FURTHER DEFINING SPECTRAL TYPE “Y” AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION

By J. Davy Kirkpatrick, C. Gelino, M. Cushing, G. Mace, R. Griffith, M. Skrutskie, Kenneth A. Marsh, E. L. Wright, Peter Eisenhardt, I. McLean and 5 more. 2012

248 citations recorded by the source corpus.

We present the discovery of another seven Y dwarfs from the Wide-field Infrared Survey Explorer (WISE). Using these objects, as well as the first six WISE Y dwarf discoveries from Cushing et al., we further explore the transition between spectral types T and Y. We find that the T/Y boundary roughly coincides with the spot where the J − H colors of brown dwarfs, as predicted by models, turn back to the red. Moreover, we use preliminary trigonometric parallax measurements to show that the T/Y boundary may also correspond to the point at which the absolute H (1.6 μm) and W2 (4.6 μm) magnitudes plummet. We use these discoveries and their preliminary distances to place them in the larger context of the solar neighborhood. We present a table that updates the entire stellar and substellar constituency within 8 pc of the Sun, and we show that the current census has hydrogen-burning stars outnumbering brown dwarfs by roughly a factor of six. This factor will decrease with time as more brown dwarfs are identified within this volume, but unless there is a vast reservoir of cold brown dwarfs invisible to WISE, the final space density of brown dwarfs is still expected to fall well below that of stars. We also use these new Y dwarf discoveries, along with newly discovered T dwarfs from WISE, to investigate the field substellar mass function. We find that the overall space density of late-T and early-Y dwarfs matches that from simulations describing the mass function as a power law with slope −0.5 < α < 0.0; however, a power law may provide a poor fit to the observed object counts as a function of spectral type because there are tantalizing hints that the number of brown dwarfs continues to rise from late-T to early-Y. More detailed monitoring and characterization of these Y dwarfs, along with dedicated searches aimed at identifying more examples, are certainly required.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cfdd483a579ebf695f31d9788ea2932286077660

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In Astronomy and Astrophysics

