New Brown Dwarfs and an Updated Initial Mass Function in Taurus

I have performed a search for young low-mass stars and brown dwarfs (BDs) in 2 regions encompassing a total area of 4 deg² in the Taurus star-forming region, discovering 15 new members of Taurus. In addition, I present 7 new members outside of these areas from the initial stage of a survey of all of Taurus. These 22 objects exhibit spectral types of M4. 5-M9. 25 and masses of 0. 3-0. 015 Mₛun according to the theoretical evolutionary models of Baraffe and Chabrier, 7 of which are likely to be BDs. Emission in H (alpha), He I, Ca II, O I, and S II and excess emission in optical and near-IR bands among some of these objects suggest the presence of accretion, outflows, and circumstellar disks. The results from the 4 deg² survey have been combined with previous studies of Taurus to arrive at an IMF for a total area of 12. 4 deg². As in the previous IMFs for Taurus, the updated IMF peaks at a higher mass (0. 8 Mₛun) than the mass functions in IC 348 and Orion (0. 1-0. 2 Mₛun). Meanwhile, the deficit of BDs in Taurus appears to be less significant (x1. 4-1. 8) than found in earlier studies (x2) because of a slightly higher BD fraction in the new IMF for Taurus and a lower BD fraction in the new spectroscopic IMF for the Trapezium from Slesnick and coworkers. The spatial distribution of the low-mass stars and BDs discovered in the two new survey areas closely matches that of the more massive members. Thus, on the degree size scales (~3 pc) probed to date, there is no indication that BDs form through ejection. Finally, I draw attention to the misleading nature of the recent claim of Barrado y Navascues to have "confirmed" a sample of late-type objects as members of Taurus, which were already conclusively determined to be bonafide members in the discovery paper by Briceno and coworkers.