Molecular Clouds Associated with HⅡRegions and Candidates within l=106°.65 to 109°.50 and b=-1°.85 to 0°.95

We present a large-scale simultaneous survey of the CO isotopologues(^(12)CO,^(13)CO,and C^(18)O)J=1-0 line emission toward the Galactic plane region of l=106°.65 to 109°.50 and b=-1°.85 to 0°.95 using the Purple Mountain Observatory 13.7 m millimeter-wavelength telescope.Except for the molecular gas in the solar neighborhood,the emission from the molecular gas in this region is concentrated in the velocity range of[-60,-35]km s^(-1).The gas in the region can be divided into four clouds,with mass in the range of~10^(3)-10^(4)M☉.We have identified 25 filaments based on the^(13)CO data.The median excitation temperature,length,line mass,line width,and virial parameter of the filaments are 10.89 K,8.49 pc,146.11 M☉pc^(-1),1.01 km s^(-1),and 3.14,respectively.Among these filaments,eight have virial parameters of less than 2,suggesting that they are gravitationally bound and can lead to star formation.Nineteen HⅡregions or candidates have previously been found in the region and we investigate the relationships between these HⅡregions/candidates and surrounding molecular clouds in detail.Using morphology similarity and radial velocity consistency between HⅡregions/candidates and molecular clouds as evidence for association,and raised temperature and velocity broadening as signatures of interaction,we propose that 12 HⅡregions/candidates are associated with their surrounding molecular clouds.In the case of the HⅡregion of S142,the energy of the HⅡregion is sufficient to maintain the turbulence in the surrounding molecular gas.

106 New Emission-line Galaxies and 29 New Galactic HⅡ Regions are Identified with Spectra in the Unknown Data Set of LAMOST DR7

This work is to retrieve emission-line spectra from the“Unknown”data set in LAMOST DR7 V1.2,most of which are low signal-to-noise ratios spectra.In the work,we perform emission line search and redshift calculations on the Unknown data set to get possible emission line galaxy spectra.Taking the galaxy spectra released by LAMOST as templates,the Product Quantization(PQ)based approximate nearest neighbor(ANN)search is used to retrieve the nearest neighbors of each spectrum.We keep the spectra for which the calculated redshift and the published redshift of the template meet the threshold,and 16,188 spectra with emission lines are obtained from the LAMOST DR7 Unknown data set.After visual inspection of spectra 10,266 spectra are left,in which 5828 spectra are identified as emission-line galaxies,1782 spectra show ionization nebula features,and other 2656 are not clearly classified.Among 5828 spectra,5720 can be found in Strasbourg astronomical Data Center catalog,Sloan Digital Sky Survey catalog,or NASA/IPAC Extragalactic Database catalog.The 108 spectra(corresponding to 106unique coordinates of R.A.and decl.)which have no record in these three databases are new discoveries;for the1782 spectra showing ionization nebula features,most of them have radial velocities less than 150 kilometers per second.We check them with the latest version of WISE HⅡcatalog V2.0(short for HIICat V2)and 985 out of the1782 spectra belong to 72 HⅡregions.Of these HⅡregions,43 were previously identified while the other 29 are newly identified in this work including 797 newly observed spectra.Besides,there are still 2656 spectra that cannot be clearly classified although they have obvious emission lines and with small redshift.Finally,106 new emissionline galaxies and 29 new Galactic HⅡregions are identified,and we conclude that the ANN method sped up by the PQ algorithm is efficient in solving the problem of pairing spectra with massive data set to figure out their classes.We present our result at the link http://paperdata.china-vo.org/LY_paper/Work2/press Work2_last.zip.

Discovery of Three Large HII Regions in the Galactic Plane

We discovered three large HⅡ regions： G148.8＋2.3, G149.5＋0.0 and G169.9＋2.0 in the Sino-German A6 cm polarization survey of the Galactic plane. They have been identified based on the flat spectral indexes and the strong infrared emission properties.

Line profile studies of hydrodynamical models of cometary compact H II regions

We simulate the evolution of cometary H II regions based on several champagne flow models and bow shock models, and calculate the profiles of the [Ne II] fine-structure line at 12.81 μm, the H30α recombination line and the [Ne III] finestructure line at 15.55 μm for these models at different inclinations of 0°, 30° and 60°. We find that the profiles in the bow shock models are generally different from those in the champagne flow models, but the profiles in the bow shock models with lower stellar velocity （≤ 5 km s^-1） are similar to those in the champagne flow models. In champagne flow models, both the velocity of peak flux and the flux weighted central velocities of all three lines point outward from molecular clouds. In bow shock models, the directions of these velocities depend on the speed of stars. The central velocities of these lines are consistent with the stellar motion in the high stellar speed cases, but they are opposite directions from the stellar motion in the low speed cases. We notice that the line profiles from the slit along the symmetrical axis of the projected 2D image of these models are useful for distinguishing bow shock models from champagne flow models. It is also confirmed by the calculation that the flux weighted central velocity and the line luminosity of the [Ne III] line can be estimated from the [Ne II] line and the H30α line.

