SEGUE Target Selection

Introduction

Using the photometry from SDSS, the SEGUE survey designed a series of color, magnitude, and other criteria to identify stellar targets that were of particular interest. Each of these spectral types was allotted a certain number of fibers per plate. When targeted by SEGUE, individual targets are labeled with distinctive hexadecimal codes, which indicate which stellar type they are associated with. For a brief explanation of the bitmask system, please use our Bit Guide.

The entire SEGUE survey consists of a number of programs with different observing goals. For example, a number of plates are placed on regions of the sky with open or globular clusters and probable Milky Way substructure (segcluster). An additional number focus on a low latitude region of the sky (seglowlat). The SEGUE Plate Table lists every plate within the SEGUE survey, organized by the program they were a part of, in addition to a brief description of the programs themselves.

Plates which are part of programs other than segue, seguefaint, and segue2 utilize a slightly different target selection algorithm. For example, low latitude plates focus on K giants, with different criteria than K giants observed as part of the segue and seguefaint programs. Additional fibers on these plates, not used to focus on substructure or specific target types, do follow standard target selection algorithm procedures.

The target selection algorithm for SEGUE-1 plates evolved over time. More detailed information on the evolution of target criteria is available on the Past Versions page. Here we list the most current version of the target selection algorithm. These are the criteria used to assign stars to particular spectral categories.

Below, we detail the different targets examined in SEGUE-1, SEGUE-2, and SDSS stellar targeting originating from the SDSS Legacy Program. Each program has a table with summary information for each target type and a description of the different targeting criteria. Finally, we also include a brief summary of the calibration fiber identifications for SEGUE-1, SEGUE-2, and SDSS Stellar Targeting from the Legacy survey.

Jump to Summary Tables for:

SEGUE-1 Target Selection

Example color-color diagram of SEGUE 1 target selection categories.

SEGUE-1 plates are listed here.

The parameter segue1_target1 in sppParams and SpecObjAll is used to identify why a star was given a spectroscopic fiber in SEGUE-1. These same bit settings are used for the segue1_target1 parameter for all stellar objects (g < 21 or z < 21) in the SegueTargetAll table, whether or not they received a SEGUE fiber.

These target selection criteria have evolved over time. We have the latest version (v4.6) here. However, for information about how these have evolved over time, please see Past Versions.

SEGUE-1 v4.6 Target Selection

Summary of SEGUE 1 Target Selection Categories, used in segue1_target1 bitmaps
Category	Hex	Integer	Binary	Criteria	PerPlate	Total	Success
F turnoff, subdwarf	0x80100000	-2146435072	2²⁰	g < 20.3 -0.7 < P1(s) < -0.25 0.4 < (u-g) < 1.4 0.2 < (g-r) < 0.7	200	37900	TBD
K giants (l and red)	0x80004000	-2147467264	2¹⁴	r < 20.2 0.35 < (g-r) < 0.8 0.15 < (r-i) < 0.6 l-color > 0.07 PM_total < 11 mas/yr good PM	70	22814
Low Metallicity	0x80010000	-2147418112	2¹⁶	14 < r < 19.0 -0.5 < (g-r) < 0.75 0.6 < (u-g) < 3.0 l-color > 0.135 u detection	150	29788
Cool White Dwarf	0x80020000	-2147352576	2¹⁷	14.5 < r < 20.5 (g-i) > -2 (g-i) < 1.7 if no neighbor with g > 22 within 7'' Otherwise, (g-r) < 0.12 good PM H_g > 16.05+2.9(g-i) H_g > 17.5	10	1187
White Dwarf	0x80080000	-2146959360	2¹⁹	g < 20.3 -1 < (g-r) < -0.2 -1 < (u-g) < 0.7 (u-g) + 2(g-r) < -0.1	25	4069
K dwarf	0x80008000	-2147450880	2¹⁵	14.5 < r < 19.0 0.55 < (g-r) < 0.75	95	18358
A/Blue Horizontal Branch	0x80002000	-2147475456	2¹³	g < 20.5 0.8 < (u-g) < 1.5 -0.5 < (g-r) < 0.2 u detection Color-gravity index condition	150	24688
F/G	0x80000200	-2147483136	2⁹	g < 20.2 0.2 < (g-r) < 0.48	50	6939
M subdwarfs	0x80400000	-2143289344	2²²	14.5 < r < 19.0 (g-r) > 1.6 0.95 < (r-i) < 1.3	5	1012
L, T brown dwarfs	0x80200000	-2145386496	2²¹	z < 19.5 (i-z) > 1.7 u > 21 g > 22 r > 21	5	1277
AGB	0x80800000	-2139095040	2²³	14.0 < r < 19.0 2.5 < (u-g) < 3.5 0.9 < (g-r) <1.3 s-color < -0.06 u detection	10	1343
G dwarf	0x80040000	-2147221504	2¹⁸	14.0 < r < 20.2 0.48 < (g-r) < 0.55	375	62784
Main Sequence/White dwarf pairs*	0x80001000	-2147479552	2¹²	15.0 < g < 20 (u-g) < 2.25 -0.2 < (g-r) < 1.2 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 (i-z) > 0.68(r-i)-0.18 for (r-i) ≤ 1	5	431
Extreme M subdwarfs*	0x81000000	-2130706432	2²⁴	(r-i) < 0.787(g-r)-0.356 (r-i) < 0.9 H_r >17 1.8 < (g-i) < 2.4	40	9420
Low latitude K giant	0x80000400	-2147482624	2¹⁰	0.55 < (g-r) < 0.9 g < 19 PM_total < 11 mas/yr	300	3220
Low latitude Blue Stellar Locus	0x80000800	-2147481600	2¹¹	(g-r) < 0.25	800	8522
Low latitude AGB/M giants	0x88000000	-2013265920	2²⁷	s-color > -0.13 3.5 > (u-g) > 2.6 0.8 < (g-r) <1.3	50	499

