High­resolution observations toward G191.51­0.76
S. Zahorecz , I. Jimenez­Serra , L. Testi , K. Wang , T. Onishi
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1.

Department of Physical Science, Graduate School of Science, Osaka Prefecture University
2.
National Astronomical Observatory of Japan3.
School of Physics and Astronomy, Queen Mary University of London
4.
European Southern Observatory

Abstract:Herschel and Planck, which operated in the far­IR and sub­mm, could detect cold, dense clouds in emission throughout the Galaxy.
This offered the opportunity to search for star forming clumps in the outer Galaxy and to investigate whether their physical structure,fragmentation, star formation efficiency, and gas dynamics are similar to those found in the Inner Galaxy. G191.51­0.76 is a cold coredetected with Planck in the outer Galaxy. It has a network of filaments converging into a central massive clump (hub­filament system),and it does not show 70 micron sources making it a precursor of previously reported hub­filament systems such as IRDC SDC13. We
observed the continuum and HNC, 13CS and N2H+ and HNC (1­0) emission toward G191.51­0.76 with ALMA Band 3 to determine its
physical properties, fragmentation and gas dynamics. We identified two main dense fragments, corresponding to the Herschel clumps.
They show different evolutionary stages based on their chemical properties. Future deuteration studies will help us to better
understand their chemical age and evolution.

The target of this study is PLCKECC G191.51­00.76. We have selected this source from the Planck Early Cold Cores (ECC,Planck Collaboration 2015) catalogue focusing on the objects detected in emission in the outer Galaxy (within the third and fourthquadrants) and which were observed within the Herschel Hi­GAL project. Its T dustis <15K, and it does not show strong evidence foralready formed stars (in the form of 70 um point sources). It is located in the galactic anti­center direction. It is associated to theLynds Dark Clouds at 400pc (Wang et al. 2017).
Fig. 1. Left) 250 um image of G191.51­0.76 as seen withHerschel Hi­GAL. Black asterisks indicate the 70 um sourcesin the area. Middle) Zoom­in figure of the dust temperature
image of the cloud with the ALMA observed area in Band 3.
Right) Herschel SPIRE based column density image of theobserved region. Black contours show the N1~2.85x1021 andN2~4.57x1021 cm­2 column density levels (Zahorecz et al.
2016).

APEX and ALMA observations: As part of the ESO E­093.C­

0866A project, we observed the 13CO and C18O (2­1) and N2H+ (3­2)
transitions toward G191.51­0.76 with the APEX SHFI instrument.
The region was observed with ALMA in Band 3 as project2013.1.00584.S.
The spectral setup observed high­density gas tracers, see in theTable.
Sensitivity of ~0.1mJy per 3.033''x2.095'' beam (with a positionalangle of 67°) was achieved in continuum for the combined 12m and7m array data, no emission wasdetected.
detected For the spectral lines, wecombined the calibrated visibilities
from the 7m and 12m array forimaging. We used the CASA
feather task to combine theinterferometric and single dish TP
observations. Images of the line
emission with a 10'' beam werecreated and used in this study. A
sensitivity of ~10mJy/beam wasachieved for the line observations for 0.23km/s bandwidth.

CO (2­1), C18O (2­1), N2H+ (3­2), 13CS (2­1) and HNC(1­0) emission was detected toward G191.51­0.76 withAPEX and ALMA.
13We identified 4 cores: N1, N2, N3 and S. The FWHM valuesof the HNC line for them are 0.43 km/s, 0.43 km/s, 0.39km/s and 0.85 km/s, respectively. Their Virial­masses are:1.4, 1.6, 2.7 and 5.9 solar mass, respectively.

HNC spectra (top) for thecores and channel maps
(right).
S core is the most evolved(no 13CS and strong N2H+),N1 is the youngest.

References and acknowledgement:Planck Collaboration, 2015, A&A, 594, 28; Wang et al. 2017, ApJS, 230, 5; Zahorecz et al. 2016, A&A, 591, 105
This work was supported by NAOJ ALMA Scientific Research Grant Number 2016­03B. I.J.­S. acknowledges the financial support received from the STFC through an Ernest Rutherford
Fellowship (proposal number ST/L004801).