Abstract
Stars are born in dense cores of molecular clouds. The core mass function (CMF), which is the mass distribution of dense cores, is important for understanding the stellar initial mass function (IMF). We obtained 350 μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory (CSO) telescope. A 350 μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9″, corresponding to 1.2 × 103 AU at the distance of the Ophiuchus molecular cloud (131 pc). The data was reduced using the Comprehensive Reduction Utility for SHARC-II (CRUSH). The flux density map was analyzed using the GaussClumps algorithm, within which 75 cores has been identified. We used the Spitzer c2d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores (a subcategory of starless cores) were also identified. The excitation temperatures, which were derived from FCRAO 12CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with µ = −1.18 ± 0.10, σ = 0.58 ± 0.05 and µ = 1.40 ± 0.10, σ = 0.50 ± 0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.
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References
Ward-Thompson D, Scott P F, HILLS R E, et al. A submillimetre continuum survey of pre protostellar cores. Mon Not R Astron Soc, 1994, 268: 276–290
Kirk J M, Ward-Thompson D, André P. The initial conditions of isolated star formation-VI. SCUBA mapping of pre-stellar cores. Mon Not R Astron Soc, 2005, 360: 1506–1526
Ward-Thompson D, Andre P, Crutcher R, et al. Protostars and Planets V. Reipurth B, Jewitt D, Keil K, eds. Tucson, Arizona: The University of Arizona Press, 2007
Alves J, Lombardi M, Lada C J. The mass function of dense molecular cores and the origin of the IMF. Astron Astrophys, 2007, 462: L17–L21
Lada C J, Muench A A, Rathborne J, et al. The nature of the dense core population in the pipe Nebula: Thermal cores under pressure. Astrophys J, 2008, 672: 410–422
Evans II N J, Dunham M M, Jφrgensen J K, et al. The Spitzer c2d Legacy results: Star-formation rates and efficiencies; evolution and lifetimes. Astrophys J Suppl, 2009, 181: 321–350
Tafalla M. Molecules in outflows from young Stellar objects. Astron Soc Pac, 2013, 476: 177
Tafalla M, Hacar A. HH 114 MMS: A new chemically active outflow. Astron Astrophys. 2013, 552: L9
Tafalla M, Liseau R, Nisini B, et al. High-pressure, low-abundance water in bipolar outflows. Results from a Herschel-WISH survey. Astron Astrophys. 2013, 551: A116
Enoch M, Evans II N, Sargent A, et al. The mass distribution and lifetime of Prestellar cores in Perseus, Serpens, and Ophiuchus. Astrophys J, 2008, 684: 1240–1259
Ballesteros-Paredes J, Gazol A, Kim J, et al. The mass spectra of cores in turbulent molecular clouds and implications for the initial mass function. Astrophys J, 2006, 637: 384–391
Padoan P, Nordlund Å. The Stellar initial mass function from turbulent fragmentation. Astrophys J, 2002, 576: 870–879
Larson R B. Dynamical models for the formation and evolution of spherical galaxies. Mon Not R Astron Soc, 1974, 166: 585–616
Adams F C, Fatuzzo M. A theory of the initial mass function for star formation in molecular clouds. Astrophys J, 1996, 464: 256–271
Swift J J, Beaumont C N. Discerning the form of the dense core mass function. Publ Astron Soc Pac, 2010, 122: 224–230
Li D, Velusamy T, Goldsmith P, et al. Massive quiescent cores in orion. II. Core mass function. Astrophys J, 2007, 655: 351–363
Casassus S, Dickinson C, Cleary K, et al. Centimetre-wave continuum radiation from the Ophiuchi molecular cloud. Mon Not R Astron Soc, 2008, 391: 1075–1090
Motte F, Andre P, Neri R. The initial conditions of star formation in the ρ Ophiuchi main cloud: Wide-field millimeter continuum mapping. Astron Astrophys, 1998, 336: 150–172
Johnstone D, Wilson C, Moriarty-Schieven G, et al. Large-area mapping at 850 microns. II. Analysis of the clump distribution in the ρ Ophiuchi molecular cloud. Astrophys J, 2000, 545: 327–339
Young K E, Enoch M L, Evans N J, et al. Bolocam survey for 1.1 mm dust continuum emission in the c2d legacy clouds. II. Ophiuchus. Astrophys J, 2006, 644: 326–343
Stanke T, Smith M, Gredel R, et al. An unbiased search for the signatures of protostars in the Ophiuchi molecular cloud. II. Millimetre continuum observations. Astron Astrophys, 2006, 447: 609–622
Pilbratt G L, Riedinger J R, Passvogel T, et al. Herschel space observatory. An ESA facility for far-infrared and submillimetre astronomy. Astron Astrophys, 2010, 518