*All magnitudes for MS/WD pairs are the reddened values

Notes:

All ugriz magnitudes listed below are dereddened PSF mags, unless otherwise specified. This means that a check of objc_flag[2] indicates the target has no bright, no edge, no bad interp, no bad deblends
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.
Proper motions have been included for objects which have matches to the USNO-B catalog and are used in various selection categories. Many criteria state "good PM." This uses parameters from the Proper Motions catalog and is defined below:
- Match = 1
- dist22 > 7.0 arcsec (i.e., the nearest neighbor brighter than 22nd magnitude is more than 7'' away)
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 6 (nFit is the number of measurements used in the proper motion fit)
Low Latitude Algorithms implemented:
- AGB type objects at low latitude
- K III type objects at low latitude
- Bluetip objects at low latitude
- AMNH high proper motion objects at low latitude
Principal component color definitions:
- l-color = -0.436u + 1.129g - 0.119r - 0.574i + 0.1984
  and is a photometry metalicity indicator for stars in the color range 0.5 < (g-r) < 0.8.
  Reference: Lenz et al. (1998)
- s-color = -0.249u + 0.794g - 0.555r + 0.234
- P1(s) = P1 = 0.91(u-g) + 0.415(g-r) -1.280
  Reference: Helmi et al. (2003)
- H_g = g + 5 + 5log10(PM (arcsec/year))
- H_r = r + 5 + 5log10(PM (arcsec/year))

SEGUE-1 Target Type Descriptions

The following are the target types included in the SEGUE-1 survey. To jump to a particular target category, please use the links :

White dwarf selection

(bit -2146959360 → 0x80080000)

Color cuts:
- 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 count Goal: 25 per plate pair

Cool White dwarf selection

(bit -2147352576 → 0x80020000)

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 (Good PM):
- one-to-one match to USNO_B
- good proper motion fit (small rms 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
Cuts on reduced proper motion H_g:
- H_g > 17.5
- H_g > 16.05 + 2.9(g-i)
Weighting: magslope 1.2
Target count Goal: 10 per plate pair (but allow overflow if they are present)

A/BHB selection

(bit -2147475456 → 0x80002000)

Color cuts:
- 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, sub-dwarf selection

(bit -2146435072 → 0x80100000)

