Multilognormal density structure in Cygnus-X molecular clouds: a fitting for N-PDF without power law

Author:

Murase Takeru1ORCID,Handa Toshihiro12,Matsusaka Ren1,Shimajiri Yoshito345,Kobayashi Masato I N36,Kohno Mikito78,Nishi Junya1,Takeba Norimi1ORCID,Shibata Yosuke1

Affiliation:

1. Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University , 1-21-35 Kôrimoto, Kagoshima, Kagoshima 890-0065, Japan

2. Amanogawa Galaxy Astronomy Research centre, Kagoshima University , 1-21-35 Kôrimoto, Kagoshima, Kagoshima 890-0065, Japan

3. National Astronomical Observatory of Japan , Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan

4. Laboratoire d’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot , Sorbonne Paris Cité, F-91191 Gif-sur-Yvette, France

5. Centre for General Education, Kyushu Kyoritsu University , Jiyugaoka 1-8, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8585, Japan

6. Physikalisches Institut, Universität zu Köln , ZülpicherStr 77, 50937 Köln, Germany

7. Astronomy Section, Nagoya City Science Museum , 2-17-1 Sakae, Naka-ku, Aichi, Nagoya 460-0008, Japan

8. Department of Physics, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Aichi, Nagoya 464-8602, Japan

Abstract

ABSTRACT We studied the H2 column density probability distribution function (N-PDF) based on molecular emission lines using the Nobeyama 45-m Cygnus X CO survey data. Using the DENDROGRAM and SCIMES algorithms, we identified 124 molecular clouds in the 13CO data. From these identified molecular clouds, an N-PDF was constructed for 11 molecular clouds with an extent of more than 0.4 deg2. From the fitting of the N-PDF, we found that the N-PDF could be well fitted with one or two lognormal distributions. These fitting results provided an alternative density structure for molecular clouds from a conventional picture. We investigated the column density, dense molecular cloud cores, and radio continuum source distributions in each cloud and found that the N-PDF shape was less correlated with the star-forming activity over a whole cloud. Furthermore, we found that the lognormal N-PDF parameters obtained from the fitting showed two impressive features. First, the lognormal distribution at the low-density part had the same mean column density (∼1021.5 cm−2) for almost all the molecular clouds. Second, the width of the lognormal distribution tended to decrease with an increasing mean density of the structures. These correlations suggest that the shape of the N-PDF reflects the relationship between the density and turbulent structure of the whole molecular cloud but is less affected by star-forming activities.

Funder

National Astronomical Observatory of Japan

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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