arXiv subjects

Yuxin Lin

Publications and source records attributed to Yuxin Lin.

57 records · Page 4Linked to original sources

arXiv2018

Extreme fragmentation and complex kinematics at the center of the L1287 cloud

The filamentary infrared dark cloud L1287 is actively forming a dense cluster of low-mass YSOs at its inner $\sim$0.1 pc region. To help understand the origin of this low-mass YSO cluster, the present work aims at resolving the gas structures and kinematics. We have performed $\sim$1$"$ angular resolution ($\sim$930 AU) SMA observations at $\sim$1.3 mm. From a $\sim$2$"$ resolution 1.3 mm continuum image we identified six dense cores, namely SMA1-6 with masses in the range of $\sim0.4-4$ M$_\odot$. From a $\sim$1$"$ resolution 1.3 mm continuum image, we find a high fragmentation level, with 14 compact millimeter sources within 0.1 pc (two of them associated with the known accretion outburst YSOs RNO 1C and RNO 1B). The dense gas tracer DCN (3--2) traces well the dust continuum emission and shows a clear velocity gradient along the NW-SE direction centered at SMA3. There is another velocity gradient with opposite direction around the most luminous YSO IRAS 00338+6312. The fragmentation within 0.1 pc in L1287 is very high compared to other regions at the same spatial scales. The incoherent motions of dense gas flows are sometimes interpreted by being influenced by (proto)stellar feedback (e.g., outflows), which is not yet ruled out in this particular target source. The directions of the velocity gradients traced by DCN are approximately perpendicular to those of the dominant CO outflow(s). Therefore, we alternatively hypothesize that the velocity gradients revealed by DCN trace the convergence from the $\gtrsim$0.1 pc scales infalling motion towards the rotational motions around the more compact ($\sim0.02$ pc) sources. This global molecular gas converging flow may feed the formation of the dense low-mass YSO cluster. IRAS 00338+6312 is the most likely powering source of the dominant CO outflow. A compact blue-shifted outflow from RNO 1C is also identified.

astro-ph.SR↗

arXiv2017

Cloud structure of three Galactic infrared dark star-forming regions from combining ground and space based bolometric observations

We have modified the iterative procedure introduced by Lin et al. (2016), to systematically combine the submm images taken from ground based (e.g., CSO, JCMT, APEX) and space (e.g., Herschel, Planck) telescopes. We applied the updated procedure to observations of three well studied Infrared Dark Clouds (IRDCs): G11.11-0.12, G14.225-0.506 and G28.34+0.06, and then performed single-component, modified black-body fits to derive $\sim$10$"$ resolution dust temperature and column density maps. The derived column density maps show that these three IRDCs exhibit complex filamentary structures embedding with rich clumps/cores. We compared the column density probability distribution functions (N-PDFs) and two-point correlation (2PT) functions of the column density field between these IRDCs with several OB cluster-forming regions. Based on the observed correlation and measurements, and complementary hydrodynamical simulations for a 10$^{4}$ $\rm M_{\odot}$ molecular cloud, we hypothesize that cloud evolution can be better characterized by the evolution of the (column) density distribution function and the relative power of dense structures as a function of spatial scales, rather than merely based on the presence of star-forming activity. Based on the small analyzed sample, we propose four evolutionary stages, namely: {\it cloud integration, stellar assembly, cloud pre-dispersal and dispersed-cloud.} The initial {\it cloud integration} stage and the final {\it dispersed cloud} stage may be distinguished from the two intermediate stages by a steeper than $-$4 power-law index of the N-PDF. The {\it cloud integration} stage and the subsequent {\it stellar assembly} stage are further distinguished from each other by the larger luminosity-to-mass ratio ($>$40 $\rm L_{\odot}/M_{\odot}$) of the latter.

astro-ph.GA↗

arXiv2016

Cloud Structure of Galactic OB Cluster Forming Regions from Combining Ground and Space Based Bolometric Observations

We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground based (CSO, JCMT, APEX, IRAM-30m) and space telescopes (Herschel, Planck). For the seven luminous ($L$$>$10$^{6}$ $L_{\odot}$) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, G10.3-0.1, we have performed single-component, modified black-body fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The $\sim$10$"$ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3-kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed $\sim$10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (i.e., the enclosed mass profile, the column density probability distribution function, the two-point correlation function of column density, and the probability distribution function of clump/core separations).

astro-ph.GA↗