Color cuts:
- -0.7 < P1(s) < -0.25
- 0.4 < (u-g) < 1.4
- 0.2 < (g-r) < 0.7
- g < 20.3
P1 is a color perpendicular to the locus for F/G/K stars; more negative P1 indicates lower-metallicity side of locus.
Note: there was an s-color cut in versions prior to v3.3, s ≥ -0.065, no longer present for v3.3 and beyond.
Weighting: colorslope+ magnitude weighting P1 min/max slope = 5
Target count Goal: 200 per plate pair

F/G stars

(bit -2147483136 → 0x80000200)

Color cuts:
- 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

G selection

(bit -2147221504 → 0x80040000)

Color cuts:
- 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 count Goal: 375 per plate pair

K Giant Selection

(bit -2147467264 → 0x80004000)

Color cuts:
- 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
PM_total < 11 milliarcsec/year
Good proper motion
Weighting: magslope 2.0
Target count Goal: 95 per plate pair (expected density 4/sq deg = 28/plate pair)

Low Metallicity selection

(bit -2147418112 → 0x80010000)

Color cuts:
- 14 < r < 19.5
- -0.5 < (g-r) < 0.75
- 0.6 < (u-g) < 3.0
- l-color > 0.135
- require detection in u band
Weighting: magslope 1.8. Faint plate targets sorted by magnitude to 'pack' them, so that brightest ones targeted before fainter ones.
Target count Goal: 150 per plate pair

K dwarf selection

(bit -2147450880 → 0x80008000)

Color cuts:
- 14.5 < r < 19.0
- 0.55 < (g-r) < 0.75
Selection: Random subsample
Target count Goal: 95 per plate pair

Main Sequence - White Dwarf pairs

(bit -2147479552 → 0x80001000)

Note that for this category only: colors are NOT dereddened.

Color cuts (from Potsdam group):
- u-g < 2.25
- -0.2 < g-r < 1.2
- 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

M sub-dwarf selection

(bit -2143289344 → 0x80400000)

Color cuts (based on West et al.):
- g-r > 1.6
- 0.95 < (r-i) < 1.3
- 14.5 < r < 19.0
Selection: magslope 0.9
Target count Goal: < ~5 per plate pair
Plus:
- Lepine Shara AMNH high proper motion stars
- Goal 25-30 per plate pair
- Proper motion selected.

L,T brown-dwarf selection

(bit -2145386496 → 0x80200000)

Color cuts:
- z < 19.5
- u > 21
- g > 22
- r > 21
- i-z > 1.7
Note: 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

(bit -2139095040 → 0x80800000)

Color cuts:
- 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
Selection: magslope 1.4
Target count Goal: 10 per plate pair

Extreme M subdwarfs

(bit -2130706432 → 0x81000000)

Color cuts:
- (r-i) < 0.787(g-r)-0.356
- (r-i) < 0.9
- 1.8 < (g-i) < 2.4
- H_r > 17
Selection:
Target count Goal: 40 per plate pair

Low Latitude Targets

The seguelowlat program consists of a number of pointings at |b| < 20, all with E(B-V) > 0.3. These plates required a different target selection algorithm, focusing on the three stellar types listed below.

Low Latitude K Giants

(bit -2147482624 → 0x80000400)

Color cuts:
- 0.55 < (g-r) < 0.9
- g < 19.0
PM_total < 11 mas/yr
Selection:
Target count Goal: 300

Low Latitude Blue Stellar Locus

(bit -2147481600 → 0x80000800)

Color cuts:
- (g-r) < 0.25
- Note that this cut varies with reddening
Selection:
Target count Goal: 800

Low Latitude AGB/M giants

(bit -2013265920 → 0x88000000)

Color cuts:
- 2.6 < (u-g) < 3.5
- 0.8 < (g-r) < 1.3
- s-color > -0.13
Selection:
Target count Goal: 50

Special Targets

Plates 2336, 2337: Special K giant selection

Approximately 200 fibers allocated to objects with
- 0.35 < (g-r) < 0.9
- proper motion consistent with zero.
- No selection boundary parallel to the stellar locus imposed.
Another 200 fibers allocated to random subsample of stellar locus with
- 0.2 < (g-r) < 0.48

These two plates are at (l,b) = (130, -23), (150,+26) respectively, and likely contain Monoceros Giants.

