The Molecular Lines Of CO Isotopes Of The High Galactic Latitude Cloud HSVMT27

HSVMT27 is a molecular cloud with a central coordinate(l,b)=(153 °,37 °)in the second quadrant of the Milky Way.No in-depth study has been carried out,since it was observed by Heitahausen et al.using the CfA 1.2m telescope in 1993.In this paper,The observations of CO toward HSVMT27 were made using the Delhiha 13.7 m telescope with a coverage of 5.25 deg2.Of which from 2.84 deg2 were detected CO emissions.Compared with the previous CO survey in 1993,spatial resolution of the image is improved nearly by 10 times,and 26 13 CO dense cloud cores are certified for the first time.In addition,by analyzing the 12 CO spectra,the range of excitation temperature of the molecular cloud is from 4K to 11 K,and the whole HSVMT27 Molecular mass is about 840 M ?.A number of C18 O line were detected in the HSVMT27 during the observations.However,the C18 O emission,with the main beam temperatures lower than 0.4K,is too weak to be well mapped.No HCO+(J = 1-0)emission was detected toward the most dense molecular cloud nuclei,indicating that it is unlikely to be in a collapse state.All in all,this paper presents no evidence of star formation activity in this cold,thin molecular cloud for the present and in the future.Over the past two decades,the international community has kept passion to study the distance to the high-latitude molecular clouds.The distance to the molecular clouds in the Ursa Major where the HSVMT27 locates,is very uncertain.In the past,the distance is usually estimated by extinction or photometric methods.According to the photometric distance catalog of the high-latitude molecular clouds,d =350 pc was taken as the distance to HSVMT27.In this paper,we also discussed the impact of distance errors on results that mainly reflect the estimations of the rotation speed of the molecular cloud nucleus.The previous survey found that atomic gas and dust in HSVMT27,the former is associated with the molecular gas at the speed of view.In addition,the CO line contains a components with velocity of-47 km s-1 in HSVMT27,indicating the medium-speed molecular gas in the second quadrant of the Milky Way which locates in the Perseus arm with a scale height of about 1 kpc.However,no high-speed presence in our observations,due to the far distance.