TY - JOUR
T1 - L dwarfs and the substellar mass function
AU - Reid, I. Neill
AU - Kirkpatrick, J. Davy
AU - Liebert, J.
AU - Burrows, Adam S.
AU - Gizis, J. E.
AU - Burgasser, A.
AU - Dahn, C. C.
AU - Monet, D.
AU - Cutri, R.
AU - Beichman, C. A.
AU - Skrutskie, M.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1999/8/20
Y1 - 1999/8/20
N2 - Analysis of initial observations sky surveys has shown that the resulting photometric catalogs, combined with far-red optical data, provide an extremely effective method of finding isolated, very low-temperature objects in the general field. Follow-up observations have already identified more than 25 sources with temperatures cooler than the latest M dwarfs. A comparison with detailed model predictions (Burrows & Sharp 1999) indicates that these L dwarfs have effective temperatures between ≈ 2000 ± 100 K and 1500 ± 100 K, while the available trigonometric parallax data place their luminosities at between 10-3.5 and 10. Those properties, together with the detection of lithium in one-third of the objects, are consistent with the majority having substellar masses. The mass function cannot be derived directly, since only near-infrared photometry and spectral types are available for most sources, but we can incorporate VLM/brown dwarf models in simulations of the solar neighborhood population and constrain Ψ(M) by comparing the predicted L dwarf surface densities and temperature distributions against observations from the Deep Near-Infrared Survey (DENIS) and 2 Micron All-Sky Survey (2MASS) surveys. The data, although sparse, can be represented by a power-law mass function, Ψ(M) ∝ M-α, with 1 < α < 2. Current results favor a value nearer the lower limit. If α = 1.3, then the local space density of 0.075 > M/M⊙ > 0.01 brown dwarfs is 0.10 systems pc-3. In that case, brown dwarfs are twice as common as main-sequence stars but contribute no more than ∼15% of the total mass of the disk.
AB - Analysis of initial observations sky surveys has shown that the resulting photometric catalogs, combined with far-red optical data, provide an extremely effective method of finding isolated, very low-temperature objects in the general field. Follow-up observations have already identified more than 25 sources with temperatures cooler than the latest M dwarfs. A comparison with detailed model predictions (Burrows & Sharp 1999) indicates that these L dwarfs have effective temperatures between ≈ 2000 ± 100 K and 1500 ± 100 K, while the available trigonometric parallax data place their luminosities at between 10-3.5 and 10. Those properties, together with the detection of lithium in one-third of the objects, are consistent with the majority having substellar masses. The mass function cannot be derived directly, since only near-infrared photometry and spectral types are available for most sources, but we can incorporate VLM/brown dwarf models in simulations of the solar neighborhood population and constrain Ψ(M) by comparing the predicted L dwarf surface densities and temperature distributions against observations from the Deep Near-Infrared Survey (DENIS) and 2 Micron All-Sky Survey (2MASS) surveys. The data, although sparse, can be represented by a power-law mass function, Ψ(M) ∝ M-α, with 1 < α < 2. Current results favor a value nearer the lower limit. If α = 1.3, then the local space density of 0.075 > M/M⊙ > 0.01 brown dwarfs is 0.10 systems pc-3. In that case, brown dwarfs are twice as common as main-sequence stars but contribute no more than ∼15% of the total mass of the disk.
KW - Galaxy: stellar content
KW - Stars: low-mass, brown dwarfs
KW - Stars: luminosity function, mass function
KW - Stars: statistics
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U2 - 10.1086/307589
DO - 10.1086/307589
M3 - Article
AN - SCOPUS:0033587883
VL - 521
SP - 613
EP - 629
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 PART 1
ER -