SEGUE-2 Target Selection

The parameter segue2_target1 in sppParams and SpecObjAll is used to identify why a star was given a spectroscopic fiber in SEGUE-2. These same bit settings are used for the segue2_target1 parameter for all stellar objects (g < 21 or z < 21) in the PhotoObjAll table, whether or not they received a SEGUE fiber.

SEGUE-2 plates are listed here.

SEGUE-2 Target Selection

Hex and Decimal values for segue2_target1 bitmaps
Category	Hex	Integer	Binary	Criteria	PerPlate	Total	Success
MS turnoff	0x80000001	-2147483647	2⁰	18 < g < 19.5 0.1 < (g-r) < 0.48 psfmagerr(g,r,i) < 0.05	100	37222	TBD
Red K giants	0x80000002	-2147483646	2¹	15.5 < g < 18.5 r > 15 psfmagerr(g,r,i) < 0.05 good PM 0.8 < (g-r) < 1.3 (u-g) > 0.84(g-r)+1.758 (u-g) < 2.4(g-r)+0.73 PM_total < 11 mas/yr	< 50	1377
l-color K giants	0x80000004	-2147483644	2²	15.5 < g < 18.5 r > 15 psfmagerr(g,r,i) < 0.05 good PM 0.7 < (u-g) < 3 0.5 < (g-r) < 0.8 l-color > 0.09 0.1 < (r-i) < 0.6 PM_total < 11 mas/yr	100	23724
Proper motion only K giants	0x80000008	-2147483640	2³	15.5 < g < 18.5 r > 15 psfmagerr(g,r,i) < 0.05 good PM 0.8 < (u-g) < 1.2 PM_total < 7 mas/yr (u-g) > 2.375(g-r)-0.45 (u-g) < 0.84(g-r)+1.758	150	17872
Low Metallicity	0x80000010	-2147483632	2⁴	0.3 < (g-r) < 0.8 0.5 < (u-g) < 2.0 15.5 < g < 18 r > 15 psfmagerr(g,r,i) < 0.05 psfmagerr(u) < 0.2 l-color > 0.115 good PM	100	16383
Hypervelocity	0x80000020	-2147483616	2⁵	17 < g < 20 PM_total > 8 mas/yr good PM Box 1 criteria or Box 2 criteria	<5	561
Cool Extreme and Ultra Subdwarfs*	0x80000040	-2147483584	2⁶	g > 15.5 (g-r) > 1.4 (r-i) > 0.4 15 < r < 20 (r-i) < 3.0(g-r)-3.5 PM_total < 10 mas/yr H_r > 10.0+2.5(g-r) psfmagerr(r,i) < 0.05 good PM	50	10587
M giants	0x80000080	-2147483520	2⁷	(g-r) > 1.3 (u-g) > 1.8+0.9(g-r) i > 14.5 15.5 < g < 19.25 PM_total < 11 mas/yr psfmagerr(g,r) < 0.05 good PM	<50	631
Halo high velocity	0x80000100	-2147483392	2⁸	17 < g < 20 0.1 < (g-r) < 0.48 V_tan > 300 km/s V_tan/ σ(V_tan) > 3.0	<5	4133
Blue Horizontal Branch	0x80002000	-2147475456	2¹³	15.5 < g < 20.3 -0.5 < (g-r) < 0.1 0.8 < (u-g) < 1.5	< 100	9983
Ultra-Cool CIA White Dwarfs	0x80020000	-2147352576	2¹⁷	15.5 < r < 20.5 g > 15.5 -2.0 < (g-i) > 1.7 good PM H_g > 17.5 H_g > 16.05+2.9(g-i)	< 10	0

*The magnitudes used for cool extreme and ultra subdwarfs are uncorrected for extinction (i.e., reddened).

