Previous versions of SEGUE1 Target Selection

Summary of changes from v3.4:

• Low Latitude Algorithms implemented:
  • AGB type objects at low lat
  • K III type objects at low lat
  • Bluetip objects at low lat
  • AMNH high proper motion objects at low lat

Summary of changes from v3.3:

• MSWD colors are now NOT dereddened psf mags (previously were
  dereddened).
• 'l-cut' for Low metallicity backed off to 0.135 from 0.15,
  which allows more in, as too many bright candidates were
  not getting fibers.

Summary of changes from v3.2:

• A/BHB
  • new color cuts (H. Newberg algorithm) g < 20.5, 0.8 < u-g < 1.5, -0.5 < g-r < 0.2, u detection present
  • Also: compute color-gravity index: v = 0.283(u-g) - 0.354(g-r) + 0.455 (r-i) + 0.766 (i-z)
  • Weighting: weight on the 'v' parameter so object with v color of 0 is 4 times as likely to get fiber as v of 0.4.
  • Target count Goal: 150 per plate pair (get ~100 per pair)
• F turnoff
  • s-color cut is no longer present
• Addition of new F/G stars category:
  • bit -2147483136
  • 0.2 < g-r < 0.48, 14.0 < g < 20.2, unbiased random subsampling of this range of g-r color space,
  • Target count Goal: 50 per plate pair
• Low Metallicity
  • New for v3_3: We move the 'l' weight to l-color > 0.15 (was > 0.12). This is more restrictive, hoping to land higher fraction of [Fe/H] < -2 objects.
• Addition of new Main Sequence-White Dwarf pair category (based on color cuts from Potsdam group):
  • Note that for this category only: colors are NOT dereddened.
  • bit -2147479552
    • u-g < 2.25
    • g-r > -0.2
    • g-r < 1.2
    • r-i > 0.5
    • r-i < 2.0
    • g-r > -19.78*(r-i) + 11.13
    • g-r < 0.95*(r-i) + 0.5
    • i-z > 0.5 for r-i > 1.0
    • i-z > 0.68*(r-i)-0.18 for r-i ≤ 1.0
    • 15 < g < 20
  • Target goal: 5 per plate pair, maximum of 10

Summary of changes from v3.1:

• A/BHB selection
  • CHANGE For v3_2: Sort candidates by color, so that all, or most, blue BHBs g-r < 0 , get a fiber.

Summary of changes from v3.0 (in bold):

• Cool White Dwarf:
  • Target goal: 10 per plate pair, but allow overflow if they are present.
• K Giant
  • Target Goal: 95 per plate pair (expected density 4/sq deg = 28/plate pair)
• Low Metallicity
  • New for v 3.1: We also weight by l-color to favor the ones closer to the blue edge of the u-g color in the stellar locus.
• K dwarf
  • Target Goal: 95 per plate pair
• M sub-dwarf
  • M sub-dwarfs (color based West et al.)
    g-r > 1.6, 0.95 < r-i < 1.3, 14.5 < r < 19.0
  • Target count Goal: <~5 per plate pair
  • Selection: magslope 0.9
• Plus: Lepine Shara AMNH high proper motion stars , goal 25-30 per plate pair, proper motion selected.

Summary of changes from v2.0:

• For selections which involve u band, we require that the u flags indicate a u band detection.
• The 'regular SDSS bright end cut' is: No spectra of objects with g, r or i fiber mag < 14.5 allowed.
• For SEGUE v2.0 we cut on r only at r_fiber < 14.5, this resulted in "whopping" fiber warnings for red stars where r-i > 0 → i < 14.5. The spectra were ok however and scattered light was not harmful to adjacent fibers on the CCDs.
• For SEGUE v3_0 we are cutting on i_fiber < 14.2. This allows bright blue things to get spectra and still avoids putting very red bright stars on the plate to scatter.
• Also, proper motions have been included for objects which have matches to the USNO-B catalog and are used in the K giant and Cool White dwarf selection categories.
• Significant changes to Cool White Dwarf, M dwarf
• Addition of Brown dwarf category

Specific category changes (in bold):

