BIBLIOGRAFIA Ley 1607 del 2012.

This chapter provides a more detailed descriptions of the flags used in this catalog. Table 5.7 gives a short description of the fitting parameters used to set the value of each flag. The majority of the flags use the B/T, S´ersic index, and radial light profiles of the galaxy to set the flags. The flags also consider the axis ratio and the difference in position angle of the bulge and disc because small axis ratios combined with large differences in position angle of the two components is an unphysical fit for most cases. B/T(r) in flags 3, 7, 8, etc. refers to the radial B/T profile. For the radial profile, the local B/T ratio (i. e., the ratio of light contributed by the bulge at the annulus of width 1 arcsec centered on radius r to the light contributed by the disc) is plotted. rsextractor is the half-light radius reported by

SExtractorduring fitting. This radius is used to set the scale of the galaxy during fitting

and to test whether components have become unphysically large after fitting.

Flag bit 9 is used to determine whether the bulge and disc are fitting the same component of the galaxy. This is most common in very late-type galaxies (i. e., T-types greater than 4) that have no visible bulge. The flag criteria reference r(0.9Ltot), which is the radius

enclosing 90 per cent of the total light of the galaxy. The flag also measures the quantity

RM S(B/T ₋µ(B/T)) : 0 < r < r(0.9Ltot). The quantity RM S(B/T −µ(B/T)) is the

standard deviation of B/T about the mean B/T value. The average is taken over the radii interior to the radius enclosing 90 per cent of the light. If the standard deviation is less than 0.1, then the B/T ratio is approximately the same at all radii and the components are parallel. Two parallel components, each with S´ersic index <2, are indistinguishable from one brighter exponential component, so these galaxies are flagged as discs and the

5.4 Final Flags

Flag bit Analysis flag Flag criteria

– Good total and component magnitudes and sizes

10 Two-component galaxies

11 No flags No flags are present

12 GoodSer, GoodExp(some flags) Some minor automated flags

13 Flip components Exp component fitting the inner andSercomponent

fitting the outer part of the profile

– Good total magnitudes and sizes only

1 Bulge galaxies

2 NoExpcomponent, nSer>2 1000(B/T-0.8)

3

+(mdisc-19)>0.5 AND nSer≥2

3 Serdominates always B/T(r)≥0.5 for all r AND nSer≥2

4 Disc galaxies

5 NoSercomponent 1000(0.2-B/T)3

+(mbulge-19)>0.5

6 NoExp, nSer<2, Flip Components 1000(B/T-0.8)

3

+(mdisc-19)>0.5 AND nSer<2

7 Serdominates always, nSer<2 B/T(r)≥0.5 for all r AND nSer<2

8 Expdominates always B/T(r)<0.5 for all r

9 Parallel components RM S[(B/T−µ(B/T)) : 0< r < r(0.9Ltot] < 0.1

AND nbulge<2.0

14 Problematic two-component galaxies

15 Serouter only B/T<0.7 AND B/T(r(0.9Ltot)>0.5 AND nbulge≥

2.0 AND B/T(0)>0.5

16 Expinner only B/T(0)<0.5 AND B/T(r: r< 2.7rhl) > 0.5 AND

nbulge≥2.0 AND NOT Ser Outer Only

17 GoodSer, badExp, B/T>=0.5 B/T>0.75 AND ∆φ >45 ANDb/abulge<0.75 AND

b/adisc<0.4

18 BadSer, goodExp, B/T<0.5 B/T<0.25 AND ∆φ >45 ANDb/abulge<0.4 AND

b/adisc<0.75

19 Bulge is point Circularized bulge radius<0.188 arcsec

20 Bad total magnitudes and sizes

21 Centering problems (galaxy centroid-SDSS galaxy centroid)>

0.7×rsextractor

22 Sercomponent contamination by neighbors or sky rbulge,cir/rsextractor>4.0 23 Expcomponent contamination by neighbors or sky rbulge,cir/rsextractor>4.0

24 BadSerand badExpcomponents Failure of measurements

25 Galfitfailure Galfitfails to converge or other failure of the pipeline

26 Polluted or fractured CasJobs neighbors not properly masked/masked or

target is separated into 2 or more objects

Table 5.7: The description of our categories as described in the main text. The major flag

bits used to select different catalogs are flag bits 10 (good two-component fits), 1 (good bulge galaxy), 4 (good disc galaxy), 14 (problematic two-component fit), and 20 (bad fit). The use of these flags is described in Chapter 5.4.