Notes:

All ugriz magnitudes listed below are dereddened PSF mags, unless otherwise specified. This means that a check of objc_flag[2] indicates the target has no bright, no edge, no bad interp, no bad deblends
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.
Proper motions have been included for objects which have matches to the USNO-B catalog and are used in various selection categories. Many criteria state "good PM." This uses parameters from the Proper Motions catalog and is defined below:
- Match = 1
- dist22 > 7.0 arcsec (i.e., the nearest neighbor brighter than 22nd magnitude is more than 7'' away)
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 6 (nFit is the number of measurements used in the proper motion fit)
Principal component color definitions:
- l-color = -0.436u + 1.129g - 0.119r - 0.574i + 0.1984
  and is a photometry metalicity indicator for stars in the color range 0.5 < (g-r) < 0.8.
  Reference: Lenz et al. (1998)
- s-color = -0.249u + 0.794g - 0.555r + 0.234
- P1(s) = P1 = 0.91(u-g) + 0.415(g-r) -1.280
  Reference: Helmi et al. (2003)
- H_g = g + 5 + 5log10(PM (arcsec/year)) is the reduced proper motion with respect to g.
- H_r = r + 5 + 5log10(PM (arcsec/year)) is the reduced proper motion with respect to r.
- V_tan is the tangential velocity, computed from the measured proper motions and an estimated distance from photometric parallax.
- σ(V_tan) is the error on the tangential velocity calculation, based on the errors of the proper motions and distances.

SEGUE-2 Target Type Descriptions

The following are the target types included in the SEGUE-2 survey. To jump to a particular target category, please use the links :

Blue Horizontal Branch selection

(bit -2147475456 → 0x80002000)

Color cuts:
- 15.5 < g < 20.3
- -0.5 < (g-r) < 0.1
- 0.8 < (u-g) < 1.5
The highest priority BHBs are 15.5 < g < 19.5
- Next highest priority are 19.5 < g < 20.0
- Lowest priority are 20.0 < g < 20.3
This category is given up to 100 fibers per plate but does not always have enough targets to fill its allocation.

Main Sequence Turnoff selection

(bit -2147483647 → 0x80000001)

Color cuts:
- 18.0 < g < 19.5
- 0.1 < (g-r) < 0.48
- g, r, i psfmag errors < 0.05
There are around 1000 objects that pass these criteria per plate region. This category is allotted around 100 fibers.
The magnitude limit is set such that every target will be above the S/N per pix ≥ 10 limit for the SSPP.
The color and magnitude selection for targets given a fiber is a random subsample from the entire candidate pool.

K Giants

Color Cuts:
- 15.5 < g < 18.5
- r > 15.0
- g, r, i psfmag errors < 0.05
Proper Motion Cuts (using parameters in the propermotions table):
- Match = 1
- dist22 > 7.0 arcsec (i.e., the nearest neighbor brighter than 22nd magnitude is more than 7'' away.)
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 6 (number of measurements used in the proper motion fit)

The K giants are then split into three subcategories:

Red K giants
- bit -2147483646 → 0x80000002
- 0.8 < (g-r) < 1.3
- (u-g) > 0.84(g-r)+1.758
- (u-g) < 2.4(g-r)+0.73
- PM_total < 11 mas/yr
- Highest priority targets, up to 50 targets given fibers
l-Color K giants
- bit -2147483644 → 0x80000004
- 0.7 < (u-g) < 3.0
- 0.1 < (r-i) < 0.6
- 0.5 < (g-r) < 0.8
- l-color > 0.09
- PM_total < 11 mas/yr
- Allotted 100 fibers
- Candidates with (g-r) between 0.6 and 0.8 are higher priority than those with (g-r) between 0.5 and 0.6. These redder targets are given fibers first, drawing randomly from the candidate pool. If there are still available fibers, randomly select targets from the bluer sample until you reach up to 100 fibers.
Proper Motion K giants
- bit -2147483640 → 0x80000008
- 0.8 < (u-g) < 1.2
- PM_total < 7 mas/yr
- (u-g) > 2.375(g-r)-0.45
- (u-g) < 0.84(g-r)+1.758
- These targets are supplementary if the other two K giant subcategories do not number 150.

M Giants

(bit -2147483520 → 0x80000080)

Color Cuts:
- (g-r) > 1.3
- (u-g) > 1.8+0.9(g-r)
- i > 14.5
- 15.5 < g < 19.25
- g, r psfmag errors < 0.05
Proper Motion Cuts (using parameters in the propermotions table):
- PM_total < 11 mas/yr
- Match = 1
- dist22 > 7.0 arcsec (i.e., the nearest neighbor brighter than 22nd magnitude is more than 7'' away.)
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 6 (number of measurements used in the proper motion fit)
Candidates with g < 18.5 are highest priority
These are allotted up to 50 fibers, but there are rarely more than 5 candidates per plate region

Cool Extreme and Ultra subdwarfs

(bit -2147483584 → 0x80000040)

Note that all of the magnitudes used for these selection criteria are uncorrected for extinction.

