbl 14.00 15.00 113_111 14.450_14.450 0.072_0.072 33_32 14.580_14.610 0.092_0.096
Hf20c_repeats_1.tbl 13.70 14.20 53_52 13.950_13.950 0.107_0.107 17_16 14.020_14.020 0.116_0.116
Kf20c_repeats_1.tbl 13.00 13.50 71_70 13.230_13.230 0.100_0.101 10_9 13.200_13.220 0.098_0.093
RKf0e_repeats_1.tbl 10.00 20.00 29_29 12.680_12.680 1.294_1.294 26_27 14.020_13.920 1.553_1.683
RKf0c_repeats_1.tbl 10.00 20.00 10_10 12.310_12.310 1.073_1.073 15_14 13.240_13.470 1.210_1.242
J_ba_repeats_1.tbl 0.20 0.80 53_29 0.610_0.560 0.090_0.077 138_86 0.590_0.560 0.093_0.078
K_ba_repeats_1.tbl 0.20 0.80 57_31 0.620_0.570 0.092_0.075 147_94 0.610_0.580 0.103_0.088
S_ba_repeats_1.tbl 0.20 0.80 44_25 0.580_0.520 0.088_0.070 135_86 0.590_0.560 0.095_0.077
J20e_Jext_repeats_1.0.01 0.80 189_191 0.170_0.170 0.091_0.090 90_87 0.210_0.210 0.087_0.087
H20e_Hext_repeats_1.0.01 0.80 199_196 0.150_0.150 0.110_0.106 87_85 0.190_0.180 0.108_0.102
K20e_Kext_repeats_1.0.01 0.80 156_166 0.120_0.120 0.105_0.102 67_64 0.180_0.180 0.093_0.094
RkronE_repeats_1.tbl10.00 20.00 0_0 0.000_0.000 0.000_0.000 0_0 0.000_0.000 0.000_0.000
JkronE_repeats_1.tbl14.00 15.00 82_95 14.430_14.410 0.109_0.092 59_45 14.500_14.560 0.135_0.129
JkronE_repeats_1.tbl13.70 14.20 38_40 13.990_14.000 0.086_0.076 27_20 13.970_14.010 0.098_0.084
JkronE_repeats_1.tbl13.00 13.50 12_16 13.240_13.230 0.062_0.060 21_17 13.260_13.260 0.095_0.107
RkronC_repeats_1.tbl10.00 20.00 54_20 12.120_12.380 1.966_2.510 81_43 12.550_12.980 2.115_2.960
JkronC_repeats_1.tbl14.00 15.00 81_98 14.420_14.410 0.106_0.095 58_45 14.500_14.540 0.131_0.121
JkronC_repeats_1.tbl13.70 14.20 39_38 13.990_14.000 0.081_0.074 27_22 13.980_14.010 0.097_0.090
JkronC_repeats_1.tbl13.00 13.50 15_16 13.220_13.260 0.063_0.068 20_18 13.260_13.250 0.080_0.097
J20e_Jkron_repeats_10.01 0.50 183_178 0.130_0.080 0.079_0.057 89_84 0.170_0.120 0.081_0.078
H20e_Hkron_repeats_10.01 0.50 191_188 0.130_0.080 0.092_0.065 86_82 0.160_0.120 0.090_0.080
K20e_Kkron_repeats_10.01 0.50 202_200 0.140_0.090 0.117_0.083 87_81 0.170_0.120 0.109_0.096
Test 20 , improved star subtraction for spirals Test 20: vs. Test 18, Improved Star Subtraction
-- -- -- non-contaminated ... | contaminated ... |
fname mag- mag+ #r #p C #r #p C
J7_comp_1.tbl 14.00 15.00 2518_2438 2715_2561 0.930_0.950 827_823 998_1110 0.829_0.741
H7_comp_1.tbl 13.70 14.20 1194_1152 1406_1329 0.850_0.870 431_449 489_585 0.881_0.768
K7_comp_1.tbl 13.00 13.50 1416_1377 1416_1359 1.000_1.010 222_215 258_291 0.860_0.739
J7_comp_2.tbl 14.00 15.00 21_19 257_219 0.080_0.090 20_16 231_184 0.087_0.087
H7_comp_2.tbl 13.70 14.20 11_12 153_167 0.070_0.070 1_1 11_11 0.091_0.091