• White Dwarf:
  • g < 20.3 , -1 < g-r < -0.2, -1 < u-g < 0.7
  • u-g + 2(g-r) < -0.1
  • Weighting: magslope 1.2
  • Target goal: 25 per plate pair
• Cool White Dwarf:
  • Color cuts:
    • 14.5 < r < 20.5
    • -2 < g-i
    • g-i < 1.7 (if no neighbor with g > 22 within 7 arcsec)
    • otherwise g-i < 0.12
  • Require reliable proper motion (μ) measurement:
    • one-to-one match to USNO_B
    • good proper motion fit (small rems in each coordinate)
    • be detected in all 5 epochs in USNO-B
    • no neighbor brighter than g = 22 within 7 arcsec (to avoid blending problems)
      OR
      blue enough (g-i < 0.12) that target is likely white dwarf
  • Weighting: magslope 1.2
  • Target goal: 10 per plate pair
• A/BHB
  • g < 20.5, 0.6 < u-g < 1.4, -0.5 < g-r < 0.2, s-color < -0.065
  • Weighting: magslope 2.0
  • Target goal: 150 per plate pair (get ~ 100 per pair)
• F turnoff, subdwarf
  • -0.7 < p1(s) < -0.25, 0.4 < u-g < 1.4, 0.2 < g-r < 3.0, g < 20.3
  • Weighting: colorslope + magnitude weighting P1 min/max slope = 5
  • Target goal: 200 per plate pair
• G star
  • 14.0 < r < 20.2, 0.48 < g-r < 0.55
  • Note slightly wider g-r color band to get sufficient targets at high |b|.
  • Weighting: random
  • Target goal: 375 per plate pair
• K Giant
  • r < 20.2, 0.7 < u-g < 4.0 , 0.35 < g-r < 0.8, 0.15 < r-i < 0.6, l-color > 0.07
  • proper_motion < 11 milliarcsec/year and good propermotion match
  • Weighting: magslope 2.0
  • Target Goal: 100 per plate pair
• Low Metallicity
  • 14 < r < 19.5, -0.5 < g-r < 0.75, 0.3 < u-g < 3.0, l-color > 0.12
  • also require detection in u band.
  • Weighting: magslope 1.8 and
  • Faint plate targets sorted by magnitude to 'pack' them, so that brightest ones targeted before fainter ones.
  • Target Goal: 150 per plate pair
• K dwarf
  • 14.5 < r < 19.0, 0.55 < g-r < 0.75
  • Selection: Random subsample
  • Target count Goal: 100 per plate pair
• M sub-dwarf
  • bit -2143289344
  • M sub-dwarfs (color based West et al. )
  • g-r > 1.51, 0.95 < r-i < 1.3, 14.5 < r < 19.0
  • Target count Goal: <~25 per plate pair
  • Selection: magslope 0.9
• L,T brown-dwarf selection
  • bit -2145386496
  • z < 19.5, u > 21, g > 22, r > 21, i-z > 1.7
  • for Brown dwarf selection we require additional flag checks on i and z band as suggested by X. Fan.
  • Target count Goal: < 5 per plate pair
• AGB candidate selection
  • 14.0 < r < 19.0, 2.5 < u-g < 3.5, 0.9 < g-r < 1.3, s-color < -0.06
  • detection in u band required.
  • Selection: magslope 1.4
  • Target count Goal: 10 per plate pair

• All magnitudes are dereddened PSF mags
• Flags: No bright, no edge, no bad interp, no bad deblend
• White dwarf selection
  • bit -2146959360
  • g < 20.3 , -1 < g-r < -0.2, -1 < u-g < 0.5
  • Weighting: colorslope
  • Target count Goal: 25 per plate pair
• Cool White dwarf selection
  • bit -2147352576
  • 15 < r < 20, -0.1 < g-r < 1.1, g-r > 2.4(r-i) + 0.5, i-z < 0
  • Weighting: colorslope
  • Target count Goal: 10 per plate pair
• A/BHB selection
  • bit -2147475456
  • g < 20.5, 0.5 < u-g < 1.4, -0.8 < g-r < 0.2, s-color < -0.065
  • Weighting: colorslope
  • Target count Goal: 150 per plate pair
• F turnoff, sub-dwarf selection
  • bit -2146435072
  • -0.7 < p1(s) < -0.3, 0.4 < u-g < 1.7, -0.3 < g-r < 3, g < 20.3
  • Weighting: colorslope+ magnitude weighting
  • Target count Goal: 150 per plate pair
• G selection
  • bit -2147221504
  • 14.2 < r < 20.2, 0.50 < g-r < 0.55
  • Weighting: random
  • Target count Goal: 375 per plate pair
• K Giant Selection
  • bit -2147467264
  • r < 20.2, 0.7 < u-g < 4.0 , 0.40 < g-r < 1.2, 0.15 < r-i < 0.6, l-color > 0.1
  • proper_motion < 15 arcsec/century (this should have been 1.5 arcsec/cent)
  • Weighting: colorslope
  • Target count Goal: 100 per plate pair
• Low Metallicity selection
  • bit -2147418112
  • r < 20.2, -0.5 < g-r < 0.9, 0.3 < u-g < 3.0, l-color > 0.15
  • Weighting: colorslope
  • Target count Goal: 150 per plate pair
• K dwarf selection
  • bit -2147450880
  • 14.5 < r < 19.5, g-r > 0.7, r-i < 0.8
  • Selection: Random
  • Target count Goal: 125 per plate pair
• M dwarf selection
  • bit -2145386496
  • Three selections in one:
    • regular M dwarfs
    • high velocity M dwarfs (ppm based),
    • M sub-dwarfs (color based)
  • regular M dwarfs: r-i > 0.3, 14.5 < r < 19.0 (N=12)
  • sub-dwarf cands: u-g > 1.8, g-r > 0.8, 0.5 < r-i , 14.5 < r < 19 (N=15)
  • high-velocity M dwarfs: r-i > 0.3, 14.5 < r < 19.3
  • velocity proxy >~ 100 km/s (25)
  • Selection: colorslope (Mdwarfs), high velocity weighted colorslope, colorslope (SubDwarfs)
  • Target count Goal: 50 per plate pair (sum of three sub-categories)
• AGB candidate selection
  • bit -2139095040
  • 14.5 < r < 19.5, 2.5 < u-g < 3.5, 0.9 < g-r < 1.3, s-color < -0.07
  • Selection: colorslope
  • Target count Goal: 15