Color Cuts:
- g > 15.5
- (g-r) > 1.4
- (r-i) > 0.4
- 15.0 < r < 20.0
- (r-i < 3.0(g-r)-3.5
- r, i psfmag errors < 0.05
Proper Motion Cuts:
- PM_total > 10 mas/yr
- H_r > 10.0+2.5(g-r)
- Match = 1
- dist22 > 7.0 arcsec (i.e., the nearest neighbor brighter than 22nd magnitude is more than 7'' away.)
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 3 (number of measurements used in the proper motion fit)
These are allotted 50 fibers per plate
If there are more than 50 candidates per plate, they are sorted from reddest to bluest in (g-i) and assigned to fibers in that priority order

Hypervelocity Stars

(bit -2147483392 → 0x80000100)

Color Cuts:
- 17 < g < 20
- Box 1 Cuts:
  - 0.4 < (g-r) < 0.6
  - (u-g) > 2.5(g-r)+0.225
  - (u-g) < 2.5(g-r)+0.425
- Box 2 Cuts:
  - 0.35 < (g-r) < 0.4
  - (u-g) > 2.5(g-r)+0.375
  - (u-g) > 2.5(g-r)+0.525
Proper Motion Cuts:
- PM_total > 8 mas/yr
Assuming motion exactly along the Galactocentric radial direction, all potential targets must have a total space velocity > 400 km/s in a frame at rest with respect to the Galaxy
The candidate is selected if either of the following is also true:
- Assuming GC-radial motion, the proper motion perpendicular to the GC-radial direction is < 6 mas/yr
- The total transverse velocity (at rest with respect to the Galaxy with no assumed direction) is > 400 km/s
This category only has a few targets per plate and is based off of the Kollmeier et al. (2010) paper.

Halo High Velocity Stars

(bit -2147483392 → 0x80000100)

Color Cuts:
- 17.0 < g < 19.5
- 0.1 < (g-r) < 0.48
Proper Motion Cuts:
- V_tan > 300 km/s
- σ(V_tan) > 3.0

Ultra-Cool CIA White Dwarfs

(bit -2147352576 → 0x80020000)

Color Cuts:
- 15.5 < r < 20.5
- g > 15.5
- -2.0 < (g-i) < 1.7
Proper Motion Cuts:
- Match = 1
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- (dist22 > 7.0 arcsec and nfit=6) OR (g-i) < 0.12
- H_g > 17.5
- H_g > 16.05 + 2.9(g-r)
There is some variation in the definition of "good" USNOB proper motions. The distance to the nearest star of 22nd magnitude or brighter neighbor and the nFit cut are relaxed for targets with (g-i) < 0.12 because anything that blue is likely a white dwarf.

Low Metallicity Candidates

(bit -2147483632 → 0x80000010)

Color Cuts:
- 0.3 < (g-r) < 0.8
- 0.5 < (u-g) < 2.0
- 15.5 < g < 18
- r > 15
- g, r, i psfmag errors < 0.05
- u psfmag errors < 0.2
- l-color > 0.115
Proper Motion Cuts:
- Match = 1
- dist22 > 7.0 arcsec
- pmSigmaRa < 525 mas/yr
- pmSigmaDec < 525 mas/yr
- nFit = 6
Candidates with PM_total > 20 mas/yr are the highest priority
All other candidates are lower priority and assigned fibers until reaching the allotted 100 fibers per plate.

SDSS Cluster Plate Targeting

A number of SEGUE plates (mostly in SEGUE-1, but also in SEGUE-2) specificially targeted on known globular or open clusters. Since these clusters are generally quite bright, the exposure times of these plates were often shorter than the normal 45 min to 2 hours exposure time, in some cases as short as two minutes. Such a short exposure time can result in lack of sky signal, and the wavelength calibration for these plates as well as the spectrophotometric flux calibration must be carefully be done by hand. While we have taken many precautions in getting these calibrations correct, users are cautioned to regard these with care. The spectra and measured SSPP output parameters from these cluster stars, combined with their ugriz or other photometry is the basis for putting the log(g), [Fe/H] and T_eff systems on uniform system. The list of plates targeted in this fashion with their target cluster is here.

