High-sensitivity millimeter imaging of molecular outflows in nine nearby high-mass star-forming regions
De-Jian Liu, Ye Xu, Ying-Jie Li, Sheng Zheng, Deng-Rong Lu, Chao-Jie Hao, Ze-Hao Lin, Shuai-Bo Bian, Li-Ming Liu
DDraft version December 8, 2020
Typeset using L A TEX default style in AASTeX63
High-sensitivity millimeter imaging of molecular outflows in nine nearby high-mass star-formingregions
De-Jian Liu,
1, 2
Ye Xu, Ying-Jie Li, Sheng Zheng, Deng-Rong Lu, Chao-Jie Hao,
2, 3
Ze-Hao Lin,
2, 3
Shuai-Bo Bian,
2, 3 and Li-Ming Liu College of Science, China Three Gorges University, Yichang 443002, Peoples Republic of China; Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, Peoples Republic of China; School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, Peoples Republic of China;
ABSTRACTWe present a study of molecular outflows using six molecular lines (including CO/ CO/C O/HCO + ( J = 1 −
0) and CS/SiO ( J = 2 − CO, CO, HCO + , and CS) is 100%. However,the emission of SiO was not detected for all sources. The full line widths (∆ V ) at 3 σ above the baselineof these molecular lines have the relationship ∆ V CO > ∆ V HCO + > ∆ V CS ≈ ∆ V CO > ∆ V CO . CO and HCO + can be used to trace relatively high-velocity outflows, while CO and CS can beemployed to trace relatively low-velocity outflows. The dynamical timescales of the CO and CSoutflows are longer than those of the CO and HCO + outflows. The mechanical luminosities, masses,mass-loss rates and forces of all outflows (including CO, CO, HCO + , and CS) are correlated withthe bolometric luminosities of their central IRAS sources. Keywords:
Jets (870), Interstellar clouds (834), Star formation (1569) INTRODUCTIONThe physical processes associated with low-mass star formation are reasonably well understood (e.g., Shu et al.1987; McKee & Ostriker 2007; Kennicutt & Evans 2012). However, details of the forming mechanism(s) of high-massstars remain poorly understood, so creating a clear map of high-mass star formation is extremely challenging work.To achieve this goal, it is vital to study molecular outflows, which arise during an important phase in high-mass starformation and are a ubiquitous phenomenon during the earliest stage of formation for stars of all masses (Beutheret al. 2002; Arce et al. 2007).Since molecular outflows were first detected in Orion KL by Kwan & Scoville (1976), outflows in high-mass star-forming regions (HMSFRs) have been investigated by many researchers (Shepherd & Churchwell 1996; Zhang et al.2001, 2005; Xu et al. 2006b; Li et al. 2018, 2019). In each of these studies, typically only one outflow tracer wasused. However, there is no perfect outflow tracer, and a complete characterization of outflow phenomena requiresobservations made with many tracers (Bally 2016). Hence, to provide a more comprehensive understanding of thephysical properties of outflows, it is necessary to conduct systematic studies of different molecular outflows usingmultiple molecular tracers toward HMSFRs.Accurate distances over a relatively narrow distance range are important to statistically analyze the physical prop-erties of outflows. Typical selection criteria in terms of distance have been commonly used: (1) the distances aremeasured by the trigonometric parallaxes of masers, which are typically more accurate than kinematic distances (Xuet al. 2006a; Reid et al. 2019), so more accurate physical quantities can be ascertained; (2) the sources are nearby andwithin a relatively narrow distance range (i.e., 0.5–1 kpc). In the context of PMODLH, the linear resolution can be
Corresponding author: Ye [email protected] a r X i v : . [ a s t r o - ph . GA ] D ec Liu et al.
Table 1.
List of objects.
ID IRAS Name Other Name R.A.(J2000) Decl.(J2000) Dist (kpc) Ref(s)(1) (2) (3) (4) (5) (6) (7)1 00338+6312 L1287 00:36:47.4 63:29:02 0.9 12 05345+3157 G176.51+00.20 05:37:52.1 32:00:03 1.0 23 06053-0622 Mon R2 06:07:47.9 -06:22:56 0.8 2, 34 06384+0932 NGC2264 06:41:09.9 09:29:14 0.7 4, 55 21007+4951 G090.21+02.32 21:02:22.7 50:03:08 0.7 66 21418+6552 G105.41+09.87 21:43:06.5 66:06:55 0.9 3, 67 22198+6336 ... 22:21:26.7 63:51:37 0.8 78 22272+6358 A L1206 22:28:51.4 64:13:41 0.8 19 22543+6413 Cep A 22:56:18.1 62:01:49 0.7 3, 8
Note — (1) ID. (2) and (3) Source name(s). (4) and (5) Position of the source (R.A.: hh:mm:ss.s, Decl.: dd:mm:ss). (6):Distance to the source. (7): Parallax reference.
References —(1) Rygl et al. (2010); (2) Xu et al. (2016); (3) Plume et al. (1992); (4) Kamezaki et al. (2014); (5) Schreyeret al. (1997); (6) Xu et al. (2013); (7) Hirota et al. (2008); (8) Moscadelli et al. (2009)better than 0.27 pc with beam size of ∼ (cid:48)(cid:48) . This resolution is usually sufficient to visually depict the morphology ofoutflows, where the typical length of an outflow is about 1 pc.This work is the first high-sensitivity systematic research of outflows, which was conducted using six molecular lines(i.e., SiO ( J = 1 − J = 2 − + ( J = 1 − CO ( J = 1 − CO ( J = 1 − O ( J = 1 − O. Meanwhile, the molecular outflows were imagined using CO, CO, HCO + , and CS, which were utilized totrace areas of different densities in HMSFRs. These lines were observed by the same telescope with high-sensitivityobservations and binned to the same pixel scales, which allowed us to make direct comparisons between the differentline tracers. Additionally, the high-sensitivity observations were helpful for unvieling high-velocity outflow gas.The remainder of the paper is organized as follows. We present the observations and data-reduction techniques inSection 2. In Section 3, we summarize the detected outflows and calculate the relevant physical quantities and therelationships between them. Finally, a summary of our work is given in Section 4. OBSERVATIONSThe observations of nine HMSFRs were carried out from July 2019 to May 2020 using the PMODLH 14-m millimeters-wavelength telescope. The detailed observations of the six molecular lines are: (1) CO ( J = 1 − CO ( J = 1 − O ( J = 1 − J = 2 − + ( J = 1 − J = 2 − CO, and C O were in the lowersideband, and CO, HCO + , and CS were in the upper sideband.The lines of SiO were obtained via the single pointing observation mode with integration times over 40 min. Otherlines were observed with the on-the-fly (OTF) mode, using typical sample steps of 10 (cid:48)(cid:48) –15 (cid:48)(cid:48) . The OTF raw data weregridded in a FITS cube with a pixel size of 30 (cid:48)(cid:48) using the GILDAS software package. The typical integration timefor each position was about 15 min. Each fast Fourier transform (FFT) spectrometer with a bandwidth of 1 GHz utflows in nine sources Table 2.
Basic observation parameters at the observed frequencies.
No Lines T sys (K) η mb HPBW ( (cid:48)(cid:48) ) Velocity resolution (km s − )(1) (2) (3) (4) (5) (6)1 CO 250-300 0.49 49 0.1592 CO 150-200 0.54 51 0.1663 C O 150-200 0.54 52 0.1664 SiO 100-150 0.58 62 0.2055 HCO + Note — (1) No. (2) Molecular line. (3) Typical system temperature ( T sys ). (4) Main beam efficiency( η mb ). (5) Half power beam width (HPBW). (6) Velocity resolution.provided 16384 channels, producing a spectral resolution of 61 kHz. The parameters of the antenna and the velocityresolutions of the spectrometers are listed in Table 2. All results presented in this work are expressed as brightness temperatures, T ∗ R = T ∗ A /η mb , where T ∗ A is the antennatemperature and η mb is the main beam efficiency, which are listed in Table 2. The main beam root-mean-square (RMS)noises of the molecular lines for all observed sources are listed in Table 3. RESULTS3.1.