1. Michael C. Liu
2. T. Dupuy
3. M. Marley
4. A. Burgasser
5. K. Luhman
6. Jon Fortney
7. B. Bowler
8. K. Allers

In Instrumentation

1. Michael C. Liu
2. T. Dupuy
3. A. Burgasser
4. M. Marley
5. K. Luhman
6. J. D. Kirkpatrick
7. K. Allers
8. B. Bowler

Citations in the corpus

• DISCOVERY OF A BINARY BROWN DWARF AT 2 pc FROM THE SUN (2013, background): “For comparison, I have included a sample of known M, L, and T dwarfs (Leggett et al. 2010; Kirkpatrick et al. 2011, 2012, http://DwarfArchives.org).”
• KELT-1b: A STRONGLY IRRADIATED, HIGHLY INFLATED, SHORT PERIOD, 27 JUPITER-MASS COMPANION TRANSITING A MID-F STAR (2012, unknown): “…to KELT-1 and thus at the same distance of 262±14pc and suffers the same extinction ofAV = 0.18±0.10 (see §5.1), then we estimate its absoluteH magnitude to beMH = 8.31±0.15, corresponding to a M4-5 spectral type, consistent with its color (see, e.g., the compilation of Kirkpatrick et al. 2012).”
• BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, unknown): “…Deacon et al. (2014); Delorme et al. (2008a,b); Dieterich et al. (2014); Faherty et al. (2013); Hawley et al. (2002); Kendall et al. (2007b,a); Kirkpatrick et al. (2012); Leggett et al. (2000, 2002, 2009, 2010, 2013, 2015); Lodieu et al. (2005, 2007); Looper et al. (2007b,a); Lucas et al.…”
• A T8.5 BROWN DWARF MEMBER OF THE ξ URSAE MAJORIS SYSTEM (2012, background): “However, the absolute magnitude of the components would no longer agree with the MW2 vs. type relation (Kirkpatrick et al. 2011, 2012).”
• STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “On the other hand, the ratio of the number of main-sequence stars with m 1 (almost all of which have m 0.08> ) to the number of brown dwarfs in the Kirkpatrick et al. (2012) catalog of stars within 8 pc (almost all of which are in the mass range m0.”
• Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report (2015, background): “A puzzling discovery from WISE surveys is a severe deficiency of brown dwarfs within the local volume, D < 8 pc: 33 brown dwarfs versus 211 normal stars is far less than typically predicted ratio of ~ 1:1 (Kirkpatrick et al. 2012).”
• PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “…at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. neighborhood they make up ≈75% of stars (Henry et al. 2006; Kirkpatrick et al. 2012), which is a good estimate for their galactic-wide rate (Bochanski et al. 2010), and there is some evidence that M dwarfs…”
• CLASH: THREE STRONGLY LENSED IMAGES OF A CANDIDATE z ≈ 11 GALAXY (2012, methodology): “The coldest dwarfs yet discovered are Y dwarfs including WISEP J1828+2650 at ∼300 K (Cushing et al. 2011; Kirkpatrick et al. 2012) with colors as plotted in Fig.”
• A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE (2013, methodology): “Kirkpatrick et al. (2012) use this information to determine absolute magnitude relationships and constrain the mass function.”
• An Accurate, Extensive, and Practical Line List of Methane for the HITEMP Database (2020, background): “E P] 1 4 Ja (Cushing et al. 2011; Kirkpatrick et al. 2012) and is also present in the atmospheres of the giant planets (Irwin et al. 2005; Mueller-Wodarg et al. 2008) and Titan (Karkoschka 1994; Atreya et al. 2006).”
• Imaging Extrasolar Giant Planets (2016, background): “…et al. 2009a; Scholz et al. 2012; Muzic et al. 2015), among closer young stellar associations (Liu et al. 2013; Gagné et al. 2015a; Kellogg et al. 2016; Schneider et al. 2016), and at much older ages as Y dwarfs in the field (Cushing et al. 2011; Kirkpatrick et al. 2012; Beichman et al. 2013).”
• IMPROVED ESTIMATES OF THE MILKY WAY’S STELLAR MASS AND STAR FORMATION RATE FROM HIERARCHICAL BAYESIAN META-ANALYSIS (2014, unknown): “005 M 0.01< <⊙ ) from −0.5 to 0.5 (Cruz et al. 2007; Kirkpatrick et al. 2012; Burningham et al. 2013; Day-Jones et al. 2013) and including their contribution within the Bruzual & Charlot (2003) model using solar metallicity and the Kroupa IMF over the main-sequence mass range.”
• Individual Dynamical Masses of Ultracool Dwarfs (2017, background): “Age Distribution The age distribution of the field population provides information about the star formation history of the galaxy and is a key component in studies of substellar mass function in the solar neighborhood (e.g., Burningham et al. 2010; Kirkpatrick et al. 2012).”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…al. (2005), (14) Naud et al. (2014), (15) Marocco et al. (2010), (16) Tinney (1996), (17) van Altena et al. (1995), (18) Patten et al. (2006), (19) Kirkpatrick et al. (2012), (20) Costa et al. (2006), (21) Monet et al. (1992), (22) Gelino et al. (2014), (23) Andrei et al. (2011), (24) Thorstensen…”
• NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES (2012, methodology): “We also showJ, H, K and Spitzer photometry (Lucas et al. 2010) and WISE photometry (Kirkpatrick et al. 2012).”
• The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs (2020, methodology): “…as the online list1 of the top one hundred closest systems – which as of the last update in 2012 extends to a radius of 6.95 pc from the Sun – by the Research Consortium On Nearby Stars (RECONS) team, or the 8-pc census presented by Kirkpatrick et al. (2012) that contained 243 individual objects.”