TY - JOUR

T1 - Fractal dimension of optical cirrus in Stripe82

AU - Marchuk, Alexander A.

AU - Smirnov, Anton A.

AU - Mosenkov, Aleksandr V.

AU - Ilin, Vladimir B.

AU - Gontcharov, George A.

AU - Savchenko, Sergey S.

AU - Roman, Javier

N1 - Publisher Copyright: © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

PY - 2021/12/1

Y1 - 2021/12/1

N2 - The geometric characteristics of dust clouds provide important information on the physical processes that structure such clouds. One of such characteristics is the 2D fractal dimension D of a cloud projected on to the sky plane. In previous studies, which were mostly based on infrared (IR) data, the fractal dimension of individual clouds was found to be in a range from 1.1 to 1.7 with a preferred value of 1.2-1.4. In this work, we use data from Stripe82 of the Sloan Digital Sky Survey to measure the fractal dimension of the cirrus clouds. This is done here for the first time for optical data with significantly better resolution as compared to IR data. To determine the fractal dimension, the perimeter-area method is employed. We also consider IR (IRAS and Herschel) counterparts of the corresponding optical fields to compare the results between the optical and IR. We find that the averaged fractal dimension across all clouds in the optical is $\langle D \rangle =1.69{+0.05} {-0.05}$ which is significantly larger than the fractal dimension of its IR counterparts $\langle D\rangle =1.38{+0.07} {-0.06}$. We examine several reasons for this discrepancy (choice of masking and minimal contour level, image and angular resolution, etc.) and find that for approximately half of our fields the different angular resolution (point spread function) of the optical and IR data can explain the difference between the corresponding fractal dimensions. For the other half of the fields, the fractal dimensions of the IR and visual data remain inconsistent, which can be associated with physical properties of the clouds, but further physical simulations are required to prove it.

AB - The geometric characteristics of dust clouds provide important information on the physical processes that structure such clouds. One of such characteristics is the 2D fractal dimension D of a cloud projected on to the sky plane. In previous studies, which were mostly based on infrared (IR) data, the fractal dimension of individual clouds was found to be in a range from 1.1 to 1.7 with a preferred value of 1.2-1.4. In this work, we use data from Stripe82 of the Sloan Digital Sky Survey to measure the fractal dimension of the cirrus clouds. This is done here for the first time for optical data with significantly better resolution as compared to IR data. To determine the fractal dimension, the perimeter-area method is employed. We also consider IR (IRAS and Herschel) counterparts of the corresponding optical fields to compare the results between the optical and IR. We find that the averaged fractal dimension across all clouds in the optical is $\langle D \rangle =1.69{+0.05} {-0.05}$ which is significantly larger than the fractal dimension of its IR counterparts $\langle D\rangle =1.38{+0.07} {-0.06}$. We examine several reasons for this discrepancy (choice of masking and minimal contour level, image and angular resolution, etc.) and find that for approximately half of our fields the different angular resolution (point spread function) of the optical and IR data can explain the difference between the corresponding fractal dimensions. For the other half of the fields, the fractal dimensions of the IR and visual data remain inconsistent, which can be associated with physical properties of the clouds, but further physical simulations are required to prove it.

KW - dust, extinction

KW - ISM: clouds

KW - MACH NUMBER

KW - DUST

KW - ORIGIN

KW - INFRARED CIRRUS

KW - MOLECULAR CLOUDS

KW - GAS

KW - EMISSION

KW - EXTINCTION

KW - SUPERSONIC TURBULENCE

UR - http://www.scopus.com/inward/record.url?scp=85119498002&partnerID=8YFLogxK

U2 - 10.1093/mnras/stab2846

DO - 10.1093/mnras/stab2846

M3 - Article

AN - SCOPUS:85119498002

VL - 508

SP - 5825

EP - 5841

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -