Core fragmentation and Toomre stability analysis of W3(H2O). A case study of the IRAM NOEMA large program CORE

Abstract

Context. The fragmentation mode of high-mass molecular clumps and the properties of the central rotating structures surrounding the most luminous objects have yet to be comprehensively characterised. <BR /> Aims: We study the fragmentation and kinematics of the high-mass star-forming region W3(H<SUB>2</SUB>O), as part of the IRAM NOrthern Extended Millimeter Array (NOEMA) large programme CORE. <BR /> Methods: Using the IRAM NOEMA and the IRAM 30 m telescope, the CORE survey has obtained high-resolution observations of 20 well-known highly luminous star-forming regions in the 1.37 mm wavelength regime in both line and dust continuum emission. <BR /> Results: We present the spectral line setup of the CORE survey and a case study for W3(H<SUB>2</SUB>O). At 0.''35 (700 AU at 2.0 kpc) resolution, the W3(H<SUB>2</SUB>O) clump fragments into two cores (west and east), separated by 2300 AU. Velocity shifts of a few km s<SUP>-1</SUP> are observed in the dense-gas tracer, CH<SUB>3</SUB>CN, across both cores, consistent with rotation and perpendicular to the directions of two bipolar outflows, one emanating from each core. The kinematics of the rotating structure about W3(H<SUB>2</SUB>O) W shows signs of differential rotation of material, possibly in a disk-like object. The observed rotational signature around W3(H<SUB>2</SUB>O) E may be due to a disk-like object, an unresolved binary (or multiple) system, or a combination of both. We fit the emission of CH<SUB>3</SUB>CN (12<SUB>K</SUB>-11<SUB>K</SUB>), K = 4-6 and derive a gas temperature map with a median temperature of 165 K across W3(H<SUB>2</SUB>O). We create a Toomre Q map to study thestability of the rotating structures against gravitational instability. The rotating structures appear to be Toomre unstable close to their outer boundaries, with a possibility of further fragmentation in the differentially rotating core, W3(H<SUB>2</SUB>O) W. Rapid cooling in the Toomre unstable regions supports the fragmentation scenario. <BR /> Conclusions: Combining millimetre dust continuum and spectral line data toward the famous high-mass star-forming region W3(H<SUB>2</SUB>O), we identify core fragmentation on large scales, and indications for possible disk fragmentation on smaller spatial scales. <P />Based on observations from an IRAM large program. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Observational data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A46">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A46</A>, or alternatively at <A href="http://www.mpia.de/core">http://www.mpia.de/core</A>.