Model of Hydrogen Deficient Nebulae in H II Regions at High Temperature

In current photoionization models, determination of the ionization structure of the nebulae is a crucial part of the calculations for non-uniform hydrogen density. We have been tried to compute temperature fluctuations of electron and electron density by changing hydrogen density by scale factor of 10 at high temperature of blackbody. We have studied the ionization structure of hydrogen and helium by means of cloudy C13.01 codes. We find a reasonable close agreement of the computed value. Moreover, the ionization structure of oxygen at ionization stages of, O I - O IV, in gaseous nebulae are studied by changing non uniform hydrogen density with power law. Our simulation also shows that how the change of this density affect temperature fluctuations, electron density and ionization structures of oxygen, helium and hydrogen with and without grains. The result also shows the impact of the forbidden lines of [O III] and [O II] to cool down the temperature of electron.

Multi-wavelength study of triggered star formation around 25 H II regions

We investigate 25 H II regions that show bubble morphology in 13CO（1-0） and infrared data, to search for quantitative evidence of triggered star formation by processes described by the collect and collapse （CC） and radiatively driven implosion （RDI） models. These H II regions display the morphology of a complete or partial bubble at 8 μm, and are all associated with the molecular clouds that surround them. We found that the electron temperature ranges from 5627 K to 6839 K in these H II regions, and the average electron temperature is 6083 K. The age of these H II regions is from 3.0× 10^5 yr to 1.7 × 10^6 yr, and the mean age is 7.7 × 10^5 yr. Based on the mor- phology of the associated molecular clouds, we divide these H II regions into three groups, which may support CC and RDI models. We select 23 young IRAS sources which have an infrared luminosity of 〉 10^3 Lo in 19 H II regions. In addition, we iden- tify some young stellar objects （including Class I sources）, which are only concen- trated in H II regions G29.007＋0.076, G44.339-0.827 and G47.028＋0.232. The poly- cyclic aromatic hydrocarbon emissions of the three H II regions all show a cometary globule. Comparing the age of each H II region with the characteristic timescales for star formation, we suggest that the three H II regions can trigger clustered star forma- tion by an RDI process. In addition, we detect seven molecular outflows in the five H II regions for the first time. These outflow sources may be triggered by the corresponding H II regions.

Investigation of star formation toward the Sharpless 155 H II region

We present a comprehensive study of star formation toward the H II re- gion Sharpless 155 （$155）. Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared. The surface density distri- bution of selected 2MASS sources toward S 155 indicates the existence of a compact cluster, which is spatially consistent with the position of the exciting source of the Htt region, HD 217086. A sample of more than 200 sources with excessive emission in the infrared were selected based on their 2MASS color indices. The spatial distri- bution of the sample sources reveals the existence of three young subclusters in this region, among which subcluster A is spatially coincident with the bright rim of the H II region. In addition, photometric data from the WISE survey were used to identify and classify young stellar objects （YSOs）. To further explore the evolutionary stages of the candidate YSOs, we fit the spectral energy distributions of 44 sources, which led to the identification of 14 Class I, 27 Class II and 3 Class Ⅲ YSOs. The spatial distribu- tion of the classified YSOs at different evolutionary stages presents a spatiotemporal gradient, which is consistent with a scenario of sequential star formation. On the other hand, Herschel PACS observations toward the interface between S 155 and the ambi- ent molecular cloud disclose an arc-shaped dust layer, the origin of which could be attributed to the UV dissipation from early type stars, e.g. HD 217061, in S155. Four dusty cores were revealed by the Herschel data, which hints at new generations of star formation.

彗状致密HⅡ区的动力学模拟研究进展

研究表明,在新形成大质量恒星辐射的影响下,分子云中会形成高密度的HⅡ区。近年来观测到一些非球对称彗星状致密HⅡ区,学者们为了解释这类目标的产生,先后建立了一系列HⅡ区动力学模型。这些工作有利于进一步认识致密HⅡ区的形成和演化及大质量恒星的形成。这里介绍了彗星状致密HⅡ区的模型模拟和计算方法方面的研究进展,阐述了香槟流和弓形激波两种解释模型的异同,以及该领域未来的发展方向。

Probing star formation and feedback using CCOSMA and archival data in the CFG028.68–0.28 quasi-sinusoidal filament

We have performed a multi-wavelength study toward a quasi-sinusoidal filament(CFG028.68–0.28). A new large-scale ^12CO J = 3-2 map was obtained from the China-Cologne Observation for Sub Millimeter Astronomy(CCOSMA) 3m radio telescope. Based on the ATLASGAL catalog, we have identified 27 dust clumps in the filament. Through the relationship between the mass and radius of these clumps, 67% of these clumps are dense and massive enough to potentially form massive stars. The obtained CFE is ~11% in the filament. The filament has a linear mass density of ~305 M⊙pc^-1, which is smaller than its critical mass to length ratio. This suggests that the external pressure from the neighboring H Ⅱ regions may help prevent the filament from dispersing under the effects of turbulence. Comparing the energy injection from outflows and H Ⅱ regions in the filament, the ionization feedback from the H Ⅱ regions can help maintain the observed turbulence.

