Herschel-Planck dust optical depth and column density maps II. Perseus

We present optical depth and temperature maps of the Perseus molecular cloud, obtained combining dust emission data from the Herschel and Planck satellites and 2MASS/NIR dust extinction maps. The maps have a resolution of 36 arcsec in the Herschel regions, and of 5 arcmin elsewhere. The dynamic range of the optical depth map ranges from 1 x 10(-2) mag up to 20 mag in the equivalent K-band extinction. We also evaluate the ratio between the 2.2 mu m extinction coefficient and the 850 mu m opacity. The value we obtain is close to the one found in the Orion B molecular cloud. We show that the cumulative and the differential area function of the data ( which is proportional to the probability distribution function of the cloud column density) follow power laws with an index of respectively similar or equal to-2, and similar or equal to-3. We use WISE data to improve current YSO catalogs based mostly on Spitzer data and we build an up-to-date selection of Class I/0 objects. Using this selection, we evaluate the local Schmidt law, Sigma(YSO) proportional to Sigma(beta)(gas), showing that beta = 2.4 +/- 0.6. Finally, we show that the area-extinction relation is important for determining the star-formation rate in the cloud, which is in agreement with other recent works.