A Hunt for Massive Starless Cores

Abstract

We carry out an ALMA N 2 D + (3-2) and 1.3 mm continuum survey towards 32 high mass surface density regions in seven Infrared Dark Clouds with the aim of finding massive starless cores, which may be the initial conditions for the formation of massive stars. Cores showing strong N 2 D + (3-2) emission are expected to be highly deuterated and indicative of early, potentially pre-stellar stages of star formation. We also present maps of these regions in ancillary line tracers, including C 18 O(2-1), DCN(3-2) and DCO + (3-2). Over 100 N 2 D + cores are identified with our newly developed corefinding algorithm based on connected structures in position-velocity space. The most massive core has ∼ 70 M (potentially ∼ 170 M ) and so may be representative of the initial conditions or early stages of massive star formation. The existence and dynamical properties of such cores constrain massive star formation theories. We measure the line widths and thus velocity dispersion of six of the cores with strongest N 2 D + (3-2) line emission, finding results that are generally consistent with virial equilibrium of pressure confined cores.

GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation

“…Stars are formed within a cell only if they have been refined to the finest level of resolution and the density exceeds a particular threshold value, n H,sf . The fiducial star formation density threshold is chosen to be n H,sf =10 6 cm −3 , which is set partly based on observed densities of pre-stellar cores (e.g., Kong et al 2017). We will consider variation of this parameter by a factor of two to higher and lower values.…”

High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

“…Starless clumps are the objects that fragment into dense starless cores (r 0.15 < pc), which subsequently contract to form individual or bound systems of protostars (Tan et al 2014). Despite many searches, there are only a few candidate high-mass starless cores known to date (e.g., Wang et al 2011Wang et al , 2014Tan et al 2013;Cyganowski et al 2014;Kong et al 2017). Recently, one of the most promising candidates, G028.37+00.07 (C1), was removed from the list because ALMA and NOEMA observations reveal protostellar outflows driven by the core (Feng et al 2016;Tan et al 2016).…”

Sulphur-bearing and complex organic molecules in an infrared cold core

“…These regions could become the birth place of massive stars (de Wit et al 2005;Battersby et al 2014). Temperatures inside such clouds are of only a few kelvins and densities are around 10 5 cm −3 , with masses of ≈ 50 M ⊙ (Butler & Tan 2009, 2012Kong et al 2017Kong et al , 2018. Cold core sources display a rich and complex chemistry, revealed by the detection of many molecular species that provide important clues about the early stages of stellar evolution (Caselli & Ceccarelli 2012).…”

“…Besides the ⋆ E-mail: pedro.beaklini@iag.usp.br low temperature, outflows in dark regions have been already detected in these sources through observations of ALMA (Atacama Large Millimeter Array), NOEMA (North Extended Millimeter Array), and SMA (Submillimeter Array) (Tan et al 2016;Feng et al 2016;Pillai et al 2019). Normally, the molecule N 2 D + is used as a main tracer of temperature and density of these cold cores (Crapsi et al 2005;Tan et al 2013;Kong et al 2017).…”

“…In the present work, we use the ALMA observations of a sample of infrared dark clouds obtained by Kong et al (2017) to search for new molecular line emission and study the chemistry in starless cold cores. Is it possible to detect sulphur-bearing molecules and carbon molecular complex species in these cores?…”