2MASS wide field extinction maps. III. The Taurus, Perseus, and California cloud complexes

Abstract. We present a near-infrared extinction map of a large region in the sky (~ 3500 deg²) in the general directions of Taurus, Perseus, and Aries. The map has been obtained using robust and optimal methods to map dust column density at near-infrared wavelengths (Nicer, described in Lombardi & Alves 2001, A&A, 377, 1023 and Nicest, described in Lombardi 2009, A&A, 493, 735) toward ~23 million stars from the Two Micron All Sky Survey (2MASS) point source catalog. We measure extinction as low as A_K = 0.04 mag with a 1-σ significance, and a resolution of 2.5 arcmin in our map. A 250 deg² section of our map encompasses the Taurus, Perseus, and California molecular cloud complexes. We determine the distances of the clouds by comparing the observed density of foreground stars with the prediction of galactic models, and we obtain results that are in excellent agreement with recent VLBI parallax measurements. We characterize the large-scale structure of the map and find a ~ 25° × 15° region close to the galactic plane (l ~ 135°, b ~ -14°) with small extinction (AK < 0.04 mag); we name this region the Perseus-Andromeda hole. We find that over the region that encompasses the Taurus, Perseus, and California clouds the column density measurements below AK < 0.2 mag are perfectly described by a log-normal distribution, and that a significant deviation is observed at larger extinction values. If turbulence models are invoked to justify the log-normal distribution, the observed departure could be interpreted as the result of the effect of gravity that acts on the cores of the clouds. Finally, we investigate the cloud structure function, and show that significant deviations from the results predicted by turbulent models are observed in at least one cloud.

A NICER extinction map of the Taurus, Perseus, and California dark nebulae.

The probability density function for the extinction measurements obtained in the region above. The fit with a log-normal distribution is almost perfect, with an excess at high-column densities where star formation occurs.