Emission Peak spectra
We successfully detected CO, CO, C O, HCO + , and CS emission from all sources; unfortunately, we did notdetect SiO emission for all sources.The basic parameters of the molecular lines at the respective emission peaks are listed in Table 4. Meanwhile, themolecular line profiles of the emission peak of C O for each source are shown in Figure 1. To select the most suitablesensitivity to achieve maximum telescope efficiency, the following tests were performed for the CS observation of CepA. When the integration time of each position was about 15 min, the RMS noise was about 15.9 mK, and the fullwidth (∆ V ) at 3 σ above the baseline was 16.8 km s − . Then we doubled the integration time (i.e., to 30 min), findingan RMS noise of about 10.2 mK, and a full width of 17.7 km s − . There was no significant extension of its full width.Hence, we chose 15 min as the typical integration time of each position. Our results indicate the following relationship:∆ V CO > ∆ V HCO + > ∆ V CS ≈ ∆ V CO > ∆ V CO . Meanwhile, multiple velocity features were visible in some lineprofiles, particularly those of CO and HCO + , while CO, C O, and CS were quite smooth.SiO emission, which was used as a shock tracer, was not detected for all sources (see Figure 2). These sources hadalso been observed by Harju et al. (1998), who attempted to correlate the SiO emission with maser characteristicsand with ultra-compact (UC) H II regions. In their work, Harju et al. (1998) used the 15-m telescope Swedish-ESOSubmillimetre Telescope (SEST) and the 20-m radio telescope of the Onsala Space Observatory in Sweden. Of thenine sources considered here, Harju et al. (1998) only detected SiO emission for L1287 with Onsala, whose velocityresolution was 0.17 km s − and RMS was 20 mK, which were similar to what we achieved with our observations. Thus,the velocity resolution and sensitivity of PMODLH might not be the reason why we did not detect any SiO emissionfrom L1287. Whilst the half power beam width (HPBW) of Onsala (i.e., 43 (cid:48)(cid:48) ) was better than that of PMODLH (i.e.,62 (cid:48)(cid:48) ). Harju et al. (1998) pointed out that SiO emission can be better traced by telescopes with higher resolutions (e.g.a 30-m telescope, which has a larger aperture). Therefore, resolution might be the reason why we did not detect SiOemission for all sources. Liu et al.
Table 3.
Main beam RMS noise.
Source RMS Noise (mK)SiO CS HCO + 12 CO CO C O(1) (2) (3) (4) (5) (6) (7)L1287 14.3 15.1 16.9 51.2 29.8 28.1G176.51+00.20 18.1 15.3 17.2 60.9 32.8 31.5Mon R2 15.3 15.6 18.3 51.1 25.7 24.2NGC2264 14.5 16.1 16.3 47.4 27.5 25.9G090.21+02.32 16.8 13.4 17.7 66.9 36.4 32.8G105.41+09.87 17.8 13.2 17.2 50.0 27.5 27.0IRAS 22198+6336 16.4 14.7 13.5 44.0 23.7 26.1L1206 14.8 16.7 17.9 43.6 27.4 25.8Cep A 15.3 10.2 21.4 50.8 32.0 29.4
Note — (1) Source name. (2), (3), (4), (5), (6) and (7) RMS noise of SiO, CS, HCO + , CO, CO, and C O, respectively. utflows in nine sources
40 20 0 20010 CO40 20 0 2005 CO40 20 0 2001 T R * ( K ) C O40 20 0 2005 HCO +
40 20 0 20V
LSR (km s )0.02.5 CS (a) L1287 CO05 CO01 T R * ( K ) C O0.00.5 HCO +
40 20 0V
LSR (km s )0.00.5 CS (b) G176.51+00.20 CO010 CO01 T R * ( K ) C O0.02.5 HCO +
20 0 20 40V
LSR (km s )05 CS (c) Mon R2 CO0 20010 CO0 2002 T R * ( K ) C O0 2005 HCO + LSR (km s )0.02.5 CS (d) NGC2264
20 0 2005 CO20 0 200.02.5 CO20 0 2001 T R * ( K ) C O20 0 200.00.5 HCO +
20 0 20V
LSR (km s )0.00.5 CS (e) G090.21+02.32
20 0020 CO 20 005 CO 20 00.00.5 T R * ( K ) C O 20 002 HCO +
20 0V
LSR (km s )01 CS (f) G105.41+09.87
20 0010 CO 20 005 CO 20 002 T R * ( K ) C O 20 002 HCO +
20 0V
LSR (km s )01 CS (g) IRAS 22198+6336 CO05 CO02 T R * ( K ) C O02 HCO +
20 10 0V
LSR (km s )01 CS (h) L1206
50 0020 CO50 0010 CO50 002 T R * ( K ) C O50 00.02.5 HCO +
50 0V
LSR (km s )02 CS (i) Cep A Figure 1.
Line profiles of the molecular transitions for the nine HMSFR sources. The spectra were obtained at the positionof the C O emission peak. The name of each source is given at the bottom of each panel. From top to bottom the lines are CO, CO, C O, HCO + , and CS. Liu et al. T a b l e . B a s i c p a r a m e t e r s o f t h e m o l e c u l a r li n e s . C O C O C O H C O + C S S o u r ce T ∗ R V p e a k ∆ V T ∗ R V p e a k ∆ V T ∗ R V p e a k ∆ V T ∗ R V p e a k ∆ V T ∗ R V p e a k ∆ V ( K )( k m s − )( k m s − )( K )( k m s − )( k m s − )( K )( k m s − )( k m s − )( K )( k m s − )( k m s − )( K )( k m s − )( k m s − ) ( )( )( )( )( )( )( )( )( )( )( )( )( )( )( )( ) L . - . . . - . . . - . . . - . . . - . . G . + . . - . . . - . . . - . . . - . . . - . . M o n R . . . . . . . . . . . . . . . N G C . . . . . . . . . . . . . . . G . + . . . . . . . . . . . . . . . . G . + . . - . . . - . . . - . . . - . . . - . . I R A S + . - . . . - . . . - . . . - . . . - . . L . - . . . - . . . - . . . - . . . - . . C e p A . - . . . - . . . - . . . - . . . - . . N o t e — ( ) S o u r ce n a m e . ( ) , ( ) , ( ) , ( ) a nd ( ) B r i g h t n e ss t e m p e r a t u r e ( s ) o f t h ee m i ss i o np e a k s o f C O , C O , C O , H C O + , a nd C S , r e s p ec t i v e l y . ( ) , ( ) , ( ) , ( ) a nd ( ) C e n tr a l v e l o c i t i e s o f C O , C O , C O , H C O + , a nd C S , r e s p ec t i v e l y . ( ) , ( ) , ( ) , ( ) a nd ( ) F u ll li n e w i d t h a t σ a b o v e t h e b a s e li n e o f C O , C O , C O , H C O + , a nd C S , r e s p ec t i v e l y . utflows in nine sources T a b l e . O u t fl o w p a r a m e t e r s . C O C O H C O + C S S o u r ce ∆ v b ( k m s − ) ∆ v r ( k m s − ) ∆ v b ( k m s − ) ∆ v r ( k m s − ) ∆ v b ( k m s − ) ∆ v r ( k m s − ) ∆ v b ( k m s − ) ∆ v r ( k m s − ) ( )( )( )( )( )( )( )( )( ) L ( - , - )( - , - )( - , - )( - , - )( - , - )( - , - )( - , - )( - , - ) G . + . ( - , - )( - , - )( - , - )( - , - )( - , - )( - , )( - , - )( - , - ) M o n R ( - , )( , )( , )( , )( , )( , )( - , )( , ) N G C ( - , )( , ) ... ( , )( - , )( , )( - , )( , ) G . + . ... ( , ) ... ( , ) ... ( , ) ... ( , ) G . + . ( - , - )( - , )( - , - )( - , - )( - , - )( , )( - , - )( - , - ) I R A S + ( - , - )( - , )( - , - ) ... ( - , - )( , )( - , - )( - , - ) L ( - , - )( - , - )( - , - )( - , - )( - , - )( - , - )( - , - )( - , - ) C e p A ( - , - )( - , )( - , - )( - , - )( - , - )( - , )( - , - )( - , ) N o t e — ( ) S o u r ce n a m e . ( ) – ( ) O u t fl o w v e l o c i t y r a n g e s ( ∆ v ) f o rt h e b l u e a nd r e d w i n g s o f C O , C O , H C O + , a nd C S , r e s p ec t i v e l y . Liu et al.
