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- Ancillary Targets
- Transient Universe in Stripe 82
- Host Galaxies of SDSS-II SNe
- BCGs in
Stripe 82 - High-Quality LRG spectra
- Reddened
Quasars - No Quasar Left Behind
- Variability-Selected Quasars
- K-band Selected Quasars
- Low-Mass Stars and Brown Dwarfs
- Low-Mass Binary Stars
- White Dwarfs and Hot Subdwarfs
- Distant Halo
Giants - Bright
Galaxies - High-Energy Blazars in Optical
- An X-Ray View Star Formation
- Remarkable X-Ray Sources
- Star-Forming Radio Galaxies
- Galaxies Near QSO Sight Lines
- Luminous Blue Galaxies
- BAL Quasar Variability
- Variable QSO Absorption
- Double-Lobed Radio QSOs
- High-Redshift Quasars
- High-z QSOs in SDSS/UKIDSS
- BOSS Targeting
- Algorithms
Very Low-Mass Stars and Brown Dwarfs
Summary
A search for M stars and L dwarfs in the BOSS survey area (7,650 square degrees)
Finding Targets
An object whose ANCILLARY_TARGET1 value includes one or more of the bitmasks
in the following table was targeted for spectroscopy as part of this ancillary target
program. See SDSS-III bitmasks to learn how to use
these values to identify objects in this ancillary target program.
| Program (bit name) | Bit | Target Description | Survey area (deg2) | Target density (deg–2) |
|---|---|---|---|---|
| BRIGHTERL | 44 | Bright L dwarf candidates | 220 | 0.07 |
| 7,650 | 0.08 | |||
| BRIGHTERM | 45 | Bright M star candidates | 220 | 2.9 |
| 7,650 | 0.3 | |||
| FAINTERL | 46 | Faint L dwarf candidates | 220 | 0.3 |
| 7,650 | 0.2 | |||
| FAINTERM | 47 | Faint M star candidates | 220 | >2.2 |
| 7,650 | 0.6 |
Primary contact
| Suzanne Hawley |
|---|
| University of Washington |
| slh -at- astro.washington.edu |
Other contacts
Sarah Schmidt, Andrew West, John Bochanski
Description
Very-low-mass stars and brown dwarfs (spectral types M8, M9 and L) are ideal tracers of the kinematic properties of the Milky Way thin disk. While the program The Transient Universe Through Stripe 82 uses variability information over Stripe 82 to identify rare classes of stars, this ancillary target program uses photometric selection over the much larger BOSS survey area to identify new low-mass stars and brown dwarfs.
SDSS-I and SDSS-II yielded a wealth of spectroscopic data of these ultracool dwarfs (Schmidt et al. 2010b; West et al. 2011), but were limited by the small number of spectra observed for stars with spectral types later than M7. Additional observations of these objects are essential to understand the properties of magnetic activity in these ultracool dwarfs (extending the results of West et al. 2008). The data will also enable studies using kinematics to understand the distribution of stellar ages, especially at the stellar/sub-stellar boundary. Finally, the sample will contain a class of L dwarfs which are peculiarly blue in the near-infrared, but have typical L dwarf colors in SDSS i - z (Schmidt et al. 2010a).
Target Selection Details
The ancillary target program was divided into two survey areas: the stripe 82 footprint (with target density 5 deg-2) and the overall BOSS footprint (with target density 1 deg-2). Within the stripe 82 footprint, targets were sought at five per square degree; in the rest of the BOSS footprint, targets were sought at one per square degree. To select the cleanest possible sample, the photometric selection criteria included 2MASS magnitudes.
The target selection criteria in the stripe 82 footprint are:
- iPSF - zPSF > 1.14
- iPSF < 21
- iPSF - J > 3.7
- 1.9 < zPSF - J < 4
Criteria for the rest of the BOSS footprint are:
- iPSF - zPSF > 1.44
- iPSF < 20.5
- iPSF - J > 3.7
- 1.9 < zPSF - J < 4
Here, the J-band photometry, unlike the SDSS photometry, is Vega-based.
In both survey areas, targets are divided into subsamples with different priorities. L dwarfs are both less common and fainter, so our priority was to detect L dwarfs over late-M dwarfs. Targets likely to be bright L dwarfs are indicated by the BRIGHTERL sub-program, and are assigned first priority. Fainter L dwarfs (FAINTERL) are assigned second priority. Lower priorities are assigned to likely M dwarfs, both brighter (BRIGHTERM) and fainter (FAINTERM).
The selection criteria used to assign targets to each of the four sub-programs is:
| Sub-program | Magnitude cut | Color cut |
|---|---|---|
| BRIGHTERL | iPSF < 19.5 | iPSF - zPSF > 1.14 |
| FAINTERL | iPSF > 19.5 | iPSF - zPSF > 1.14 |
| BRIGHTERM | iPSF < 19.5 | iPSF - zPSF < 1.14 |
| FAINTERM | iPSF < 19.5 | iPSF - zPSF < 1.14 |
REFERENCES
Schmidt, S. J., West, A. A., Burgasser, A. J., Bochanski, J. J., & Hawley, S. L. 2010a, AJ, 139, 1045
Schmidt, S. J., West, A. A., Hawley, S. L., & Pineda, J. S. 2010b, AJ, 139, 1808
West, A. A., Hawley, S. L., Bochanski, J. J., Covey, K. R., Reid, I. N., Dhital, S., Hilton, E. J., & Masuda, M. 2008, AJ, 135, 785
West, A. A., et al. 2011, AJ, 141, 97