SDSS Stellar Targeting - Legacy

Approximately 200,000 stars were spectroscopically observed as part of the SDSS and SDSS-II Legacy program. These targets are briefly described in Yanny et al. 2009,and the target categories are explained in Stoughton et al. 2002 There is a brief description of the overall Legacy target selection algorithm here.

The table below lists the possible legacy1_target1 (located in the sppParams and SpecObjAll tables) bit settings available on each spectrum if this object was a Legacy target. Unlike SEGUE-1 and SEGUE-2, every target in the Legacy component is identified by the target type criteria it fulfills, rather than why it was assigned a fiber.

SDSS Stellar Targeting Selection Categories
Category	Hex	Integer	Binary	Color, Mag Cuts	Total Fibers
Spectrophotometric Standard	0x00000020	32	2⁵	0.1 < (g-r) < 0.4 16 < g < 17.1	20320
Reddening Standard	0x00000002	2	2¹	0.1 < (g-r) < 0.4 17.1 < g < 18.5	22337
Hot Standard	0x00000200	512	2⁹	g < 19 (u-g) < 0 (g-r) < 0	3370
ROSAT C	0x00000800	2048	2¹¹	r < 16.5 ROSAT X-ray source within 60'' (u-g) < 1.1	8000
ROSAT E	0x08000000	134217728	2²⁷	ROSAT source within 60''	8000
BHB Star	0x00002000	8192	2¹³	-0.4 < (g-r) < 0 0.8 < (u-g) < 1.8	19887
Carbon Star	0x00004000	16384	2¹⁴	(g-r) > 0.85 (r-i) > 0.05 (i-z) > 0 (r-i) < -0.4+0.65(g-r) (g-r) > 1.75	4453
Brown Dwarf	0x00008000	32768	2¹⁵	z < 19 psfmagerr(i) < 0.3 (r-i) > 1.8 (i-z) > 1.8	667
Subdwarf	0x00010000	65536	2¹⁶	(g-r) > 1.6 0.95 < (r-i) < 1.6 psfmagerr(g) < 0.1	1482
Catyclismic Variable*	0x00020000	131072	2¹⁷	g < 19.5 (u-g) < 0.45 (g-r) < 0.7 (r-i) > 0.3 (i-z) > 0.4 (u-g)-1.314(g-r) < 0.61 (r-i) > 0.91 (i-z) > 0.49	8959
Red Dwarf	0x00040000	262144	2¹⁸	i < 19.5 psfmagerr(i) < 0.2 (r-i) > 1.0 (r-i) > 1.8	14649
White Dwarf	0x00080000	524288	2¹⁹	(g-r) < -0.15 (u-g)+2(g-r) < 0 (r-i) < 0 H_g > 19 H_g > 16.136 + 2.727(g-i) (g-i) > 0	6059
PN Star	0x10000000	268435456	2²⁸	(g-r) > 0.4 (r-i) < -0.6 (i-z) > -0.2 16 < r < 20.5	20
Serendipity Blue	0x00100000	1048576	2²⁰	(u-g) < 0.8 (g-r) < -0.05	81937
Serendipity FIRST	0x00200000	2097152	2²¹	FIRST radio source within 1.5''	14689
Serendipity Red*	0x00400000	4194304	2²²	(r-i) > 2.7 (i-z) > 1.6	4179
Serendipity Distant*	0x00800000	8388608	2²³	(g-r) > 2 (r-i) < 0	11820

*The magnitudes for these targets are not dereddened.