25 0 250.10.00.1 L1287 25 0 25G176.51+00.20 25 0 25Mon R225 0 250.10.00.1 T * R ( K ) NGC2264 25 0 25G090.21+02.32 25 0 25G105.41+09.8725 0 250.10.00.1 IRAS 22198+6336 25 0 25V
LSR (km s )L1206 25 0 25Cep A Figure 2.
SiO spectra of the nine sources, including null detections. The name of each source is given in the top left-handcorner of each panel.
Outflow morphology
This work represents the first time that four molecular outflow tracers have been used in a single work ( CO, CO,HCO + , and CS), in addition to one shock tracer (SiO) and one dense core tracer (C O). With our observations, wesuccessfully detected outflows associated with all nine sources. The high detection rate of outflows suggests that CO, CO, HCO + , and CS may be all suitably used to trace the molecular outflows of HMSFRs.Outflow maps are presented in Figures 3–11. Within these figures, we have plotted the CO, CO, HCO + , andCS contours overlaid on the C O integrated images and WISE false-color images (Wright et al. 2010), where blue,green, and red correspond to the 4.6, 12, and 22 µ m data, respectively. To determine the possible excitation sourcesof these outflows, we also marked the positions of the associated IRAS sources in the images, which were obtainedfrom the IRAS Point Source Catalog 2.1. The bolometric luminosities of these IRAS sources were sourced fromSanders & Mirabel (1996). Meanwhile, the plotted spectra which have been smoothed to 5 δv (i.e., we smoothed thedata by merging five channels into a one channel) at the emission peaks of the blue and red lobes, and marked outthe velocity ranges of the outflows using different color shades (see Figure 3 for details). The velocity ranges of thedifferent outflows are listed in Table 5. Our main results are summarized as follows:1. CO molecular outflows were detected for all sources. Eight sources (L1287, G176.51+00.20, Mon R2, NGC2264,G105.41+09.87, IRAS 22198+6336, L1206, and Cep A) showed clear bipolar or multiple outflow structures. Amongthem, the outflow of IRAS 22198+6336 was mapped for the first time, and NGC2264 was found to contain bipolaroutflows for the first time. G090.21+02.32 appeared to show only a red lobe, although the source had been previouslyidentified as a bipolar outflow (Clark 1986). The velocity ranges of the outflows of four sources (L1287, G176.51+00.20,Mon R2, and Cep A) have been extended with the improved high-sensitivity observations.2. We detected CO molecular outflows for the first time for all sources. Six sources (L1287, G176.51+00.20, MonR2, G105.41+09.87, L1206, and Cep A) showed clear bipolar or multiple outflow structures. Three sources (NGC2264,G090.21+02.32, and IRAS 22198+6336) appeared to present a one-sided lobe, i.e., NGC2264 and G090.21+02.32showed only a red lobe, and IRAS 22198+6336 presented only a blue lobe. https://irsa.ipac.caltech.edu/Missions/wise.html https://irsa.ipac.caltech.edu/Missions/iras.html utflows in nine sources
93. We detected HCO + molecular outflows for all sources. Eight sources (L1287, G176.51+00.20, Mon R2,NGC2264, G105.41+09.87, IRAS 22198+6336, L1206, and Cep A) showed clear bipolar or multiple outflow struc-tures. G090.21+02.32 showed only a red lobe. Except for L1287 and Cep A, the HCO + outflows of the other sourceswere mapped for the first time.4. We detected CS molecular outflows for the first time for all sources. Except for G090.21+02.32, which showed onlya red lobe, the other eight sources (L1287, G176.51+00.20, Mon R2, NGC2264, G105.41+09.87, IRAS 22198+6336,L1206, and Cep A) presented clear bipolar or multiple outflow structures.3.2.1. L1287
The CO bipolar outflows of L1287 were first detected by Snell et al. (1990), and confirmed by Yang et al. (1991);Xu et al. (2006b). Benefitting from our high-sensitivity observations (see Table 3), the velocity range of the blue lobeof this source has been extended from −
31 km s − (Yang et al. 1991) to −
34 km s − . The − − component inthe red line wing was contaminated, so the velocity range cannot be extended. After updating the velocity range, thestructure of the bipolar outflow remained unchanged. It is aligned along the northeast–southwest direction (see panel(a1) of Figure 3), which is similar to the results of Snell et al. (1990); Yang et al. (1991); Xu et al. (2006b).L1287’s HCO + outflow was mapped by Yang et al. (1991). The velocity ranges have been extended with our datafrom − − to − − for the blue lobe, and from − − to − − for the red lobe. Ourresults are similar to those of Yang et al. (1991).The CO and CS outflows of L1287 were also detected (see panels (c1) and (d1) of Figure 3, respectively), whichare also aligned along the northeast–southwest direction. However, the distances between the emission peaks of thered and blue lobes of the CO, HCO + and CS outflows are smaller than those of CO. Compared with the COoutflow, the locations of the other three outflows are shifted a little to the southeast direction, so that the midpointof the red and blue lobes is closer to the position of the IRAS source. Meanwhile, both the CO and HCO + outflowshave larger blue lobes than red ones, while the sizes of the two lobes for CO and CS are similar.IRAS 00338+6312 (see the star in Figure 3) is located at the center of these bipolar outflows. There is also WISEemission located at the center of the four groups of bipolar outflows. The core traced by CS, HCN, HCO + , and NH (Walker & Masheder 1997; Zinchenko et al. 1997) are all associated with the IRAS source. Meanwhile, the emissionpeak of C O is associated with the IRAS source. All of these tracers seem to indicate that the same source drives allthe bipolar outflows. 3.2.2.
G176.51+00.20
The velocity range has been extended from −
30 km s − to −
47 km s − in the blue wing and from − − to − − in the red wing of the CO outflow from G176.51+00.20 (which is also named AFGL 5157, and NGC 1985,Snell et al. 1988, see panel (a1) of Figure 4). The CO bipolar outflows are along the east–west direction, which iscoincident with the results of the study of Snell et al. (1988).The bipolar outflows of HCO + , CO, and CS have been mapped for the first time in this work (see panels (b1),(c1), and (d1) of Figure 4, respectively). The directions of the HCO + , CO, and CS outflows are similar to those ofthe CO outflows. The distances between the emission peaks of the red and blue lobes of the HCO + , CO, and CSoutflows are also smaller than those of CO. Different from the other outflows, however, the red and blue lobes of theCS outflow are very close to each other, and its structure is not as extended as the other outflows. We also found thatthe velocity range of the red lobe of the HCO + outflow is even broader than that of the CO outflow (see Table 5and Figure 4).There is WISE emission located at the center of bipolar outflows, which could be the source of excitation. Althoughthe emission is faint, it is associated with the emission peak of C O. The nearest IRAS source, IRAS 05345+3157(see the star in Figure 4), is located near the emission peak of the blue lobe, and it might be the source of excitationof the outflows. 3.2.3.
Mon R2
We detected CO, HCO + , CO, and CS outflows in Mon R2. The CO bipolar outflow of Mon R2 has beenwidely studied by many researchers (Bally & Lada 1983; Meyers-Rice & Lada 1991; Xu et al. 2006b). The velocityrange of the red wing of the CO outflow has been extended from 22 km s − (Meyers-Rice & Lada 1991) to 30 kms − . This source is so complex that observations with different resolutions may result in different structural detailsof its outflows. With beam size used here (i.e., ∼ (cid:48)(cid:48) ), the pair of bipolar outflow in the north (see Xu et al. 2006b)0 Liu et al.
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 010 T R * ( K ) (a3)50 0V LSR (km s )010 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 20 0012 T R * ( K ) (b3)(b3) 20 0V LSR (km s )012 T R * ( K ) (b4)(b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 024 T R * ( K ) (c3)50 0V LSR (km s )024 T R * ( K ) (c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 012 T R * ( K ) (d3)40 20 0V LSR (km s )02 T R * ( K ) (d4) (d) CS Figure 3.
Profile maps of the outflow in L1287. (a1) Integrated C O map with CO blue/red lobe contours (whose levelsare from 30% to 90% of the peak intensity of each lobe). The blue star represents the IRAS source (IRAS 00038+6312). Thewhite dot is the emission peak of C O. Position (0, 0) represents the coordinates of the source (see details in Table 1). (a2)The background shows a false-color RGB WISE image constructed using 4.6 (blue), 12 (green), and 22 µ m (red) data, whilethe other features are the same as in panel (a1). (a3) Blue spectrum of CO at the blue emission peak position of the COoutflow. The data have been smoothed to 5 δv . The blue shading of the spectrum indicates the blue line wing velocity of CO.(a4) Red spectrum of CO at the red emission peak position of the CO outflow. The data have been smoothed to 5 δv . Thered shading of the spectrum indicates the red line wing velocity of CO. For the other subpanels, the descriptions are the sameas in panels (a1–a4), but the outflows are of (b1–b4) CO, (c1–c4) HCO + , and (d1–d4) CS. partly overlap with the southern bipolar outflow and perhaps also with some surrounding gas. Therefore, the outflowappears relatively extended (see panel (a1) of Figure 5). This morphology is similar to the outflow shown in figure 1in Meyers-Rice & Lada (1991), where their beam size ( ∼ (cid:48)(cid:48) ) was similar to ours. Thus, the structure ascertained inthis work is similar to that of Meyers-Rice & Lada (1991), the second pair of bipolar outflows is hard to be separatedunder current resolution, which might be interferenced by other components.The HCO + , CO, and CS outflows of this source were mapped for the first time here. Comparing the four groupsof outflows, both the CO and HCO + outflows present two red and blue emission peaks, although these peaks arehard to separate from each other. However, the two peaks in the red lobe of the CS outflow could be easily separated.Furthermore, from the CO outflow, only one emission peak can be seen in the red lobe (see Figure 5).IRAS 06053-0622 is located at the center of the bipolar outflows and near the emission peak of C O. Meanwhile,the WISE emission of this region is so strong that the WISE data are saturated. All of these tracers seem to indicatethat the IRAS source is the source of excitation of these outflows. utflows in nine sources
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 010 T R * ( K ) (a3)50 25 0V LSR (km s )0510 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 20 0012 T R * ( K ) (b3)(b3) 20 0V LSR (km s )012 T R * ( K ) (b4)(b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 0.00.20.4 T R * ( K ) (c3)(c3)50 25 0V LSR (km s )0.00.20.4 T R * ( K ) (c4)(c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 0.00.2 T R * ( K ) (d3)(d3)40 20 0V LSR (km s )0.00.2 T R * ( K ) (d4) (d) CS Figure 4.
Profile maps of the outflows from G176.51+00.20. The description of each map is the same as that in Figure 3,except the blue star is IRAS 05345+3157.
NGC2264
Previously, only a CO red lobe was detected toward NGC2264 (Bally & Lada 1983; Margulis et al. 1988); however,we have also detected a blue lobe (see panel (a1) of Figure 6). Therefore, the CO outflow of NGC2264 is not, as oncebelieved, a one-side red lobe, but instead is a bipolar outflow. The emission in the north is so strong (see blue contourin panel (a1) of Figure 6) that it has a disastrous effect on the mapping process of its blue lobe outflow; hence, theblue lobe is easily to be ignored. Thanks to the high-sensitivity observations obtained with PMODLH, we successfullymapped the blue lobe of the outflow.The CO, HCO + , and CS outflows of this source were detected for the first time. Except for CO, the otheroutflows of this source are bipolar and distributed along the east–west direction. In fact, the blue line wings of COis higher than the Gaussian fitting, but the structures of the blue lobe in the contour map are too chaotic. Hence, theblue lobe of CO, if present, was not detected. The intensities of the blue lobes of HCO + and CS are stronger thanthat of CO (see Figure 6).IRAS 06384+0932 is located at the center of the bipolar outflows. Meanwhile, the WISE emission near the outflowis saturated in this region. Furthermore, the emission peak of C O is also near the IRAS source and WISE emission.Therefore, IRAS 06384+0932 may be the source of excitation of the outflows.3.2.5.
G090.21+02.32 Liu et al.
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 0 25020 T R * ( K ) (a3) 0 25V LSR (km s )020 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 0 200510 T R * ( K ) (b3)0 20V LSR (km s )0510 T R * ( K ) (b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 0 2002 T R * ( K ) (c3) 0 20V LSR (km s )024 T R * ( K ) (c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 0 200.00.20.4 T R * ( K ) (d3)(d3)0 20V LSR (km s )0.00.20.4 T R * ( K ) (d4) (d) CS Figure 5.
Profile maps of the outflows of Mon R2. The description of each map is the same as that in Figure 3. The blue starat the center is IRAS 06035-0622, and that in the southeast is IRAS 06056-0621.
The CO bipolar outflow of G090.21+02.32 was first detected by Clark (1986) (which is near the dark cloud L988a).However, there is strong emission in the blue wing at the peak of the blue lobe in Clark (1986) (see panel (a4) ofFigure 7), but this emission cannot be the blue lobe of the CO outflow. Instead, we suggest that G090.21+02.32only possesses a red lobe rather than a bipolar CO outflows.We also detected CO, HCO + , and CS outflows for the first time for this source. There are multi-velocity componentsat ∼ − in the CS and CO line profiles. Therefore, we considered that there might be two features along theline of sight (see panel (e) of Figure 1), and G090.21+02.32 only has red lobes of CO, HCO + and CS. The emissionintensities of HCO + and CS of this source, especially the red lobes of the outflows, are weak.IRAS 21007+4951 is located near the outflow, which is associated with the H O maser, UC H II and WISE emission(Xu et al. 2013; Wood & Churchwell 1989). All of these dense tracers indicate that the IRAS source might be apossible excitation source of the outflows. 3.2.6. G105.41+09.87
G105.41+09.87 is near the open cluster NGC 7129 (Trinidad et al. 2004), and this region is extremely complex. Itincludes two far-infrared sources (i.e., NGC 7129 FIRS1 and NGC 7129 FIRS2, Bechis et al. 1978) and two Herbig-Haro objects (i.e., HH 103 and HH 105 Edwards & Snell 1983). Fuente et al. (2001) detected multiple CO outflowsin this region. We also detected three CO bipolar outflows, where two are located close to the edge of the figure andthe other one is located at the center (see panel (a1) of Figure 8). In this work, we have mainly analyzed the outflowsat the center. utflows in nine sources
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 0 200.00.51.0 T R * ( K ) (a3)a(3)0 20V LSR (km s )01020 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 0 10 20V LSR (km s )01 T R * ( K ) e(4)b(4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 0 2002 T R * ( K ) (c3) 0 20V LSR (km s )024 T R * ( K ) (c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 0 2002 T R * ( K ) (d3)0 20V LSR (km s )024 T R * ( K ) (d4) (d) CS Figure 6.
Profile maps of the outflow in NGC2264. The contour levels of the CO outflow are from 20% to 90% of the peakintensity of each outflow lobe. The blue star at the center is IRAS 06384+0932, and that at the south is IRAS 06384+0929.The description of each map is the same as that in Figure 3
The CO, HCO + and CS outflows were detected for the first time. We detect HCO + , CO and CS bipolar outflowsin this region. Similar to the CO outflow, we mainly analyzed the bipolar outflow at the center. The CO outflow ofG105.41+09.87 is extended, while the CO, HCO + and CS outflows are more concentrated, especially the CS outflows(see Figure 8).There are two emission peaks of C O in this region. One is located at the center, which is associated with theIRAS source (IRAS 21418+6552) and the WISE emission, and the other one is located in the south. An H O maser isassociated with the IRAS source (Xu et al. 2013), so the outflow in the center might be associated with it. Meanwhile,the emission of C O in the south might be associated with the outflow in the south.3.2.7.
IRAS 22198+6336
IRAS 22198+6336 is located near the dark cloud L1204A. The CO bipolar outflows of the source was first studiedby Fukui (1989), although detailed description was not provided. Thus, our work is the first to provide a detaileddescription of the outflows of this source. IRAS 22198+6336 presents not bipolar, but multiple CO outflows (seepanel (a1) of Figure 9), where the two red lobes are aligned the northwest–southeast direction, and the two blue lobesare aligned the northeast–southwest direction. Meanwhile, these blue and red lobes intersect. As both the red andblue lobes have two peaks, we infer that there are probably two pairs of bipolar outflows in this region. The southernone is along the northeast–southwest direction, and the northern one is along the east–west direction.4
Liu et al.
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 25 0 2505 T R * ( K ) (a3)25 0 25V LSR (km s )0.02.55.0 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 024 T R * ( K ) (b3)20 0 20V LSR (km s )02 T R * ( K ) (b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 10 0 10V LSR (km s )0.00.5 T R * ( K ) c(4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 10 0 10V LSR (km s )0.00.5 T R * ( K ) d(4) (d) CS Figure 7.
Profile maps of the outflows in G090.21+02.32. Panel (a4) shows the CO spectrum at the position which is markedby the endpoint of the straight purple line in (a1), and the position is the peak position of the blue emission found by Clark(1986). Panels (b1–b4) are similar to panels (a1–a4), while the spectrum is from CO. The description of each map is the sameas that in Figure 3.
We also detected HCO + and CS bipolar outflows in this region, as well as the blue lobe of an CO outflow. However,different to the structures seen in the CO outflows, both the HCO + and CS outflows seem to have one pair of bipolaroutflow. The blue lobes of the HCO + and CS outflows are more concentrated than that of the CO outflows. Althoughthe red lobes of the HCO + and CS outflows are extended and their structures are different from those of the COoutflows, they only have one emission peak. As the brightness temperatures of HCO + and CS are relatively lowerthan those of the other sources, the outflow maps of HCO + and CS are weak.IRAS 22198+6336 is located at the center of the bipolar outflows, and the WISE emission is also near the IRASsource. Hence, IRAS 22198+6336 might be the excitation source of the outflows.3.2.8. L1206
Only the blue lobe of the CO outflow was detected in L1206 by Sugitani et al. (1989); Xu et al. (2006b), whileBeltr´an et al. (2006) and Liu et al. (2020) successfully detected the blue and red lobes of the CO outflow. Wealso detected a pair of bipolar outflow of this source. Hence, there is a pair of bipolar CO outflows in L1206 (seedetails in panel (a1) of Figure 10). Apart from CO, we detected bipolar CO, HCO + , and CS outflows from thissource. The structures of these four groups of outflows are similar, i.e., the extended red lobes are located to thenorthwest and the compact blue lobes are located at the center. In general, the bipolar outflows are aligned along thenorthwest–southeast direction. Except for the CS outflow, the red lobes of the CO, CO, and HCO + outflows are utflows in nine sources
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 20 002 T R * ( K ) (a3)a(3) 20 0V LSR (km s )010 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 0.02.55.0 T R * ( K ) (b3)20 10 0V LSR (km s )05 T R * ( K ) (b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 25 0 250.00.20.4 T R * ( K ) (c3)(c3)25 0 25V LSR (km s )0.00.20.4 T R * ( K ) (c4)(c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 20 00.00.20.4 T R * ( K ) (d3)(d3) 20 0V LSR (km s )0.00.20.4 T R * ( K ) (d4) (d) CS Figure 8.
Profile maps of the outflows in G105.41+09.87. The blue star at the center is IRAS 21418+6552, and the contourlevels of the CO outflow are from 10% to 90% of the peak intensity of each outflow lobe. The other descriptions of each mapare the same as those in Figure 3. complex, where the different components seen in the red lobes are difficult to be separated with each other under thepresent resolution.There are two IRAS sources in this region (i.e., IRAS 22272+6358A and IRAS 22272+6358B). IRAS 22272+6358Ais located near the center of the bipolar outflows. Meanwhile, there is WISE emission with red color, which impliesan earlier object relative to the eastern yellow-green one. The emission peak of C O is also near IRAS 22272+6358Aand the red WISE emission. Therefore, IRAS 22272+6358A might be the source of excitation of the outflows.3.2.9.
Cep A
We have detected CO, CO, HCO + , and CS outflows from this source (see Figure 11). The configurations of the CO bipolar outflow (see panel (a1) Figure 11) is similar to the results of Rodriguez et al. (1980); Ho et al. (1982);Narayanan & Walker (1996); Xu et al. (2006b). The velocity ranges of the CO outflows have been extended from −
36 km s − to −
42 km s − in the blue lobe, and from 14 km s − to 33 km s − in the red lobe (Rodriguez et al. 1980).After updating the velocity ranges, the structures of the outflows are also similar to the morphologies detected by Hoet al. (1982); Xu et al. (2006b).The red lobes of the CO, CO, and HCO + outflows appear to have two peaks. For the CS outflow, there areeven three components in the red lobe. The sizes of the blue lobes are similar for the four groups of outflows, but theydiffer greatly from those of the corresponding red lobes. The red lobes of the CO and CS outflows are significantly6
Liu et al.
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 25 0024 T R * ( K ) (a3)(a3) 25 0V LSR (km s )012 T R * ( K ) (a4)(a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 20 10 0V LSR (km s )01 T R * ( K ) e(3)(b3) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 20 00.00.20.4 T R * ( K ) (c3)(c3) 20 0V LSR (km s )0.00.20.4 T R * ( K ) (c4)(c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 0.00.20.4 T R * ( K ) (d3)(d3)20 10 0V LSR (km s )0.00.20.4 T R * ( K ) (d4) (d) CS Figure 9.
Profile maps of the outflows in IRAS 22198+6336. The description of each map is the same as that in Figure 3.The blue star is IRAS 22198+6336, and the contour levels of the CS outflow are from 40% to 90% of the peak intensity of eachoutflow lobe. more extended than those of CO and HCO + . Different to the other outflows, the CO outflow has an additionalred lobe in the east.There are three IRAS sources (IRAS 22543+6145, IRAS 22540+6146, and IRAS 22544+6141) in this region. IRAS22543+6143, near the white region with strong WISE emission, is located at the center of the bipolar outflows (seeFigure 11), which indicates that IRAS 22543+6413 is a possible excitation source of the outflows. utflows in nine sources
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 02 T R * ( K ) (a3)(a3) 20 0V LSR (km s )02 T R * ( K ) (a4)(a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 05 T R * ( K ) (b3)20 10 0V LSR (km s )05 T R * ( K ) (b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 20 00.00.2 T R * ( K ) (c3)(c3) 20 0V LSR (km s )0.00.2 T R * ( K ) (c4)(c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 0.00.20.4 T R * ( K ) (d3)(d3)20 10 0V LSR (km s )0.00.5 T R * ( K ) (d4) (d) CS Figure 10.
Profile maps of the outflows in L1206. The description of each map is the same as that in Figure 3. The blue starat the center is IRAS 22272+6358A, and that in the east is IRAS 22272+6358B. Liu et al.
505 (a1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (a2) 50 001020 T R * ( K ) (a3)50 0V LSR (km s )01020 T R * ( K ) (a4) (a) CO
505 (b1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (b2) 25 005 T R * ( K ) (b3) 25 0V LSR (km s )05 T R * ( K ) (b4) (b) CO
505 (c1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (c2) 50 0024 T R * ( K ) (c3)50 0V LSR (km s )024 T R * ( K ) (c4) (c) HCO +
505 (d1) 505 R.A. (arcmin)505 D e c l . ( a r c m i n ) (d2) 024 T R * ( K ) (d3) 20 0V LSR (km s )012 T R * ( K ) (d4) (d) CS Figure 11.
Profile maps of the outflows in Cep A. The description of each map is the same as that in Figure 3. The bluestar at the center is IRAS 22543+6145, while that in the southeast is IRAS 22544+6141, and that in the northwest is IRAS22540+6146. utflows in nine sources T a b l e . P h y s i c a l p r o p e r t i e s o f t h e C O o u t fl o w s . S o u r ce I nd e x L o b e N M l o b e (cid:104) ∆ v l o b e (cid:105) l l o b e P l o b e E l o b e t l o b e L m ( l o b e ) ( c m − )( M (cid:12) )( k m s − )( p c )( M (cid:12) k m s − )( e r g )( y r )( − L (cid:12) ) ( )( )( )( )( )( )( )( )( )( )( ) L b l u e . . . . . . . . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . M o n R b l u e . . . . . . . . r e d . . . . . . . . N G C b l u e . . . . . . . . r e d . . . . . . . . G . + . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . I R A S + b l u e . . . . . . . . ........................... r e d . . . . . . . . L b l u e . . . . . . . . r e d . . . . . . . . C e p A b l u e . . . . . . . . r e d . . . . . . . . ........................... S t a t i s t i c m i n . . . . . . . . m a x . . . . . . . . m e a n . . . . . . . . m e d i a n . . . . . . . . T a b l e c o n t i n u e do nn e x t pa ge Liu et al. T a b l e ( c o n t i n u e d ) S o u r ce I nd e x L o b e N M l o b e (cid:104) ∆ v l o b e (cid:105) l l o b e P l o b e E l o b e t l o b e L m ( l o b e ) ( c m − )( M (cid:12) )( k m s − )( p c )( M (cid:12) k m s − )( e r g )( y r )( − L (cid:12) ) ( )( )( )( )( )( )( )( )( )( )( ) N o t e — ( ) S o u r ce n a m e . ( ) I nd e x . T h e i nd e x o f t h e o u t fl o w l o b e o f e a c h s o u r ce i s un i q u e , a nd a v a c a n t i nd e x c o rr e s p o nd s t oa n o u t fl o w o f o t h e r m o l ec u l e s . ( ) R e d / b l u e l o b e . ( ) H d e n s i t y o f t h e r e d / b l u e l o b e . ( ) M a ss o f t h e r e d / b l u e l o b e . ( ) V e l o c i t y o f t h e r e d / b l u e l o b e . ( ) L e n g t h o f t h e r e d / b l u e l o b e . ( ) M o m e n t u m o f t h e r e d / b l u e l o b e . ( ) K i n e t i ce n e r g y o f t h e r e d / b l u e l o b e . ( ) D y n a m i c a l t i m e s c a l e o f t h e r e d / b l u e l o b e . ( ) M ec h a n i c a l l u m i n o s i t y o f t h e r e d / b l u e l o b e . T h e l a s t f o u r li n e s a r e t h e m e a n , m e d i a n , m i n , a nd m a xv a l u e s o f t h e s e p a r a m e t e r s . utflows in nine sources T a b l e . P h y s i c a l p r o t e r t i e s o f t h e C O o u t fl o w s . S o u r ce I nd e x l o b e N M l o b e (cid:104) ∆ v l o b e (cid:105) l l o b e P l o b e E l o b e t l o b e L m ( l o b e ) ( c m − )( M (cid:12) )( k m s − )( p c )( M (cid:12) k m s − )( e r g )( y r )( − L (cid:12) ) ( )( )( )( )( )( )( )( )( )( )( ) L b l u e . . . . . . . . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . M o n R b l u e . . . . . . . . r e d . . . . . . . . N G C ........................... r e d . . . . . . . . G . + . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . I R A S + b l u e . . . . . . . . b l u e . . . . . . . . ........................... L b l u e . . . . . . . . r e d . . . . . . . . C e p A b l u e . . . . . . . . r e d . . . . . . . . r e d . . . . . . . . S t a t i s t i c m i n . . . . . . . . m a x . . . . . . . . m e a n . . . . . . . . m e d i a n . . . . . . . . N o t e — T h e d e s c r i p t i o n o f e a c h c o l u m n i s t h e s a m e a s t h a t o f T a b l e . Liu et al. T a b l e . P h y s i c a l p r o p e r t i e s o f t h e H C O + o u t fl o w s . S o u r ce I nd e x l o b e N M l o b e (cid:104) ∆ v l o b e (cid:105) l l o b e P l o b e E l o b e t l o b e L m ( l o b e ) ( c m − )( M (cid:12) )( k m s − )( p c )( M (cid:12) k m s − )( e r g )( y r )( L (cid:12) ) ( )( )( )( )( )( )( )( )( )( )( ) L b l u e . . . . . . . . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . M o n R b l u e . . . . . . . . r e d . . . . . . . . N G C b l u e . . . . . . . . r e d . . . . . . . . G . + . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . I R A S + b l u e . . . . . . . . ........................... r e d . . . . . . . . L b l u e . . . . . . . . r e d . . . . . . . . C e p A b l u e . . . . . . . . r e d . . . . . . . . r e d . . . . . . . . S t a t i s t i c m i n . . . . . . . . m a x . . . . . . . . m e a n . . . . . . . . m e d i a n . . . . . . . . N o t e — T h e d e s c r i p t i o n o f e a c h c o l u m n i s t h e s a m e a s t h a t o f T a b l e . utflows in nine sources T a b l e . P h y s i c a l p r o p e r t i e s o f t h e C S o u t fl o w s . S o u r ce I nd e x L o b e N M l o b e (cid:104) ∆ v l o b e (cid:105) l l o b e P ( l o b e ) E ( l o b e ) t l o b e L m ( l o b e ) ( c m − )( M (cid:12) )( k m s − )( p c )( M (cid:12) k m s − )( e r g )( y r )( − L (cid:12) ) ( )( )( )( )( )( )( )( )( )( )( ) L b l u e . . . . . . . . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . M o n R b l u e . . . . . . . . r e d . . . . . . . . N G C b l u e . . . . . . . . r e d . . . . . . . . G . + . r e d . . . . . . . . G . + . b l u e . . . . . . . . r e d . . . . . . . . I R A S + b l u e . . . . . . . . ........................... r e d . . . . . . . . L b l u e . . . . . . . . r e d . . . . . . . . C e p A b l u e . . . . . . . . r e d . . . . . . . . r e d . . . . . . . . S t a t i s t i c m i n . . . . . . . . m a x . . . . . . . . m e a n . . . . . . . . m e d i a n . . . . . . . . N o t e — T h e d e s c r i p t i o n o f e a c h c o l u m n i s t h e s a m e a s t h a t o f T a b l e . Liu et al. M ( M ) (a) Masses P ( M k m s ) (b) Momenta t ( y r ) (c) Dynamical timescales E ( e r g ) (d) Kinetic energies L m ( L ) (e) Mechanical luminosities L e n g t h ( p c ) (f) Lengths V l o b e ( k m s ) (g) Velocities CO COHCO + CS CO COHCO + CS (h) Legend Figure 12.
The distributions of the physical properties of the outflows. The dashed lines are the mean value of the physicalproperties. The meaning of each index is given in Tables 6 – 9. utflows in nine sources
Physical properties of the outflows
Due to the accurate distances of these nearby sources and the high-sensitivity observations, we have obtained moreaccurate physical properties than found previously for these objects. The lengths, masses, momenta, kinetic energies,mechanical luminosities, and dynamical timescales were calculated (see Appendix A). The physical quantities of thesemolecular lines are summarized in Tables 6 – 9, and the distributions of these quantities are displayed in Figure 12.For CO, CO, and CS, the molecular outflow of each lobe has a typical momentum of a few 10 M (cid:12) km s − , akinetic energy of a few 10 erg, a dynamical timescale of a few 10 yr, and a mechanical luminosity of a few 10 − L (cid:12) .However, the momenta, kinetic energies and mechanical luminosities of the HCO + outflows are an order of magnitudelarger than those of CO, CO and CS. The typical outflow mass for CO and HCO + is a few 10 M (cid:12) km s − ,which is an order magnitude larger than CO and CS. Although the masses of CO outflow is silimar to HCO + , themomenta, kinetic energies and mechanical luminosities of CO are lower than those of HCO + . It might result fromthe outflow velocity for HCO + is much larger than CO. However, there is no order of magnitude difference in thedynamical timescales of these four kinds of outflows.We also obtained more accurate outflow velocities ( (cid:104) ∆ v (cid:105) ) than previously found, where our results show that (cid:104) ∆ v (cid:105) ( CO) ≈ (cid:104) ∆ v (cid:105) (HCO + ) > (cid:104) ∆ v (cid:105) (CS) ≈ (cid:104) ∆ v (cid:105) ( CO). This relationship might indicate that relatively high-velocityoutflows can be traced by CO and HCO + , and relatively low-velocity outflows can be traced by CO and CS. In oursurvey, the typical dynamical timescales ( t ) of our samples are lower than those found by Beuther et al. (2002); Zhanget al. (2005). Meanwhile, the results show that t CO ≈ t CS > t CO ≈ t HCO + . Considering that different gases tracedifferent parts of the molecular clouds, the results seem to indicate that the inner gas (traced by CO and CS) flowsrelatively slower than the outer gas (traced by CO and HCO + ). Meanwhile, the outer gas might disperse earlierthan the inner gas. However, due to the limited number of objects in our sample (i.e., only nine sources), a largersample size is needed to confirm/refute this tentative conclusion.3.4. Correlations between the outflow mass, mechanical luminosity and bolometric luminosity of the central sources
A positive correlation was found between the masses ( M ) of the outflows and the bolometric luminosities ( L bol ) ofthe central IRAS sources (see Eq. B9 and Figure 13), where the slope of the best-fitting line is similar to that foundby Wu et al. (2004); Maud et al. (2015). This correlation suggests that the mass of an outflow probably depends onthe nature of the central source (Bally & Lada 1983; Wu et al. 2004; Maud et al. 2015). Furthermore, the effect of thecentral star on the surrounding gas seems to increase from the inside out, because the slope of the best-fitting line ofthe molecules tracing the outer gas is greater than that tracing the inner gas.Similar to the results of Bontemps et al. (1996); Churchwell (1997); Wu et al. (2004); Maud et al. (2015), we also findthat the mechanical force ( F = P/ (cid:104) ∆ v (cid:105) ), the mass rate of the outflow ( ˙ M = M/t ), and mechanical luminosity ( L m )correlate with the bolometric luminosity of the central IRAS source (see details in Eqs. B10 – B12, and Figures 15 –16), where the power-law indices of the best-fitting lines among those physical properties are similar to those foundby Wu et al. (2004) and Maud et al. (2015). In addition, these relationships also imply that the bolometric luminosityof the central IRAS sources and mechanical luminosity of the outflow are probably correlated with the other physicalproperties (e.g., the accretion rate). Hence, we suggest the following dependencies: bolometric luminosity → accretionrate → mass-loss rate in the outflow → mechanical luminosity of outflow (see also Wu et al. 2004). Indeed, we findthat the mass-loss rates in the outflows are correlated with the mechanical luminosities of the outflows (see Eq. B13and Figure 17). This dependency was also found by Maud et al. (2015), who had indicated that the central sourcewith higher bolometric luminosity might entrain more material and thus can drive more powerful and more energeticoutflow. SUMMARYWe searched for outflows using multi-molecular lines toward nine nearby HMSFRs with accurate distances with the14-m PMODLH millimeter-wavelength telescope. The main results of our study are summarized as follows:1. CO, CO , HCO + , and CS outflows were detected toward all nine sources (i.e., the detection rate of all outflowswas 100%). Bipolar or multiple outflows of CO, HCO + , and CS were detected for eight sources (i.e., the detectionrate was about 89%). Bipolar outflows of CO were detected for six sources (i.e., the detection rate was about 67%).2. The full line widths of different molecules may have the following relationship: ∆ V CO > ∆ V HCO + > ∆ V CS ≈ ∆ V CO > ∆ V CO .6 Liu et al. CO and HCO + can be used to trace relatively high-velocity outflows, and CO and CS can be used to tracerelatively low-velocity outflows.4. The dynamical timescale of different molecules may have the following relationship: t CO ≈ t CS > t CO ≈ t HCO + .5. There was a strong correlation between the bolometric luminosity of the central IRAS source and the mechanicalluminosities of the outflows (including CO, CO, HCO + and CS), and between the bolometric luminosities andoutflow masses. The former correlation suggests a flow dependence, i.e., bolometric luminosity → accretion rate → mass-loss rate in the outflow → mechanical luminosity of outflow. The latter relationship indicates that the mass ofthe outflow probably depends on its driving source.ACKNOWLEDGMENTSWe are grateful to all the staff of Purple Mountain Observatory Delingha, especially our observer colleagues forobtaining the excellent observations. We would like to thank the anonymous referee. This work was funded by theNSFC, under grant numbers 11933011, 11873019, and 11673066, and by the Key Laboratory for Radio Astronomy.The research work was also supported by the National Natural Science Fund Committee of the Chinese Academy ofSciences Astronomical Union Funds No. U1731124, U2031202.APPENDIX A. DERIVING THE OUTFLOW PARAMETERSThe H column density, N (H ), traced by CO is given as Snell et al. (1984) N (H ) = 4 . × T ex e − . /T ex (cid:90) T mb dv. (A1)where the velocity range to be integrated is that of the wing range. In this equation we assume that the gas isin local thermodynamic equilibrium (LTE), X ( CO) = [ CO] / [H ] = 10 − (Snell et al. 1984), and the excitationtemperature, T ex , is 30 K.The H column density, N (H ), traced by CO is Wilson et al. (2013) N (H ) = 2 . × T ex e − . /T ex (cid:90) T mb dv (A2)where the velocity range to be integrated is that of the line’s wings. In this equation we assume that the gas is inLTE, X ( CO) = [ CO] / [H ] = 2 × − , and T ex = 30 K (Li et al. 2016).The H column density, N (H ), traced by HCO + can be found as Yang et al. (1991) N (H ) = 1 . × T ex − e − . /T ex (cid:90) T mb dv. (A3)where the integration range is over the range of the wings. In this equation we assume that the gas is in LTE, X (HCO + ) = [HCO + ] / [H ] = 10 − (Turner et al. 1997) and T ex = 15 K.The H column density, N (H ), traced by CS is N (H ) = 3 × k T ex π µ d hve − hv/k T ex (cid:90) T mb dv (A4)where k is the Boltzmann constant (1 . × − erg K − ), h is the Planck constant (6 . × − erg s), µ d is thedipole moment (1.96 D), and v is the transition frequency (97.981 GHz). The velocity range of integration is that ofthe wing’s range. In this equation we assume that the gas is in LTE, X (CS) = [CS] / [H ] = 10 − , and T ex = 20 K(Tatematsu et al. 1998).The mass of the outflow lobe, M lobe , can be found as: M lobe = N lobe A lobe µm H (A5) utflows in nine sources A lobe represents the area of the blue/red lobes of outflows, µ = 2 .
72 is the mean molecular weight, and m H is the hydrogen molecule (Garden et al. 1991). The area was estimated by the region covered by 50% of the outflowpeak.The momentum ( P lobe ) and kinetic energy ( E lobe ) of an outflow lobe are, respectively: P lobe = (cid:88) A lobe M lobe (cid:104) ∆ v lobe (cid:105) , (A6)and E lobe = 12 (cid:88) A lobe M lobe (cid:104) ∆ v (cid:105) . (A7)where (cid:104) ∆ v lobe (cid:105) and (cid:104) ∆ v (cid:105) are the velocity (i.e., the relative velocity with respect to the central velocity), and thesquare of the velocity of an outflow lobe (see detail in Li et al. 2018). The mechanical luminosity ( L lobe ) of an outflowlobe is L lobe = E lobe /t lobe (A8)where t lobe = l lobe / ∆ v max , ∆ v max is the maximum outflow lobe velocity, and l lobe is the length of the outflow.As it is hard to determine the inclination angle of an outflow, we have adopted a mean inclination angle of 57 . ◦ to conform with similar studies (Bontemps et al. 1996). The inclination and blending correction factors are cited (Liet al. 2019, see table 5 of that paper). B. RELATIONSHIP BETWEEN THE OUTFLOW MASS, MECHANICAL LUMINOSITY AND BOLOMETRICLUMINOSITY OF THE CENTRAL SOURCESThe mass, M , of the CO, CO, HCO + , and CS outflows as a function of the bolometric luminosity, L bol , of thecentral IRAS source is as follows (see Figure 13):log M ( CO) = (0 . ± .
17) log L bol + ( − . ± . , r = 0 .
57; (B9a)log M ( CO) = (0 . ± .
07) log L bol + ( − . ± . , r = 0 .
85; (B9b)log M (HCO + ) = (0 . ± .
09) log L bol + ( − . ± . , r = 0 .
82; (B9c)log M (CS) = (0 . ± .
14) log L bol + ( − . ± . , r = 0 . . (B9d)The mass outflow rate, ˙ M , of the CO, CO, HCO + , and CS outflows as a function of the bolometric luminosity, L bol , of the central IRAS source is as follows (see Figure 14):log ˙ M ( CO) = (0 . ± .
19) log L bol + ( − . ± . , r = 0 .
60; (B10a)log ˙ M ( CO) = (0 . ± .
07) log L bol + ( − . ± . , r = 0 .
87; (B10b)log ˙ M (HCO + ) = (0 . ± .
13) log L bol + ( − . ± . , r = 0 .
78; (B10c)log ˙ M (CS) = (0 . ± .
17) log L bol + ( − . ± . , r = 0 . . (B10d)The outflow force, F , of the CO, CO, HCO + , and CS outflows as a function of the bolometric luminosity, L bol ,of the central IRAS source is as follows (see Figure 15):log F ( CO) = (0 . ± .
21) log L bol + ( − . ± . , r = 0 .
61; (B11a)log F ( CO) = (0 . ± .
10) log L bol + ( − . ± . , r = 0 .
86; (B11b)log F (HCO + ) = (0 . ± .
17) log L bol + ( − . ± . , r = 0 .
76; (B11c)log F (CS) = (0 . ± .
19) log L bol + ( − . ± . , r = 0 . . (B11d)The mechanical luminosity, L m , of the CO, CO, HCO + , and CS outflows as a function of the bolometricluminosity, L bol , of the central IRAS source is as follows (see Figure 16):8 Liu et al. log L m ( CO) = (0 . ± .
24) log L bol + ( − . ± . , r = 0 .
61; (B12a)log L m ( CO) = (0 . ± .
14) log L bol + ( − . ± . , r = 0 .
81; (B12b)log L m (HCO + ) = (0 . ± .
23) log L bol + ( − . ± . , r = 0 .
73; (B12c)log L m (CS) = (0 . ± .
23) log L bol + ( − . ± . , r = 0 . . (B12d)The mass outflow rate, ˙ M , of the CO, CO, HCO + , and CS outflows as a function of the mechanical luminosity, L m , of the outflows is as follows (see Figure 17):log ˙ M ( CO) = (0 . ± .
07) log L m + ( − . ± . , r = 0 .
93; (B13a)log ˙ M ( CO) = (0 . ± .
05) log L m + ( − . ± . , r = 0 .
94; (B13b)log ˙ M (HCO + ) = (0 . ± .
05) log L m + ( − . ± . , r = 0 .
94; (B13c)log ˙ M (CS) = (0 . ± .
06) log L m + ( − . ± . , r = 0 . . (B13d) utflows in nine sources L bol ( L )10 M ( M ) (a) CO L bol ( L )10 M ( M ) (b) CO L bol ( L )10 M ( M ) (c) HCO + L bol ( L )10 M ( M ) (d) CS L bol ( L )10 M ( M ) CO COHCO + CS (e) Fitting lines Figure 13.
The mass ( M ) of different molecular outflows as a function of the bolometric luminosity ( L bol ) of the central IRASsource. Each molecular line is given at the bottom of each panel. Panel (e) is the least-square fitting lines of the four molecularoutflows. Liu et al. L bol ( L )10 O u t f l o w R a t e ( M y r ) (a) CO L bol ( L )10 O u t f l o w R a t e ( M y r ) (b) CO L bol ( L )10 O u t f l o w R a t e ( M y r ) (c) HCO + L bol ( L )10 O u t f l o w R a t e ( M y r ) (d) CS L bol ( L )10 O u t f l o w R a t e ( M y r ) CO COHCO + CS (e) Fitting lines Figure 14.
The mass outflow rate ( ˙ M ) of different molecular outflows as a function of the bolometric luminosity ( L bol ) of thecentral IRAS source. Each molecular line is indicated at the bottom of each panel. Panel (e) is the least-square fitting lines ofthe four molecular outflows. utflows in nine sources L bol ( L )10 F ( M k m s y r ) (a) CO L bol ( L )10 F ( M k m s y r ) (b) CO L bol ( L )10 F ( M k m s y r ) (c) HCO + L bol ( L )10 F ( M k m s y r ) (d) CS L bol ( L )10 F ( M k m s y r ) CO COHCO + CS (e) Fitting lines Figure 15.
The outflow force ( F ) of the different molecular outflows as a function of the bolometric luminosity ( L bol ) of eachcentral IRAS source. The molecular line is given at the bottom of each panel. Panel (e) is the least-square fitting lines of thefour molecular outflows. Liu et al. L bol ( L )10 L m ( L ) (a) CO L bol ( L )10 L m ( L ) (b) CO L bol ( L )10 L m ( L ) (c) HCO + L bol ( L )10 L m ( L ) (d) CS L bol ( L )10 L m ( L ) CO COHCO + CS (e) Fitting lines Figure 16.
The mechanical luminosity ( L m ) of the different molecular outflows as a function of the bolometric luminosity( L bol ) of the central IRAS source. The molecular line is given at the bottom of each panel. Panel (e) is the least-square fittinglines of the four molecular outflows. utflows in nine sources L m ( L )10 O u t f l o w R a t e ( M y r ) (a) CO L m ( L )10 O u t f l o w R a t e ( M y r ) (b) CO L m ( L )10 O u t f l o w R a t e ( M y r ) (c) HCO + L m ( L )10 O u t f l o w R a t e ( M y r ) (d) CS L m ( L )10 O u t f l o w R a t e ( M y r ) CO COHCO + CS (e) Fitting lines Figure 17.
The outflow rate ( ˙ M ) of the different molecular outflows as a function of the mechanical luminosity ( L m ) of outflow.The molecular transition is given at the bottom of each panel. Panel (e) is the least-square fitting lines of the four molecularoutflows. Liu et al.
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