Infall and outflow motions in the high-mass star forming complex G9.62+0.19
Tie Liu, Yuefang Wu, Sheng-Yuan Liu, Sheng-Li Qin, Yu-Nung Su, Huei-Ru Chen, Zhiyuan Ren
aa r X i v : . [ a s t r o - ph . S R ] J a n Infall and outflow motions in the high-mass star forming complexG9.62 + Tie Liu , Yuefang Wu , Sheng-Yuan Liu , Sheng-Li Qin , , Yu-Nung Su , Huei-Ru Chen , andZhiyuan Ren Received ; acceptedAccepted to ApJ Department of Astronomy, Peking University, 100871, Beijing China; [email protected],[email protected] Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan I. Physikalisches Institut, Universit¨at zu K¨oln, Z¨ulpicher Str. 77, 50937 K¨oln, Germany National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu,Taiwan 2 –
ABSTRACT
We present the results of a high resolution study with the Submillimeter Arraytowards the massive star forming complex G9.62 + ⊙ for the northern, middle andsouthern dust cores, respectively. Infall motions are found with HCN (4-3) and CS(7-6) lines at the middle core (G9.62 + . × − M ⊙ · yr − .In the southern core, a bipolar-outflow with a total mass about 26 M ⊙ and a mass-lossrate of 3 . × − M ⊙ · yr − is revealed in SO (8 − ) line wing emission. CS (7-6)and HCN (4-3) lines trace higher velocity gas than SO (8 − ). G9.62 + / mm cores in this region are also analyzed. The results support that UC H ii regions have a higher blue excess than their precursors. Subject headings:
Massive core:pre-main sequence-ISM: molecular-ISM: kinematics anddynamics-ISM: jets and outflows-stars: formation
1. Introduction
High-mass stars play a major role in the evolution of the Galaxy. They are the principalsources of heavy elements and UV radiation (Zinnecker & Yorke 2007). However, the formationand evolution of high-mass stars are still unclear. A possible evolution sequence of high-massstars from infrared dark clouds to classic H ii regions has been suggested (Van der Tak & Menten2005). But one of the major topics whether high-mass stars form through accretion-disk-outflow, like low-mass ones (Shu, Adams & Lizano 1987), or form via collision-coalescence(Wolfire, & Cassinelli 1987; Bonnell et al. 1998) is still far from solved.Yet more and more observations at various resolutions seem to support the accretion-disk-outflow models rather than collision-coalescence models. Disks are detected in severalhigh-mass star forming regions (Patel et al. 2005; Jiang et al. 2005; Sridharan, Williams, & Fuller2005). Outflows are found with a high detection rate as in low-mass cores in single-dishsurveys (Wu et al. 2004; Zhang et al. 2005; Qin et al. 2008a). High resolution studies havealso confirmed that molecular outflows are common in high-mass star forming regions(Su, Zhang, & Lim 2004; Qiu et al. 2007; Qin et al. 2008b,c; Qiu et al. 2009). Searchingfor inflow motions also has made large progress in recent years (Wu & Evans 2003;Fuller, Williams, & Sridharan 2005; Wyrowski et al. 2006; Klaassen, & Wilson 2007; Wu et al.2007, 2009; Furuya, Cesaroni, & Shinnaga 2011). Both infall and outflow motions in the massivecore JCMT 18354-0649S are detected (Wu et al. 2005), and further confirmed by higher resolutionobservations (Liu et al. 2011). Although accretion-disk-outflow systems are found in high-massstar forming regions, there may be di ff erences between low- and high-mass formation.The infall motion can be detected via ”blue profile”, a double-peaked profile with theblueshifted peak being stronger for optically thick lines and a single peak at the absorption part ofoptically thick lines for optically thin lines, which is caused by self absorption of the cooler outerinfalling gas towards the warmer central region (Zhou et al. 1993). In contrast, the ”red profile” 4 –where the redshifted peak of a double-peaked profile being stronger for optically thick lines issuggested as indicators for outflow motions. Mardones et al. (1997) defined the ”blue excess” in asurvey, E, as E = (N B -N R ) / N T (Mardones et al. 1997), where N T is number of sources, N B and N R mark the number of sources with blue and red profiles, respectively. The blue excess seems to beno significant di ff erences among the low-mass cores in di ff erent evolutionary phases. However,using the IRAM 30 m telescope, Wu et al. (2007) found that UC H ii regions show a higher blueexcess than their precursors, indicating fundamental di ff erences between low- and high-mass-starforming conditions. The searches need to be expanded.Located at a distance of 5.7 kpc (Hofner et al. 1994), G9.62 + ii regions, which are probably at di ff erent evolutionarystages. Multiwavelength VLA observations have identified nine radio continuum sources (denotedfrom A-I) (Garay et al. 1993; Testi et al. 2000), and components C-I are very compact ( < ′′ in diameter) (Garay et al. 1993; Testi et al. 2000). As revealed in NH (4,4), (5,5) and CH CN(J = + ii region and a dusty envelope (Hofner et al. 1996b), whileG9.62 + ii region excited by a B0.5 ZAMS star (Hofner et al. 1996b;Testi et al. 2000). Both G9.62 + + + , H O, OH, and CH OH, as well as the strong thermal NH emissionswere detected along a narrow region with projected length 20 ′′ and width ≤ ′′ (Hofner et al.1994). A possible explanation for this alignment is compression of the molecular gas by shockfront originating from an even more evolved H ii region to the west of the star-forming front(Hofner et al. 1994). High-velocity molecular outflows also have been detected in this region, 5 –and G9.62 + / gasenvironment and dynamical processes in this region, higher resolution studies at high frequenciesare needed. In this paper we report the results of the Submillimeter Array (SMA ) observationstoward G9.62 + µ m.
2. Observations
The observations of G9.62 + sys ranges from 210 to 990 K with a typicalvalue of 380 K at both sidebands during the observations. The observations had two fieldsfor the G9.62 + = h m s and DEC(J2000) = -20 ◦ ′ . ′′ , and the other wasRA(J2000) = h m s and DEC(J2000) = -20 ◦ ′ . ′′ . Uranus and Neptune wereobserved for antenna-based bandpass calibration. QSOs 1743-038 and 1911-201 were employedfor antenna-based gain correction. Neptune was used for flux-density calibration. The frequencyspacing across the spectra band was 0.8125 MHz, corresponding to a velocity resolution of ∼ − .MIRIAD was employed for calibration and imaging (Sault et al. 1995). The imaging wasdone to each field separately and the mosaic continuum map was made using a linear mosaicing Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory andthe Academia Sinica Institute of Astronomy and Astrophysics and is funded by the SmithsonianInstitution and the Academia Sinica. 6 –algorithm (task ”linmos” in MIRIAD). The 860 µ m continuum data was acquired by averagingover all the line-free channels in both sidebands. The spectral cubes were constructed usingthe continuum-subtracted spectral channels smoothed into a velocity resolution of 1 km s − .Additional self-calibration with models of the clean components from previous imaging processwas performed on the continuum data in order to remove residual errors due to phase andamplitude problems, and the gain solutions obtained from the continuum data were applied to theline data. The synthesized beam size of the continuum emission with robust weighting of 0.5 is2 . ′′ × . ′′ (P.A. = . ◦ ).
3. Results3.1. Continuum emission
The 860 µ m continuum image combining the visibility data from both sidebands is shownin Figure 1 . Three sub-mm cores are detected. The known cm and mm continuum components(Testi et al. 2000) of B, C, D, E, F, G, H, and I are marked by plus signs. Water masers(Hofner, & Churchwell 1996a) are marked by open squares and methanol masers (Norris et al.1993) by triangles. The near-IR sources (Persi et al. 2003; Testi et al. 1998; Linz et al. 2005) aremarked by filled circles. IRAC sources are taken from the database of Galactic Legacy InfraredMid-Plane Survey Extraordinaire (GLIMPSE) and labeled with asterisks. The northern core islocated at south-east of G9.62 + + µ m continuum emission at the southern core is concentrated on the hot molecular coreG9.62 + + + http: // irsa.ipac.caltech.edu / data / SPITZER / GLIMPSE / ∼ . ′′ . The southern core is foundto be elongated from north to south with an average size of 2 . ′′ , containing at least three sources,D, F, and G. F is at its peak position. The peak positions, sizes, peak intensities and total fluxesof these three sub-mm cores are listed in Column 2-5 in Table 1. The physical properties of thesecores will be further discussed in section 4.2. Tens of molecular transitions including hot molecular lines CH OH, HCOOCH , andCH OCH are detected toward both the middle and southern sub-mm cores, indicating these twocores are hot and dense (Qin et al. 2010). Figure 2 presents the full LSB and USB spectra in theUV domain over the shortest baseline. The strongest lines are identified and labeled on the plots.Only HCN (4-3) and CS (7-6) line emissions are detected towards the northern core with oursensitivity. Thus we mainly focus on the middle and southern cores in this paper. The systemicvelocities of 2.1 km s − for the middle core and 5.2 km s − for the southern core are obtainedby averaging the V lsr of multiple singly peaked lines. Six transitions of the thioformaldehyde(H CS) and molecular transitions SO (8 -7 ), CS (7-6), HC N (4-3) and HCN (4-3) are analyzedhere, while the others will be discussed in another paper. We have made gaussian fits to thebeam-averaged spectra, and present the observed parameters of these lines in Table 2.
The integrated intensity maps of four transitions of H CS towards the middle core are shownin the upper panels of Figure 3. From (a) to (d), the upper level energy of H CS transitions variesfrom ∼
90 K to ∼
400 K. The H CS emission is spatially coincident with continuum emissionof the middle core very well. The Position-Velocity (P-V) diagram and first moment map of 8 –H CS (10 , -9 , ) emission are presented in Figure 4. The P-V diagram is constructed acrossthe peak of the continuum along the N-S direction. From P-V diagram two emission peaks areclearly revealed. The velocities of the two emission peaks are at 1 and 3 km s − with 1 . ′′ spatialseparation, indicating a velocity gradient in N-S direction. The first moment map also showsvelocity changes in N-S direction. The small velocity gradient detected in H CS (10 , -9 , )emission may indicate a disk with a low inclination along the line of sight, which requires furtherconfirmation with higher angular resolution observations and other molecular line tracers.The spectra and integrated intensity maps of HC N (4-3) and SO (8 -7 ) are presented inFigure 5. The two spectra seem to be symmetric, and their cores are associated with that of thecontinuum emission very well.Figure 6 presents the spectra and P-V diagrams of HCN (4-3) and CS (7-6) emissions of themiddle core. HCN (4-3) and CS (7-6) show asymmetric profile. The blue and red emission peaksof HCN (4-3) are around 0 km s − and 6 km s − , respectively. The blueshifted emission of CS(7-6) peaks around 1 km s − , while the redshifted around 4 km s − . We can see the blueshiftedemission of both HCN (4-3) and CS (3-2) is always stronger than the redshifted emission and theabsorption is also redshifted, which are blue profiles (see Sect. 1). Besides the ”blue profile”,some weak absorption dips are found around 10 km s − in both the spectra and P-V diagrams ofHCN (4-3) and CS (7-6), and further observations are needed to determine the properties of theseabsorption dips. In this paper we only pay attention to the ”blue-profile” found in CS (7-6) andHCN (4-3) emission.The integrated intensity maps of HCN (4-3) and CS (7-6) towards the middle core arepresented in Figure 7. The HCN (4-3) and CS (7-6) are associated with the dust emission. 9 – The integrated intensity maps of four transitions of H CS at the southern core are shown inthe lower panels of Figure 3. The upper level energy of H CS transitions varies from ∼
90 K to ∼
400 K from panel (e) to panel (h). As the upper level energy increases, the emission peak of thedi ff erent transitions of H CS moves from S-E to N-W, indicating a temperature gradient in thesouthern core.Averaged spectra of SO (8 -7 ), HC N (4-3), HCN (4-3) and CS (7-6) at the southern coreare presented in Figure 8. The spectra of SO (8 -7 ) and HC N are averaged over a region of4 ′′ , while HCN (4-3) and CS (7-6) are averaged over a region of 6 ′′ . SO (8 -7 ) emission has atotal velocity extent of larger than 20 km s − . From gaussian fit to the spectrum, the peak velocityof SO emission is 5 . ± . − , coincident very well with the systemic velocity 5.2 km s − .HC N (4-3) has a velocity extent of about 15 km s − . The velocity extents of CS (7-6) and HCN(4-3) are as high as 40 km s − and 60 km s − , respectively. Emission wings are clearly detectedfrom the spectra of the four lines. A ”red-profile” is significantly exhibited in the spectra of CS(7-6) and HCN (4-3), of which the redshifted emission is always stronger than the blueshiftedemission with an absorption dip at the blueshifted side of the systemic velocity (5.2 km s − ). Thisprofile is caused by absorption of the colder blueshifted gas in front of the hot core, indicatingoutflow motions. The ”red-profile” is consistent with that detected using single dish observations(see Figure 6 of Hofner, Wiesemeyer, & Henning (2001)).The integrated intensity maps of HC N (4-3) and SO (8 -7 ) at the southern core arepresented in Figure 9. To avoid the influence of outflow motions, both the maps are integratedfrom 2 km s − to 8 km s − . Both the emission of HC N (4-3) and SO (8 -7 ) coincides with thecm / mm component F, and extends from D to G.As shown in the left panels of Figure 10, the high velocity gas of HC N (4-3) and SO (8 -7 )can be identified by the vertically dashed lines in the P-V diagrams. For SO (8 -7 ), we integrate 10 –from -4 km s − ≤ V ≤ − for the blue wing and 10 km s − ≤ V ≤
14 km s − for the red wing,and present the contour map in (c) of Figure 10. For HC N (4-3), only the red wing emission ispresented in (d) of Figure 10. The high velocity emission of both HC N (4-3) and SO (8 -7 )is associated with core F, indicating that core F is the driven source of the outflow. The blue andred wings of SO (8 -7 ) overlap to a large extent in the contour maps, and hence the molecularoutflow revealed by SO (8 -7 ) is observed close to its flow axis.Figure 11 presents the channel maps of CS (7-6) emission. The redshifted high-velocity gasseems to be elongated from north-east to south-west, while the blueshifted high-velocity gas fromnorth to south. The high velocity gas revealed by CS (7-6) is also very obvious in the P-V diagramin Figure 13(d). As shown in the P-V diagram, the blueshifted high-velocity gas extends about 8 ′′ from north to south. The high-velocity emission integrated over the wings (-12 km s − ≤ V ≤ -5km s − for the blue wing and 15 km s − ≤ V ≤
22 km s − for the red wing) is presented in Figure13(e).Figure 12 is the channel maps of HCN (4-3) emission. The maximum of absorptions appearsat around 0 km s − . The redshifted high-velocity gas seems to be elongated from west to east,while the blueshifted high-velocity gas from north to south. At very high velocity channels (V ≤ -16 km s − ), the blueshifted emission is totally located at south-east. By comparing the channelmaps and P-V diagrams (see Figure 13) of HCN (4-3) and CS (7-6) at velocity intervals -12km s − ≤ V ≤ -5 km s − and 15 km s − ≤ V ≤
22 km s − , we find similar structures in CS (7-6)and HCN (4-3) emissions. The high-velocity emission of HCN (4-3) integrated from -12 km s − to -5 km s − for the blue wing and from 15 km s − to 22 km s − for the red wing is presented inthe panel (b) of Figure 13. As of CS (7-6), the blueshifted gas revealed by HCN (4-3) is elongatedfrom north to south with the emission center located between G9.62 + + − ≤ V ≤ -13 km s − for the bluewing and 23 km s − ≤ V ≤
39 km s − for the red wing), and present the integrated emission mapin Figure 13(c). The redshifted emission is elongated from north-east to south-west with theemission center located between G9.62 + + + + -7 ), CS (7-6) and HCN (4-3) have di ff erent spatial distributions, whichshould be caused by the complicated interactions between the outflow and the ambient gas. Itmay also indicate a change of the outflow axis. The change of outflow axis is also found in IRAS20126 + -7 ), HCN (4-3) and CS (7-6) high velocity gas,it is clearly seen that G9.62 + +
4. Discussion4.1. Rotational temperature of H CS transitions
Six transitions of H CS have been detected in the middle and southern cores, enabling us toestimate the rotational temperature. Under the assumptions that the gas is optically thin underlocal thermodynamic equilibrium and the gas emission fills the beam, the rotation temperatureand beam-averaged column density can be estimated using the Rotational Temperature Diagram(RTD) by (Cummins, Linke, &Thaddeus 1986; Turner et al. 1991; Liu, et al. 2002)ln( N u g u ) = ln( N T Q rot ) − E u T rot = ln[2 . × R I ( Jy beam − ) dv ( km s − ) θ a θ b ( arcsec ) g I g K ν ( GHz ) S µ ( debye ) ] (1)where N u is the observed column density of the upper energy level, g u is the degeneracy factorin the upper energy level, N T is the total beam-averaged column density, Q rot is the rotational 12 –partition function, E u is the upper level energy in K, T rot is the rotation temperature, R I dv isthe integrated intensity of the specific transition, θ a and θ b are the FWHM beam size, g K is theK-ladder degeneracy, g I is the degeneracy due to nuclear spin, ν is the rest frequency, and S isline strength and µ the permanent dipole moment. For H CS, the interchangeable nuclei are spin , leading to ortho- and para-forms with g I equaling and , respectively (Blake et al. 1987;Turner et al. 1991). The partition function Q rot of H CS is (Blake et al. 1987) Q rot = π ( kT rot ) h ABC ] (2)where k and h are the Boltzmann and Planck constants, respectively, and A, B, and C arethe rotation constants. Thus the rotation temperature T rot and total column density N T can beestimated by least-squares fitting to the multiple transitions. We applied the RTD method towardsD, E, F, G (see Figure 14), and the fitting results are listed in the second and third columns ofTable 3. The rotational temperature of the middle core (E) is 83 ±
21 K. In the southern core, therotational temperature estimated decreases from G (91 K) to F (83 K) and D (43 K), suggestingthe temperature gradient in the southern core. The total column density of H CS ranges from1.3 × (G) to 3.8 × cm − (D).However, the filling factor and the optical depth correction were not taken account of inthe RTD method. To investigate their e ff ect we applied the Population Diagram (PD) analysis(Goldsmith, & Langer 1999; Wang et al. 2010). In the PD analysis, we haveln( ˆ N u g u ) = ln( N T Q rot ) − E u T rot + ln( f ) − ln( τ − e − τ ) (3)where ˆ N u is the inferred column density of the upper energy level from the PD analysis, f isthe source filling factor and τ is the optical depth. The optical depth τ can be expressed by(Remijan et al. 2004) τ = π S µ ν k ∆ v T rot N T Q rot e − EuTrot (4) 13 –where ∆ v is the FWHM line width. Under LTE, the upper-level populations, ˆ N u , can bepredicted according to the right-hand side of Equation (3) for a given set of total column density,N T , rotational temperature, T rot , and source filling factor, f. The expected ˆ N u were evaluated forthe parameter space of T rot = T = -10 cm − , and f between 0.01 and 1.0. Tocompare the observed N u and the inferred ˆ N u , we calculate the χ as: χ = X ( N u − ˆ N u δ N u ) (5)where δ N u is the 1 σ error of observed upper-state column density. Although the χ is agood representation of the goodness of fit, the parameter set with the lowest χ may not actuallyrepresent physical parameters very well due to the uncertainties of the observed data. In order tofind a representative parameter set, we compute a weighted mean and standard deviation for all theparameters, with the weights being the inverse of the χ . All the parameter sets where the inferredupper-level population ˆ N u corresponds with the observed upper-level population N u within 3 σ areused to compute the weighted means and standard deviations. The derived rotational temperature,total column density and filling factor of each component are list in the [3-5] columns of Table 3.The inferred optical depths of each line transition are listed in the last six columns of Table 3. Therotational temperatures of D, E, F, G are estimated to be 42 ±
34, 92 ±
74, 51 ±
23 and 105 ±
37 K,respectively. A temperature gradient in the southern core is also revealed as in the RTD method.The four components D, E, F, G has similar total column densities as high as 4 × cm − , aboutan order of magnitude higher than those obtained from RTD method, which are mainly due to thesmall source filling factor ( < CS (10 , -9 , ) at the four componentsare all much larger than one, while the other transitions are always optically thin except H CS(10 , -9 , ) line at G. 14 – In the optically thin case, the total dust and gas masses of the three sub-mm cores can beobtained with the formula M = S ν D /κ ν RB ν ( T d ) (Hildebrand 1983), where S ν is the flux at 860 µ m, D is the distance, R = κ ν is dust opacity per unit dustmass. B ν ( T d ) is the Planck function at a dust temperature of T d . We assume that T d equals therotational temperature of H CS. For the northern core, since only CS (7-6) (upper energy E u = u = d to be 50 K. Togetherwith the measurements at centimeter and millimeter wavelengths, Su et al. (2005) extrapolatedthe ionized gas emission at mm / submm wavelengths, and found that the 0.85 mm continuumassociated with components D, E, and F are dominated by thermal dust emission. They havederived opacity index β of components E and F to be 1.2, and 0.8, respectively. For the northernsub-mm core, β = . κ ν = g − for the northern, middle and southern cores, respectively (Ossenkopf & Henning1994). At the distance of 5.7 kpc , we get the total dust and gas masses for these three cores, andlist all the parameters in Table 1. The deduced masses for the northern, middle and southern coresare 13, 30, 165 M ⊙ , respectively. The column density of H are 1.2 × and 2.1 × cm − forthe middle and southern sub-mm cores, respectively. In the middle core, both CS(7-6) and HCN(4-3) emission exhibits ”blue profile” feature,indicating infall motions of the gas envelope toward the central star (Keto, Ho,& Haschick1988; Zhou et al. 1993; Zhang, Ho, & Ohashi 1998; Wu & Evans 2003; Wu et al. 2005, 2007;Fuller, Williams, & Sridharan 2005; Wyrowski 2007; Sun, & Gao 2008). The velocity di ff erence(0.9 km s − ) between the absorption dip in CS (7-6) spectrum (3 km s − ) and the systemic velocity(2.1 km s − ) is taken as the infall velocity V in . Since both HCN (4-3) and CS (7-6) emissions are 15 –not resolved towards the middle core, we simply take the dust core size as the radius of the infallregion, which may underestimate the infall rate derived below. The kinematic mass infall ratecan be calculated using dM / dt = π R in nmV in . n = × cm − is the number density of this dustcore. Taking Helium into account, the mean molecular mass m is 1.36 times of H molecule mass.The infall rate calculated is 4 . × − M ⊙ · yr − . For comparison, the V in from pure free-infallassumption is also derived with the formula V in = GM / R in . The pure free-infall velocity is V in = . − and thus the ”gravitational” mass infall rate is 1 . × − M ⊙ · yr − , which is largerthan the kinematic infall rate. Observations have suggested that there are important di ff erences in molecular abundances indi ff erent outflow regions (Bachiller et al. 1997; Choi et al. 2004; J¨orgensen, Sch¨oier, & van Dishoeck2004; Codella et al. 2005). Significant abundance enhancements are found in the shocked regionfor sulfur-bearing molecules (Bachiller et al. 1997; J¨orgensen, Sch¨oier, & van Dishoeck 2004),and the abundance of HCN in outflow regions is related to atomic carbon abundance (Choi 2002).However, previous studies of the chemical impact of outflows are confined to the well collimatedoutflows around Class 0 sources, while such studies especially high resolution studies on massiveoutflows are rare (Bachiller et al. 1997; J¨orgensen, Sch¨oier, & van Dishoeck 2004; Arce et al.2007).A red and bright IRAC source is found to be associated with the southern core. Themagnitudes of the IRAC source at 3.6 µ m, 4.5 µ m and 5.8 µ m are 10 . ± . . ± . . ± .
302 mag, respectively. The [3.6-4.5] color is as large as 1.74, indicating shockedemission in the southern core (Takami et al. 2010). Maser emissions of NH , H O, OH, and 16 –CH OH, as well as the strong thermal NH emissions also uncover the existence of the shockedgas (Hofner et al. 1994). Outflows can be revealed from shocked H emission probed by thestrong and extended emission at the 4.5 µ m band (Qiu et al. 2008; Takami et al. 2010). Thus themassive outflow in the southern core of G9.62 complex provides an ideal sample to study shockchemistry.The fractional abundance of a certain molecule is defined as χ = N T / N H , where N T is thetotal column density of a specific molecule and N H is the H column density. Assuming that thegas is optically thin and the emission fills the beam, the beam-averaged total column density of aspecific molecule can be obtained from: N T = . × R I ( Jy beam − ) dv ( km s − ) Q rot e E u / T rot θ a θ b ( arcsec ) g I g K ν ( GHz ) S µ ( debye ) (6)Assuming that T rot of HC N equals to that of H CS and the gas is optically thin, N T ofHC N is calculated to be 3 . × cm − at the core region. At the galactocentric distance of 3 kpcfor G9.62 + N] / [ N] ≈ . × cm − . Therefore, the fractional abundance of HCN relative to H at the coreregion is 5 . × − . HCN appears to be greatly enhanced in the outflow regions of the L1157(Bachiller et al. 1997), while has similar abundances in the outflow region and the ambient cloudof NGC 1333CIRAS 2A (J¨orgensen, Sch¨oier, & van Dishoeck 2004). Owing to the lack of adirect estimation of the H column density towards the outflow region, the fractional abundanceof HCN in the outflow region is also assigned to 5 . × − in calculating the outflow parameters.Since the HC N emission traces outflowing gas at much lower velocity than HCN, perhaps HCNcould be more enhanced in the high velocity component. With the possibility of higher opacityand the lack of direct H column density measurement, the derived fractional abundance perhapsis a lower limit anyway. Su et al. (2007) estimate an HCN abundance of ∼ − × − in the 17 –massive outflow lobes of IRAS 20126 + ff ers self-absorption,the abundance ratios among SO (8 − ), CS (7-6), and HCN (4-3) were inferred from thebeam-averaged spectra taken from the redshifted outflow lobe. The abundance ratio as a functionof flow velocity (the outflow velocity relative to the systemic velocity) of [CS / SO] is obtainedassuming five di ff erent excitation temperatures in the left panel of Figure 15. It can be seenthat the abundance ratio of [CS / SO] increases with the excited temperature. At each excitationtemperature, the abundance ratio of [CS / SO] has lower values at flow velocities less than 6 km s − ,and higher values when V f low larger than 8 km s − , whereas the abundance ratio seems tobe constant at flow velocities between 6 km s − and 8 km s − . There are two reasons for thelower abundance ratio when V f low < − : first, the flux missing of CS (7-6) due to theinterferometer is more serious than SO (8 − ); second, CS (7-6) may be more optically thick atlower flow velocities than SO (8 − ). As shown in the P-V diagrams, the emission region ofCS (7-6) is much larger than SO (8 − ) at high velocities. The higher abundance ratio whenV f low > − is due to the smaller filling factor of SO (8 − ) emission. We propose themean observed value between 6 km s − and 8 km s − can represent the actual abundance ratio of[CS / SO]. Assuming a typical excitation temperature of T ex =
30 K (Wu et al. 2004), the abundanceratio of [CS / SO] at the redshifted lobe is inferred as 0.7. Nilsson et al. (2000) find that the[SO / CS] abundance ratios are strongly enhanced in the Orion A and NGC 2071 outflows wherethe [SO / CS] ratios are estimated to be about 24 and 2.2, respectively. However, the [SO / CS]abundance ratio in the outflow of G9.62 + / HCN] decreases linearlywith the flow velocity. To avoid the missing flux di ffi culty, the abundance ratio is calculated athigh flow velocities larger than 7 km s − . The decreasing of the abundance ratio with velocity is 18 –because that the emission region traced by CS (7-6) is always smaller than HCN (4-3), leading tosmaller filling factor for CS (7-6), which can be verified easily by comparing the channel mapsbetween CS (7-6) in Figure 11 and HCN (4-3) in Figure 12 at high velocities. We fitted theobserved data with a linear function, and adopted the value at flow velocity of 10 km s − as theactual abundance ratio of [CS / HCN] in the outflow region, which is [CS / HCN] = . × − , the fractional abundances of CS and SO are deduced to be6 . × − and 8 . × − , respectively. − ) emission The SO (8 − ) emission in the southern core shows line wings, suggesting outflowmotions. From the integrated intensity map in Figure 10(c), we find the outflow lobes revealedby SO (8 − ) emission peak at di ff erent position with di ff erent position angle compared withpreviously reported H S (2 , − , ) (Gibb, Wyrowski, & Mundy 2004) and HCO + (1-0) data(Hofner, Wiesemeyer, & Henning 2001). But in the same sense, the blue- and red-lobes revealedby SO overlap to a large extent as well as HCO + (1-0) and H S (2 , − , ) data, consistent withthe argument of the outflow being viewed pole-on (Hofner, Wiesemeyer, & Henning 2001).The total mass of each outflow lobe is given by: M f low = . × − D Q rot e E u / T rot χν S µ Z τ − e − τ S ν dv (7)where M f low , D, S ν , χ , and τ are the outflow gas mass in M ⊙ , source distance in kpc, line fluxdensity in Jy, relative abundance to H , and optical depth. The other parameters have the sameunits as in equation (1). The fractional abundance of SO is taken as 8 . × − (see Sec.4.4.1).Assuming an excitation temperature of 30 K and the outflowing gas is optically thin, the inferredoutflow masses are 13 M ⊙ for each of red and blueshifted lobes. Thus, the momentum can becalculated by P = P M(v)dv, and the energy by E = P M(v)v dv, where v is the flow velocity. 19 –The derived parameters are listed in Table 4. The momentum and energy of the red lobe are 82M ⊙ · km s − and 5 . × erg. For the blue lobe, the momentum and energy are calculated to be86 M ⊙ · km s − and 5 . × erg. The dynamical timescale t dyn is estimated as R / V char , whereR ( ∼ char ( ∼ − ) is assumed as the mass weighted mean velocity. Thus, the dynamictimescale is estimated to be 1 × year, which may be underestimated due to the uncertaintyof the outflow scale. The mechanical luminosity L, and the mass-loss rate ˙ M are calculated asL = E / t, ˙ M = P / ( tV w ), where the wind velocity V w is assumed to be 500 km s − (Lamers et al.1995). The mechanical luminosity L and the total mass-loss rate are estimated to be 9.3 L ⊙ and3 . × − M ⊙ · yr − , respectively. The CS (7-6) emission at the southern core shows ”red-profile” with wide wings. We take6 . × − as the fractional abundance of CS relative to H along the outflow lobes. AssumingT ex =
30 K, we derive the parameters for the CS outflow (Table 4) with the same method used forSO (8 − ). The outflow masses at very high velocities (v f low >
10 km s − ) are 3.7 M ⊙ and5.5 M ⊙ for the blueshifted and redshifted lobes, respectively. The momentum and energy of theblueshifted lobe at very high velocities are calculated to be 47 M ⊙ · km s − and 6 . × erg. Forthe redshifted lobe, the momentum and energy at extremely high velocities are calculated to be 68M ⊙ · km s − and 8 . × erg, which are similar to the blueshifted lobe. As discussed before, HCN (4-3) has a velocity extent of at least 60 km s − , which tracesextremely high-velocity (EHV) gas. Adopting an excited temperature of 30 K, and an HCN-to-H
20 –abundance ratio of 5 . × − , the parameters of the outflow are calculated and listed in Table4. The outflow mass at very high velocities (v f low >
10 km s − ) are 5.2 M ⊙ and 17.6 M ⊙ forthe blueshifted and redshifted lobes, respectively. The momentum and energy of the blueshiftedlobe at very high velocities are 85 M ⊙ · km s − and 1 . × erg. For the redshifted lobe, themomentum and energy at very high velocities are 294 M ⊙ · km s − and 5 . × erg, which arelarger than the blueshifted lobe. A broken power law, dM ( v ) / dv ∝ v − γ usually exhibits in molecular outflows near youngstellar objects (Chandler et al. 1996; Lada, & Fich 1996; Ridge, & Moore 2001; Su, Zhang, & Lim2004; Qiu et al. 2007, 2009). The slope, γ , typically ranging from 1 to 3 at low outflow velocities,and often steepens at velocities larger than 10 km s − — with γ as large as 10 in some cases(Arce et al. 2007). Assuming optically thin, the mass-velocity diagrams of the outflow at thesouthern core of G9.62 + − ), CS (7-6), HCN (4-3)results were all used in the mass spectra. We calculate the outflow mass traced by CS (7-6) andHCN (4-3) from V f low of 10 km s − to avoid the absorption of the spectra. Instead of brokenpower law appearance, the mass-velocity diagram of blueshifted lobe can be well fitted by asingle power law with a power indexes of 2 . ± .
23. The mass-velocity diagram of redshiftedlobe can be well fitted by a single power law with a power indexes of 1 . ± .
17 even thoughthe mass drops more rapidly after 25 km s − . As marked by the dashed ellipse in the right panel,the outflow mass revealed by CS (7-6) is much lower than that revealed by HCN (4-3) at veryhigh velocities. Despite the CS data, the mass-velocity diagram of redshifted lobe at velocitiessmaller than 25 km s − can be fitted by a single power law with a much smaller power indexes of1 . ± .
09. However, no significant slope changes are found in both the red- and blue-shiftedlobes of the outflow at the southern core, which are very di ff erent from those previous works. 21 – ff erent evolutionary stages of the three dust cores The northern core has the smallest diameter and mass among the three cores. It seemslikely to be a point source after deconvolution. It is located south of the nominal radio UC H ii region G9.62 + ff use near-IRnebulosity at the west of the radio emission peak (Persi et al. 2003). The reddest one c7(18 h m s ,-20 ◦ ′ ′′ ) is located within 1 ′′ of the radio peak, while the faintest one c8(18 h m s ,-20 ◦ ′ ′′ ) seems to be associated with the sub-mm core detected in SMAobservation. Source c8 is too faint to be detected even at H band and also shows no emissionat 12.5 µ m. In contrast to the bright, rich molecular spectrum forest in the middle and southernsub-mm cores, the northern sub-mm core lacks strong molecular emissions. There is also no otherearly star forming signature such as masers associated with it. Since it is with near-IR emissionand at the edge of the UC H ii region G9.62 + ii region G9.62 + ii region G9.62 + O, and NH (5,5) masers have been detected near the radioemission peak (Forster & Caswell 1989; Hofner et al. 1994; Hofner, & Churchwell 1996a). Peri-odic class II methanol masers are also found in G9.62 + ii regions (Longmore et al. 2007). No infrared source coincides with G9.62 + CN lines are detected in this region, and a kinematictemperature of T k =
108 K was obtained from CH CN emission with LVG model (Hofner et al.1996b), which is coincident with the rotational temperature (T rot =
92 K) obtained from H CSemission. A spectra forest including hot molecular lines, such as CH OH, is detected towardsG9.62 + + µ m dust emission of the southern core peaks at G9.62 + / cm cores (G9.62 + + + ii region excited by a B0.5 star (Hofner et al.1996b). Weaker radio emission was found at core F. H O and OH masers are found across thewhole sub-mm core from north to south (Forster & Caswell 1989; Hofner, & Churchwell 1996a).A near-IR source with large NIR excess is found to be associated with G9.62 + µ m.This object is the dominating and closest associated source of core F. Core F is also confirmed tobe the driving source of an active outflow. All of above imply that G9.62 + Wu et al. (2007) found that UC H ii regions show a higher blue excess than UC H ii precursorswith the IRAM 30 m telescope. Wyrowski et al. (2006) also detected large blue excess in UC H ii regions. ”Blue profile” was detected with CS (7-6) and HCN (4-3) lines in UC H ii regionG9.62 + + + ii phase (Wu et al. 2007; Keto 2002). Around youngercores, the outflow is more active and cold than UC H ii regions, which leads to more ”red profile”. 23 –While in UC H ii regions, the outflows become weak. The surrounding gas of UC H ii regions isthermalized and the temperature gradient towards the central star is more likely to cause ”blueprofile”, which results in the higher blue excess than UC H ii precursors.
5. Summary
We have observed the G9.62 + µ m continuum and molecular lines emission. The main results of this study are as follows:1. Dust continuum at 860 µ m reveals three sub-mm cores in G9.62 + CS as the rotational temperature prober, the temperatures of E and F areestimated to be 92 ±
74 and 51 ±
23 K, respectively. The mass calculated are 13, 30, and 165 M ⊙ forthe northern, middle and southern core.2. In the middle core, HCN (4-3) and CS (7-6) spectra exhibit infall signature. The infall ratecalculated is 4 . × − M ⊙ · yr − . The detection of infall signature in G9.62 + ii phase (Wu et al. 2007).3. In the southern core, high-velocity gas is detected in SO (8 − ), CS (7-6) and HCN (4-3)lines. A bipolar-outflow with a total mass about 26 M ⊙ and a mass-loss rate of 3 . × − M ⊙ · yr − is revealed in SO (8 − ) line wing emission. G9.62 + / SO] and [CS / HCN]in the outflow region are found to be 0.7 and 1.2, respectively. The abundance ratio [CS / HCN]decreases with the flow velocity, indicating smaller outflow regions revealed by CS (7-6) thanthat revealed by HCN (4-3). The mass-velocity diagrams of the blueshifted and redshiftedoutflow lobes can be well fitted by a single power law. The power indexes for the blueshifted andredshifted lobes are 2 . ± .
23 and 1 . ± .
17. No significant slope changes are found in themass-velocity diagrams. 24 –4. The evolutionary sequence of the cm / mm cores in this region are also analyzed. Thenorthern core may be just a remnant core in the envelope of UC H ii region G9.62 + + ii region.Core G9.62 + ii region E and the red profiles at thehot molecular core F supports the results of single-dish observations that UC H ii regions have ahigher blue excess than their precursors. Acknowledgment
We are grateful to the SMA sta ff making the observations. This work is funded by Grants ofNSFC No 10733030 and 10873019. 25 – REFERENCES
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This manuscript was prepared with the AAS L A TEX macros v5.2. 30 – c8 c7 * ** F1 F4 F3 Fig. 1.— The 860 µ m continuum emission image. The contour levels are from 0.03 Jy beam − (3 σ ) in steps of 0.06 Jy beam − (6 σ ). The known cm and mm continuum components (Testi et al.2000) of B, C, D, E, F, G, H, and I are marked by plus signs. Water masers (Hofner, & Churchwell1996a) are marked by open squares and methanol masers (Norris et al. 1993) by triangles. Thenear-IR sources (Persi et al. 2003; Testi et al. 1998; Linz et al. 2005) are marked by filled circles.IRAC sources are marked with asterisks. 31 – F l u x ( Jy ) F l u x ( Jy ) H CNC
S S OH C N C H OH H C S LSBUSB
Fig. 2.— The full LSB and USB spectra in the UV domain over the shortest baseline. The strongestlines are identified and labeled on the plots. 32 – ( ) a ( ) b ( ) c ( ) d ( ) e ( ) f ( ) g ( ) h H CS: (10 -9 ) (10 -9 ) (10 -9 ) (10 -9 ) M i dd l e S ou t he r n Fig. 3.— Integrated intensity maps of four transitions of H CS at the middle (upper panels) andsouthern cores (lower panels). The known cm and mm continuum components are marked by plussigns as in the continuum map. The contour levels in all the panels are from 3 σ in steps of 3 σ . Therms levels are 0.3, 0.3, 0.3 and 0.2 Jy beam − · km s − for H CS (10 , -9 , ) in panels (a) and (e),H CS (10 , -9 , ) in panels (b) and (f), H CS (10 , -9 , ) in panels (c) and (g), and H CS (10 -9 )in panels (d) and (h), respectively. 33 – - - Velocity km s ( / ) ( ) a O ff s e t a r cs e c () ( ) b Fig. 4.— The P-V diagram (left) and First moment map (right) of H CS (10 , -9 , ) emission atthe middle core. (a) The contours of the P-V diagram are from 0.6 to 1.4 in steps of 0.2 Jy beam − (1 σ ). (b) contour plot of H CS (10 , -9 , ) integrated intensity image overlayed on the first momentmap. The contours are from 0.9 (3 σ ) in steps of 0.9 Jy beam − · km s − . The First moment map isconstructed from the data after imposing a cuto ff of 3 σ . 34 – - - velocity km s ( / ) ( ) a ( ) c ( ) b ( ) d I n t en s i t yJy bea m (/) CE Fig. 5.— Spectra and integrated intensity maps of HC N (4-3) (upper panels) and SO (8 − )(lower panels) at the middle core. The systemic velocity is marked with the thick vertical dashedlines at the spectra panels. The known cm and mm continuum components of C, and E are markedby plus signs at the integrated maps as the continuum map. (a) the beam-averaged spectrum ofHC N (4-3) at E, (b) the integrated intensity map of HC N (4-3). The contour levels are -1.2(6 σ ), 1.2, 2.4, 4.2, 6.6, 9.6 Jy beam − · km s − , (c) the beam-averaged spectrum of SO (8 − ) atE. (d) the integrated intensity map of SO (8 − ). The contour levels are -1.2 (6 σ ), 1.2, 2.4, 4.2,6.6, 9.6, 13.2, 17.4, 22.2 Jy beam − · km s − . 35 –Fig. 6.— Beam-averaged spectra and Position-Velocity (P-V) diagrams of HCN (4-3) (upper pan-els) and CS (7-6) (lower panels) at the middle core. The P-V diagrams are cut along a positionangle of 0 ◦ . (a) the beam-averaged spectrum of HCN (4-3) at E, (b) the P-V diagram of HCN(4-3). The contour levels are -1.5 (5 σ ), -0.9, 0.9, 1.5, 2.1, 2.7, 3,3, 3.9, 4.5 Jy beam − , (c) thebeam-averaged spectrum of CS (7-6) at E. (d) the P-V diagram of CS (7-6). The contour levels are-1.5 (5 σ ), -0.9, 0.9, 1.5, 2.1, 2.7, 3,3, 3.9, 4.5 Jy beam − . 36 – ( ) a ( ) b CE Fig. 7.— Integrated intensity maps of HCN (4-3) (left) and CS (7-6) (right) at the middle core.The contour levels in both maps are from 1.5 (5 σ ) in steps of 3 Jy beam − · km s − . HCN (4-3) isintegrated from -3 to 7 km s − , while CS (7-6) from -1 to 6 km s −
37 –Fig. 8.— Averaged spectra of SO (8 − ) (upper-left), HC N (4-3) (lower-left), HCN (4-3)(upper-right) and CS (7-6) (lower-right) at the southern core. The spectra of SO (8 − ) andHC N (4-3) are averaged over a region of 4 ′′ , while HCN (4-3) and CS (7-6) are averaged over aregion of 6 ′′ . HCN ν = ( ) a ( ) b HI GFD
Fig. 9.— The integrated intensity maps of HC N (4-3) (left panel) and SO (8 − ) (right panel)at the southern core. To avoid the influence of outflow motions, both the maps are integrated from2 km s − to 8 km s − . The contour levels are (a) -1.2 (6 σ ), 1.2, 2.4, 4.2, 6.6, 9.6, 13.2, 17.4Jy beam − · km s − for HC N (4-3), (b) -1.2 (6 σ ), 1.2, 2.4, 4.2, 6.6, 9.6, 13.2, 17.4, 22.2, 27.6, 33.6Jy beam − · km s − for SO (8 − ) 39 –Fig. 10.— P-V diagrams and integrated intensity maps of SO (8 − ) (upper panels), and HC N(4-3) (lower panels) at the southern core. The P-V diagrams are cut along N-S direction. Thevertical solid line in P-V diagrams labels the systemic velocity. The dashed and solid contoursin the right panels show the red- and blue-shifted emission, respectively. The integral velocityintervals are marked by thick dashed lines in the P-V diagrams. For both SO (8 − ) and HC N(4-3), the blue-shifted emission is integrated from -4 km s − to 0 km s − , while the red-shiftedemission from 10 km s − to 14 km s − in the integrated intensity maps. (a) P-V diagram of SO(8 − ). The contours are from 0.6 (3 σ ) in steps of 0.6 Jy beam − . (b) P-V diagram of HC N(4-3). The contours are from 0.6 (3 σ ) in steps of 0.4 Jy beam − . (c) Integrated intensity maps ofSO (8 − ) at line wings. The contours are from 1 (5 σ ) in steps of 1 Jy beam − · km s − for bothred- and blue-shifted emission. (d) Integrated intensity maps of HC N (4-3) at red wing. Thecontours are 0.6 (3 σ ), 1.2, 2, 3 Jy beam − · km s − . 40 –Fig. 11.— CS (7-6) channel maps at the southern core, which is smoothed to a velocity resolutionof 3 km s − . The contours are -0.6 (3 σ ), 0.6, 1.2, 2.4, 4.8, 7.2, 9.6 Jy beam − . 41 –Fig. 12.— HCN (4-3) channel maps at the southern core, which is smoothed to a velocity resolutionof 4 km s − . The contours are -0.6 (3 σ ), 0.6, 1.2, 2.4, 3.6, 4.8, 7.2 Jy beam − . 42 – - - -
10 0 10 20 30 40 50 Ve l oc it y km s ( / ) - - - - O ff s e t a r cs e c () ( ) a ( ) b ( ) c ( ) d ( ) e HI GF D
Fig. 13.— P-V diagrams and integrated intensity maps of HCN (4-3) (upper panels), and CS (7-6)(lower panels) at the southern core. The P-V diagrams are cut along N-S direction. The verticalsolid line in P-V diagrams labels the systemic velocity. The dashed and solid contours in the rightpanels show the red- and blue-shifted emission, respectively. The blue- and red-shifted emissionin the integrated maps are integrated from -12 km s − to -5 km s − and 15 km s − to 22 km s − ,respectively in (b) and (e) panels. (a) P-V diagram of HCN (4-3). The contours are from 0.9 (3 σ )in steps of 1.2 Jy beam − . (b) Integrated intensity maps of HCN (4-3) at line wings. The contoursare 1.5 (5 σ ), 4.5, 7.5, 10.5 Jy beam − · km s − . (c) The integrated intensity maps of HCN (4-3) atextremely high velocities. The blue- and red-shifted emission in the integrated maps are integratedfrom -20 km s − to -13 km s − and 23 km s − to 39 km s − , respectively. The contours are from 1.5(5 σ ) in steps of 3 Jy beam − · km s − for both blue- and red-shifted emission. (d) P-V diagram ofCS (7-6). The contours are from 0.9 (3 σ ) in steps of 1.2 Jy beam − . (e) Integrated intensity mapsof CS (7-6) at line wings. The contours are 1.5 (5 σ ), 4.5, 7.5, 10.5 Jy beam − · km s −
43 –
50 100 150 200 25022 E u (K) l n ( N u / g u ) N tot = (4.2 ± × cm −2 T rot = 42 ±
34 K f = 0.46 ± core D E u (K) l n ( N u / g u ) N tot = (3.6 ± × cm −2 T rot = 92 ±
74 K f = 0.26 ± core E u (K) l n ( N u / g u ) N tot = (4.0 ± × cm −2 T rot = 51 ±
23 K f = 0.34 ± core F 0 100 200 300 400 5002224262830 E u (K) l n ( N u / g u ) N tot = (3.7 ± × cm −2 T rot = 105 ±
37 K f = 0.12 ± core G Fig. 14.— Population diagrams of H CS towards four cm / mm cores. The names of the cores arelabeled on the upper-right corner of each panel. Open circles in blue represent the observed data.The vertical bars present 3 σ errors of ln(N u / g u ) due to the uncertainties of integrated intensities.The solid line shows the linear least-squares fitting using the Rotational Temperature Diagrammethod. Crosses in red mark the weighted mean results from Population Diagram analysis. Theinferred parameters from the Population Diagram analysis are presented on the upper-right cornersof each panel. 44 – V flow (km/s) [ C S / S O ]
10 K20 K30 K50 K40 K flow (km/s) [ C S / HCN ] (b) [CS/HCN] = −0.064 × V flow + 1.795 R = 0.91 Fig. 15.— Abundance ratios of [CS / SO] (left) and [CS / HCN] (right) versus flow velocity along theredshifted lobe. We range the excitation temperature from 10 K to 50 K to derive the abundanceratios of [CS / SO]. The excitation temperature in calculation of abundance ratios of [CS / HCN] isassumed to be 30 K. The solid line in the right panel is the linear least-squares fitting, and thefitting results are presented in the upper-right corner. 45 –
105 15 20 2510 −2 −1 V flow (km/s) M ( M s un ) SOCSHCN(a) γ = 2.28 ± = 0.78
105 15 20 25 30 3510 −2 −1 V flow (km/s) M ( M s un ) SOCSHCN(b) γ = 1.08 ± = 0.87 γ = 1.70 ± = 0.73 Fig. 16.— Mass-Velocity relationships for the outflow lobes. Left : blueshifted lobe; right: red-shifted lobe. The solid lines in both panels show the power law fit towards all the data. Thedashed line in the right panel shows the power law fit towards the HCN and SO data up toV f low =
25 km s − . The fitting results are presented in the lower-left corners. 46 –Table 1. Parameters of 860 µ m continuum emission R.A. Decl. Deconvolution sizes I peak S ν T d a β a Mass N H Name (J2000) (J2000) ( ′′ × ′′ ) (Jy beam − ) (Jy) (K) (M ⊙ ) (10 cm − )Northern core 18:06:14.447 -20:31:28.253 Point source 0.20 ± . ′′ × . ′′ (P.A. = − . ◦ ) 0.76 ± . ′′ × . ′′ (P.A. = − . ◦ ) 0.95 ± a The dust temperature is assumed to be the same as the rotational temperature of H CS transitions b The opacity index β is obtained from Su et al. (2005) Table 2. Observed parameters of the lines
Molecule Transition Frequency E u rms V lsr b Intensity b FWHM b (GHz) (K) (Jy beam − ) (km s − ) (Jy beam − ) (km s − )D E F G D E F G D E F GH CS 10 , -9 , ± ± ± ± ± ± ± ± ± ± ± ± , -9 , ± ± ± ± ± ± ± ± ± , -9 , ± ± ± ± ± ± ± ± ± , -9 , ± ± ± ± ± ± ± ± ± , -9 , ± ± ± ± ± ± ± ± ± ± ± ± , / -9 , / ± ± ± ± ± ± ± ± ± -7 ± ± ± ± ± ± ± ± ± ± ± ± N ν = ± ± ± ± ± ± ± ± ± ± ± ± ν = a Not all the detected lines are listed in this table. The others will be presented in another paper. b The V lsr , Intensity and FWHM of each transition are derived from single gaussian fit towards the beam-averaged spectra. b Blended with H
CO (5 , -4 , ) at 343.325713 GHz. d Blended with H CS (10 , -9 , ) e Blended with H CS (10 , -9 , ) f The two transitions of H CS (10 , -9 , ) and (10 , -9 , ) have the same frequency, line strength and permanent dipole moment. Therefore they has same contributions to the observedline profile. Table 3. The physical parameters of H CS transitions obtained with Rotational Temperature Diagram (RTD) method andPopulation Diagram (PD) analysis
Core RTD PDT rot (K) N tot (10 cm − ) T rot (K) N tot (10 cm − ) f τ (10 , -9 , ) (10 , -9 , ) (10 , -9 , ) (10 , -9 , ) (10 , -9 , ) (10 , / -9 , / )D 43 ± ± ±
34 4.2 ± ± ± ± ± ± ± ±
21 2.5 ± ±
74 3.6 ± ± ± ± ± ± ± ± ± ± ±
23 4.0 ± ± ± ± ± ± ± ±
17 1.3 ± ±
37 3.7 ± ± ± ± ± ± a The rotational temperature and total column density of H CS transitions derived from RTD analysis are presented in the second and third columns, while those derived from PDanalysis are shown in the forth and fifth columns. The sixth column gives the filling factor of each source inferred from PD analysis. The last six columns exhibit the optical depth of eachtransition using PD analysis.
49 –Table 4. Outflow parameters of the southern core
Molecule Velocity interval M P E(km s − ) (M ⊙ ) (M ⊙ · km s − ) (1045