SDSS Stellar Targeting Category Descriptions

The following are the target types included in the SDSS Legacy survey. To jump to a particular target category, please use the links :

Spectrophotometric Standard

(bit 32 → 0x00000020)

0.1 < (g-r) < 0.4
16.0 < g < 17.1

Reddening Standard

(bit 2 → 0x00000002)

0.1 < (g-r) < 0.4
17.1 < g < 18.5

Hot Standard

(bit 512 → 0x00000200)

g < 19
(g-r) < 0
(u-g) < 0

ROSAT C

(bit 2048 → 0x00000800)

r < 16.5
(u-g) < 1.1
ROSAT within 60''

ROSAT E

(bit 134217728 → 0x08000000)

ROSAT within 60''

Red dwarf

(bit 262144 → 0x00040000)

i < 19.5
psfmagerr(i) < 0.2
(r-i) > 1.0
(r-i) > 1.8

Planetary Nebula Star

(bit 268435456 → 0x10000000)

(g-r) > 0.4
(r-i) < 0.6
(i-z) > -0.2
16 < r < 20.5

Serendipity Blue

(bit 1048576 → 0x00100000)

(u-g) < 0.8
(g-r) < -0.05

Serendipity Red

(bit 4194304 → 0x00400000)

(r-i) > 2.7
(i-z) > 1.6
Colors for the above criteria are not dereddened

Blue Horizontal Branch

(bit 8192 → 0x00002000)

-0.4 < (g-r) < 0
0.8 < (u-g) < 1.8

Carbon Star

(bit 16384 → 0x00004000)

(r-i) > 0.05
(g-r) > 0.85
(i-z) > 0
(r-i) < -0.4 + 0.65(g-r)
(g-r) < 1.75

Brown dwarf

(bit 32768 → 0x00008000)

z < 19
psfmagerr(i) < 0.3
(r-i) > 1.8
(i-z) > 1.8

Subdwarf

(bit 65536 → 0x00010000)

(g-r) > 1.6
0.95 < (r-i) < 1.6
psfmagerr(g) < 0.1

Cataclysmic Variable

(bit 131072 → 0x00020000)

g < 19.5
(u-g) < 0.45
(g-r) < 0.7
(r-i) > 0.3
(i-z) > 0.4
(u-g)-1.314(g-r) < 0.61
(r-i) > 0.91
(i-z) > 0.49
Magnitudes are not dereddened for this category.

White dwarf

(bit 524288 → 0x00080000)

(g-r) < -0.15
(u-g)+2(g-r) < 0
(r-i) < 0
(g-i) > 0
H_g > 19
H_g > 16.136+2.727(g-i)

Serendipity First

(bit 2097152 → 0x00200000 )

FIRST Radio source within 1''.5

Serendipity Distant

(bit 8388608 → 0x00800000)

(g-r) > 2
(r-i) < 0
Magnitudes are not dereddened for this category.

Calibration Fibers in SEGUE-1 and SEGUE-2

A number of stellar targets are assigned fibers for calibration purposes. This is indicated in the parameter segue1_target2 in the SpecObjAll and sppParams tables for SEGUE-1 targets and in segue2_target2 for SEGUE-2.

The bitmask assignments for segue1_target2 are listed below:

Hex and Integer values for segue1_target2 bitmasks
Category	Hex	Integer	Binary
Science Target	0x40000000	1073741824	2³⁰
Reddening Standard	0x2	2	2¹
QA Duplicate Observation*	0x8	8	2³
Sky	0x10	16	2⁴
Spectrophotometric Standard	0x20	32	2⁵

The bitmask assignments for segue2_target2 are listed below:

Hex and Integer values for segue2_target2 bitmaps
Category	Hex	Integer	Binary
Light Trap	0x80000001	-2147483647	2⁰
Reddening Standard	0x80000002	-2147483646	2¹
Test	0x80000004	-2147483644	2²
QA Duplicate Observation*	0x80000008	-2147483640	2³
Sky	0x80000010	-2147483632	2⁴
Spectrophotometric Standard	0x80000020	-2147483616	2⁵
Guide Star	0x80000040	-2147483584	2⁶
Bundle Hole	0x80000080	-2147483520	2⁷
Quality Hole	0x80000100	-2147483392	2⁸
Hot Standard	0x80000200	-2147483136	2⁹
Stellar Cluster Target	0x80000400	-2147482624	2¹⁰
Stetson Standard	0x80000800	-2147481600	2¹¹

*QA duplicate observations are not currently marked in segue1_target2 bitmasks. These are only marked in objtype in SpecObjAll.