5. FLAGGING AND CLASSIFICATION OF GOOD AND BAD FITS

Flag bit Descriptive Category Per cent SerExp Per cent Test

– Trust total and component

magnitudes and sizes

39.055 39.167

10 Two-component galaxies 39.055 39.167

11 No flags 18.095 17.917

12 GoodSer, goodExp(some flags) 19.417 18.333

13 Flip components 1.543 2.917

– Trust total magnitudes and

sizes only

54.945 54.375

1 Bulge galaxies 18.964 18.958

2 NoExpcomponent, nSer>2 7.074 7.917

3 Serdominates always 11.889 11.042

4 Disc galaxies 25.146 23.958

5 NoSercomponent 16.876 15.625

6 NoExp, nSer<2, flip components 0.551 0.208

7 Serdominates always, nSer<2 0.103 0.625

8 Expdominates always 2.872 2.917

9 Parallel components 4.745 4.583

14 Problematic two-component

galaxies

10.835 11.458

15 Serouter only 7.504 8.125

16 Expinner only 0.425 0.625

17 GoodSer, badExp, B/T>=0.5 0.017 0.000

18 BadSer, goodExp, B/T<0.5 0.652 0.625

26 Bulge is point 2.237 2.083

19 Bad total magnitudes and sizes 6.000 6.458

20 Centering problems 0.557 0.625

21 Ser component contamination by neighbors or sky

2.129 3.333

22 Exp component contamination by neighbors or sky

2.392 2.083

23 BadSerand badExpcomponents 0.239 0.417

24 Galfitfailure 0.355 0.208

25 Polluted or fractured 0.676 0.833

Table 5.8: A breakdown of the descriptive categories useful for analysis. The percentages of

the total catalog are shown for each of the fitted models and our visually classified test set. The one component models (Serand deV) can not be classified as two-component models, by definition. For theSeranddeVmodels, many of the categories are empty. The major distinction for the one-component models is whether the fits have major problems (i. e., flag bit 20 is set).

5.4 Final Flags

components are considered unreliable. The Ser model is the most appropriate model in this case, similar to all the bulge and disc flag categories.

Flag bit 24 (bad Ser and bad Exp) also includes failures that indicate strange fitting behavior. This category includes galaxies where the B/T > 0.5 and the measured B/T is lower than 0.5, or vice versa. These cases occur when the bulge or disc parameters get very unusual (radii approaching 0 or b/a approaching 0).

The remaining flag bits are self-explanatory, so they are not described here. Table 5.8 shows the percentage of galaxies in each flag type for the Ser-Exp model and the visually classified test sample. The percentages for the deV, Ser, deV-Exp, and Ser-Exp models are shown in Table 5.10, 5.11, 5.12, and 5.13, respectively. The one-component models (Serand deV) cannot be classified as two-component models, by definition, so many of the categories are empty. The major distinction for the one-component models is whether the fits have major problems (i. e., flag bit 20 is set). The failure rate (flag bit 20 set) increases with the complexity of the fits, but stays below 7 per cent for the Ser-Exp model and 8 per cent for the test sample. An additional _∼10 per cent of the two-component fits have problematic interpretations. The remaining_∼80₋85 per cent of two-component galaxies appear to have good fits that can be used in analysis. As discussed previously, this does not guarantee that the fits can be interpreted as a physical bulge and a physical disc model. Many caveats to this interpretation still exist.