Thermal Feedback in the High-mass Star- and Cluster-forming Region W51

Abstract

Thermal Feedback in the High-mass Star-and Cluster-forming Region W51http://researchonline.ljmu.ac.uk/7346/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LJMU Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain.The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription. LJMU Research OnlineThermal Feedback in the High-mass Star-and Cluster-forming Region W51 Abstract High-mass stars have generally been assumed to accrete most of their mass while already contracted onto the main sequence, but this hypothesis has not been observationally tested. We present ALMA observations of a3 1.5 pc area in the W51 high-mass star-forming complex. We identify dust continuum sources and measure the gas and dust temperature through both rotational diagram modeling of CHO H 3 and brightness-temperature-based limits. The observed region contains three high-mass YSOs that appear to be at the earliest stages of their formation, with no signs of ionizing radiation from their central sources. The data reveal high gas and dust temperatures ( > T 100 K) extending out to about 5000 au from each of these sources. There are no clear signs of disks or rotating structures down to our 1000 au resolution. The extended warm gas provides evidence that, during the process of forming, these high-mass stars heat a large volume and correspondingly large mass of gas in their surroundings, inhibiting fragmentation and therefore keeping a large reservoir available to feed from. By contrast, the more mature massive stars that illuminate compact H II regions have little effect on their surrounding dense gas, suggesting that these main-sequence stars have completed most or all of their accretion. The high luminosity of the massive protostars ( > L 10 4  L ), combined with a lack of centimeter continuum emission from these sources, implies that they are not on the main sequence while they accrete the majority of their mass; instead, they may be bloated and cool.

A Centimeter-wave Study of Methanol and Ammonia Isotopologues in Sgr B2(N): Physical and Chemical Differentiation between Two Hot Cores

“…As an older hot core, N1 has also likely spent time in stage 3, allowing efficient gas phase chemistry to proceed in dense, warm material, leading to its observed rich chemical diversity; though perhaps not enough time for the [NH 2 D/ 14 NH 3 ] ratio to fully equilibrate. As further support for an extended heating history, we see an extended halo of highly-abundant CH 3 OH in N1 that is similar to those seen in W51 (Ginsburg et al 2017), which have been attributed to internal heating rather than shocks.…”

Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde

“…The para-H 2 CO 3 22 -2 21 and 3 21 -2 20 transitions have similar upper state energies above the ground state, E u ≃ 68 K, similar spatial distributions (see Figure 2), similar line profiles (brightness temperature, linewidth, and velocity in our observations; see Figure C.1; also see Tang et al 2017a,b,c), and are often detected together in molecular clouds (e.g., Bergman et al 2011;Wang et al 2012;Lindberg & Jørgensen 2012;Ao et al 2013;Immer et al 2014;Treviño-Morales et al 2014;Ginsburg et al 2016Ginsburg et al , 2017Tang et al 2017a,b,c;Lu et al 2017). The CH 3 OH 4 22 -3 12 transition at 218.440 GHz is well separated from the para-H 2 CO (3 22 -2 21 ) transition in the OMC-1 region (see Figures 1 and C.1).…”

Feedback from OB stars on their parent cloud: gas exhaustion rather than gas ejection

“…It is these clumps that will form the next generation of stars therefore, with an average density and free-fall time of 2.46×10 5 cm −3 , 0.06 Myr respectively, the SFR ff for this second generation of clumps is ∼ 64.3 × 10 −3 M yr −1 showing that the total clump mass and SFR ff are 3.4 and 8 times larger than in the quiescent region. As shown by Ginsburg et al (2017) in the W51 region, it is very likely that the change in these clump properties is the result of stellar feedback via increased gas temperature and local gas compression (see clumps #1 and #3 in Fig. 4).…”