Metallicity and star formation activities of the interacting system Arp 86 from observations with MOS on the Xinglong 2.16m telescope

We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using mulri-object spectroscopy with the 2.16 m telescope at the Xinglong Observing Station. We find that the oxygen abundance gradient in Arp 86 is flatter than that in normal disk galaxies, which confirms that gas inflows caused by tidal forces during encounters can flatten the metallicity distributions in galaxies. The companion galaxy NGC 7752 is currently experiencing a galaxy-wide starburst with a higher star for- marion rate surface density than the main galaxy NGC 7753, which can be explained in that the companion galaxy is more susceptible to the effects of interaction than the primary. We also find that the galaxy 2MASX J23470758＋2926531 has similar abun- dance and star formation properties to NGC 7753, and may be a part of the Arp 86 system.

Radio recombination line observations at 1.0-1.5 GHz with FAST

H Ⅱ regions made of gas ionized by radiations from young massive stars,are widely distributed in the Milky Way.They are tracers for star formation,and their distributions are correlated with the Galactic spiral structure.Radio recombination lines(RRLs) of hydrogen and other atoms allow for the most precise determination of physical parameters such as temperature and density.However,RRLs at around 1.4 GHz from HⅡ regions are weak and their detections are difficult.As a result,only a limited number of detections have been obtained yet.The 19-beam receiver on board of the Five-hundred-meter Aperture Spherical radio Telescope(FAST) can simultaneously cover 23 RRLs for Hnα,Henα,and Cnα(n=164-186),respectively.This,combined with its unparalleled collecting area,makes FAST the most powerful telescope to detect weak RRLs.In this pilot survey,we use FAST to observe nine HⅡ regions at L band.We allocate20 minutes pointing time for each source to achieve a sensitivity of around 9 mK in a velocity resolution of2.0 km s^(-1).In total,21 RRLs for Hnα and Cnα at 1.0-1.5 GHz have been simultaneously detected with strong emission signals.Overall,the detection rates for the H167α and C167α RRLs are 100%,while that for the He167α RRL is 33.3%.Using hydrogen and helium RRLs,we measure the electron density,electron temperature,and pressure for three HⅡ regions.This pilot survey demonstrates the capability of FAST in RRL measurements,and a statistically meaningful sample with RRL detection,through which knowledge about Galactic spiral structure and evolution can be obtained,is expected in the future.

DEFPOS Hα observations of the W80 Complex

We present Hα emission line measurements of the W80 nebula complex. A total of 26 regions have been observed inside the nebula with the Dual Etalon Fabry- Perot Optical Spectrometer system at the f/48 Coud6 focus of the 150 cm RTT150 telescope located at TUBITAK National Observatory in Antalya, Turkey. The inten- sities, local standard of rest velocities, heliocentric radial velocities and linewidths for full width at half maximum of the Hα emission lines have been determined from these observations. They lie in the range of 259 to 1159 Rayleigh （R; 1R = 106/47r pho- tons cm-2 sr-1 S-1 = 2.41 × 10-7 erg cm-2 sr-1 S-1 at Ha）, 4 to 12 km s-1, -3 to -11 km s-1 and 44 to 55 km s-i, respectively. The radial velocity measurements show that there are several maxima and minima inside W80. The new results confirm findings in the literature that the complex seems to be rather uniform in terms of radial velocity and no turbulent motion is seen inside the complex. The average value of the calculated emission measure for the region is 3.1 pc cm-6.

Detecting the intrinsic Baldwin Effect of the optical FeII complex in Luminous Seyfert 1 Galaxy Fairall 9

We analyze the optical spectra of Fairall 9,a luminous Seyfert 1 galaxy.They are obtained from the AGN Watch program that has monitored this object for 9 months.The flux and variation of the optical FeII complex is measured using multi-component profile modeling with FeⅡ templates.A convincing intrinsic Baldwin Effect(BEff) of optical FeⅡ emission blends in Fairall 9 is discovered for the first time.The variation of FeⅡ/Hβ(RFe) in Fairall 9 is obtained.We also detect a marginal anti-correla tion between RFe and the continuum flux in its spectra.This anti-correlation and the relatively broad profile of Hβ in this galaxy support the dichotomy reported by Wang et al.(2005).