Dowell C D, Allen C A, Babu R S, et al. SHARC II: A caltech submillimeter observatory facility camera with 384 pixels. Proc SPIE, 2003, 4855: 73–87
Kovács A. Scanning strategies for imaging arrays. Proc Int Soc Opt Photon, 2008, 7020: 702007
Kovács A. CRUSH: Fast and scalable data reduction for imaging arrays. Int Soc Opt Photon, 2008, 7020: 70201S
Berry D, Currie M, Jenness T, et al. Starlink 2012: The Kapuahi release. Astron Soc Pac, 2013, 475: 247–250
Stutzki J, Guesten R. High spatial resolution isotopic CO and CS observations of M17 SW-The clumpy structure of the molecular cloud core. Astrophys J, 1990, 356: 513–533
Lombardi M, Bertin G. Boyle’s law and gravitational instability. Astron Astrophys. 2001, 375: 1091–1099
Goldsmith P F. Molecular depletion and thermal balance in dark cloud cores. Astrophys J. 2001, 557: 736–746
Qian L, Li D, Goldsmith P. 13CO cores in the Taurus molecular cloud. Astrophys J, 2012, 760: 147–160
Bontemps S, André P, Kaas A A, et al. ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster. Astron Astrophys, 2001, 372: 173–194
Mamajek E E. On the distance to the Ophiuchus star-forming region. Astron Nachr, 2008, 329: 10
Ossenkopf V, Henning T. Dust opacities for protostellar cores. Astron Astrophys, 1994, 291: 943–959
Jφrgensen J K, Johnstone D, Kirk H, et al. Current star formation in the perseus molecular cloud: Constraints from unbiased submillimeter and mid-infrared surveys. Astrophys J, 2007, 656: 293–305
Enoch M L, Evans II N J, Sargent A I, et al. Properties of the youngest protostars in Perseus, Serpens, and Ophiuchus. Astrophys J, 2009, 692: 973–997
Evans, Harvey M M, Huard T L, et al. Final delivery of data from the c2d legacy project: IRAC and MIPS. Pasadena, CA: SSC, 2007
Lomax O D. Simulations of Star Formation in Ophiuchus. Dissertation for the Doctoral Degree. Wales, UK: Cardiff University, 2013
Sadavoy S I, Di Francesco J, Johnstone D. ”Starless” Super-Jeans cores in four gould belt clouds. Astrophys J, 2010, 718: L32–L37
Scalo J. Fifty years of IMF variation: The intermediate-mass stars. Astrophys Space Sci Library, 2005, 327: 23–40
Salpeter E E. The luminosity function and stellar evolution. Astrophys J, 1955, 121: 161–167
Miller G, Scalo J. The initial mass function and stellar birthrate in the solar neighborhood. Astrophys J Suppl Ser, 1979, 41: 513–547
Kroupa P. On the variation of the initial mass function. Mon Not R Astron Soc, 2001, 322: 231–246
Chabrier G. Galactic stellar and substellar initial mass function. Publ Astron Soc Pac, 2003, 115: 763–795
Olmi L, Anglés-Alcázar D, Elia D, et al. On the shape of the massfunction of dense clumps in the Hi-GAL fields. I. Spectral energy distribution determination and global properties of the mass-functions. Astron Astrophys, 2013, 551: A111
Clark P C, Klessen R S, Bonnell I A. Clump lifetimes and the initial mass function. Mon Not R Astron Soc, 2007, 379: 57–62
McKee C F, Offner S S R. The protostellar mass function. Astrophys J, 2010, 716: 167–180
Ballesteros-Paredes J, Klessen R S. Molecular cloud turbulence and star formation. Protostars and Planets V. Reipurth B, Jewitt D, Keil K, eds. Tucson, Arizona: The University of Arizona Press, 2007
McKee C, Ostriker, E. Theory of star formation. Annu Rev Astron Astrophys, 2012, 45: 565–687
Joos M, Hennebelle P, Ciardi A, et al. The influence of turbulence during magnetized core collapse and its consequences on low-mass star formation. Astron Astrophys, 2013, 554: A17
Chabrier G, Hennebelle P. Dimensional argument for the impact of turbulent support on the stellar initial mass function. Astron Astrophys, 2011, 534: A106
Federrath C, Klessen R S. The star formation rate of turbulent magnetized clouds: comparing theory, simulations, and observations. Astrophys J, 2012, 761: 156
Vázquez-Semadeni E. Hierarchical structure in nearly pressureless flows as a consequence of self-similar statistics. Astrophys J, 1994, 423: 681–692
Klessen R S. The formation of stellar clusters: Mass spectra from turbulent molecular cloud fragmentation. Astrophys J, 2001, 556: 837–846
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Zhang, G., Li, D., Hyde, A.K. et al. 350 μm map of the Ophiuchus molecular cloud: core mass function. Sci. China Phys. Mech. Astron. 58, 1–11 (2015). https://doi.org/10.1007/s11433-014-5561-7
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DOI: https://doi.org/10.1007/s11433-014-5561-7