K7_comp_2.tbl 13.00 13.50 5_5 13_13 0.380_0.380 2_2 17_17 0.118_0.118
fname val- val+ # valbar RMS # valbar RMS
J7_repeats_1.tbl 14.00 15.00 118_114 14.450_14.450 0.068_0.068 36_32 14.580_14.600 0.096_0.096
H7_repeats_1.tbl 13.70 14.20 53_51 13.950_13.950 0.104_0.104 18_16 14.030_14.030 0.136_0.115
K7_repeats_1.tbl 13.00 13.50 75_73 13.230_13.230 0.092_0.092 11_8 13.240_13.250 0.098_0.094
Jf20e_repeats_1.tbl 14.00 15.00 110_109 14.480_14.480 0.078_0.079 35_29 14.550_14.590 0.103_0.094
Hf20e_repeats_1.tbl 13.70 14.20 52_52 13.940_13.940 0.099_0.099 14_12 14.010_14.000 0.108_0.107
Kf20e_repeats_1.tbl 13.00 13.50 70_68 13.240_13.240 0.111_0.112 12_9 13.200_13.220 0.130_0.097
Jf20c_repeats_1.tbl 14.00 15.00 113_111 14.440_14.450 0.072_0.072 38_32 14.600_14.610 0.104_0.096
Hf20c_repeats_1.tbl 13.70 14.20 52_52 13.950_13.950 0.107_0.107 19_16 14.030_14.020 0.120_0.116
Kf20c_repeats_1.tbl 13.00 13.50 72_70 13.230_13.230 0.102_0.101 13_9 13.220_13.220 0.110_0.093
RKf0e_repeats_1.tbl 10.00 20.00 31_29 13.000_12.680 1.308_1.294 25_27 13.550_13.920 1.571_1.683
RKf0c_repeats_1.tbl 10.00 20.00 12_10 12.250_12.310 1.111_1.073 17_14 13.080_13.470 1.384_1.242
J_ba_repeats_1.tbl 0.20 0.80 35_29 0.590_0.560 0.073_0.077 105_86 0.570_0.560 0.074_0.078
K_ba_repeats_1.tbl 0.20 0.80 37_31 0.600_0.570 0.072_0.075 111_94 0.590_0.580 0.082_0.088
S_ba_repeats_1.tbl 0.20 0.80 30_25 0.550_0.520 0.071_0.070 107_86 0.570_0.560 0.079_0.077
J20e_Jext_repeats_1.0.01 0.80 197_191 0.170_0.170 0.083_0.090 92_87 0.200_0.210 0.089_0.087
H20e_Hext_repeats_1.0.01 0.80 207_196 0.170_0.150 0.100_0.106 88_85 0.190_0.180 0.102_0.102
K20e_Kext_repeats_1.0.01 0.80 214_166 0.150_0.120 0.079_0.102 88_64 0.170_0.180 0.081_0.094
RkronE_repeats_1.tbl10.00 20.00 85_0 12.560_0.000 1.909_0.000 73_0 13.210_0.000 2.298_0.000
JkronE_repeats_1.tbl13.70 14.20 43_95 14.010_14.410 0.073_0.092 25_45 14.010_14.560 0.107_0.129
JkronE_repeats_1.tbl13.00 13.50 17_40 13.240_14.000 0.047_0.076 16_20 13.260_14.010 0.074_0.084
RkronC_repeats_1.tbl10.00 20.00 26_16 12.440_13.230 1.611_0.060 44_17 12.790_13.260 1.896_0.107
JkronC_repeats_1.tbl14.00 15.00 98_20 14.410_12.380 0.092_2.510 50_43 14.510_12.980 0.119_2.960
JkronC_repeats_1.tbl13.70 14.20 40_98 14.000_14.410 0.071_0.095 22_45 14.010_14.540 0.105_0.121
JkronC_repeats_1.tbl13.00 13.50 19_38 13.260_14.000 0.057_0.074 17_22 13.250_14.010 0.082_0.090
J20e_Jkron_repeats_10.01 0.50 182_16 0.090_13.260 0.046_0.068 89_18 0.120_13.250 0.053_0.097
H20e_Hkron_repeats_10.01 0.50 189_178 0.090_0.080 0.054_0.057 86_84 0.110_0.120 0.052_0.078
K20e_Kkron_repeats_10.01 0.50 184_188 0.090_0.080 0.067_0.065 81_82 0.120_0.120 0.068_0.080