× 10 21
cm−2 .
(5.4)The H
2
column density derived from12
CO(J=3-2) and C18
O(J=2-1) are 8.0×
1021
cm−2
and 8.5×10 21
cm−2
, respectively. We also estimated the column density using the relation derived by Frerking et al. (1982) for dust extinction from the average extinction value, AV ∼ 11.8 magnitude (see §5.3.3), of the G173.58+2.45
cloud,N
H
2 = AV × 0.94 × 10 21
cm−2 .
(5.5) The derived H2
column density from extinction is 1.3× 10 22
cm−2
. Together with values derived from CO observation, we found the H2
column densities are very consistent. Giving the size of the cloud is 0.89×0.52 pc, we have calculated the
mass based on three column densities and the total mass is∼ 230 ± 60 M ⊙
for G173.58+2.45 region.5.3.2 High-Velocity Components and Position-Velocity Anal-ysis
The G173.58+2.45 region contains noticeable high velocity CO outflows (Shep-herd & Watson, 2002, SW02 hereafter) and H
2
bow shock features (Varricatt et al., 2005, V05 hereafter). There have been found very active and complex CO outflows and multiple sources seem to be responsible for those outflows (SW02).For further investigation of gas outflows and possible interactions with ambient gas, we overlap the identified H
2
emission to the intensity map of12
CO (J=1-0)70
5:39:35.0 33.1 31.2 29.3 27.3 25.4 23.5 21.6 19.7
41:16.7
84.890 84.880 84.870 84.860 84.850 84.840 84.830
35.695
84.890 84.880 84.870 84.860 84.850 84.840 84.830
35.695
84.890 84.880 84.870 84.860 84.850 84.840 84.830
35.695
Figure 5.5 (a) Continuum subtracted H
2
emission of G173.58+2.45 region overlaid on a intensity map of12
CO(J=2-1) line from -46 km s−1
– 10 km s−1
. The con-tours were plotted from 1.22×10 −3
mJy/pixel with a gap of 0.5×10 −3
mJy/pixel.The HH objects were labeled with alphabetic numbers in red and white colors.
The H
2
bow shocks are distributed in a region with a 80′′
radius, and the lin-ear scale is∼ 0.70 parsec. (b) HH objects, radio continuum sources and velocity
components of G173.58+2.45 region. The background grey scale is the intensity map of12
CO(J=2-1) line . The yellow contours are the 3mm continuum image from OVRO. The 1σ rms is 0.2 mJy/beam and the contours were plotted from 3.5σ with spacing to be 1σ. The blue and red-dashed contours are the velocity components of -45.9 – -17.8 and -17.8 – 10.0 km s−1
, respectively. Both red and blue contours were plotted from 3σ with spacing of 1σ. The 1σ rms of red and blue components are 4.0 and 5.0 Jy/beam, respectively.Table 5.1 Fundamental parameter of CO molecule
Molecular Transition Frequency
E k
uA ul
GHz K s
−1
12
CO 2-1 230.538001 16.6 7.1× 10 −7
3-2 345.695975 33.2 2.6× 10 −6
C18
O 2-1 219.560319 15.9 6.2× 10 −7
PV-2
(b)
Jy/beam
(a)
PV-1
0 2 4 6 8
Figure 5.6 The intensity map and the position-velocity diagrams of
12
CO(J=2-1) line from -46 km s−1
– 10 km s−1
(upper panel). The green-dashed lines indicated the cuts for position-velocity diagrams. The PV diagrams of different PV cuts are shown in the rest panels. The contour levels are plotted from zero Jy/beam with a gap of 0.75 Jy/beam.emission (Fig. 5.5). H
2
bow shocks have been found by V05 previously. They are commonly found near young stellar systems, appearing in the form of Herbig-Haro (HH) objects (Reipurth & Bally, 2001). Usually, bow shocks are related to outflows from protostars. Narrow-band imaging at wavelength of the H2
(1-0)S(1) line at 2.122 µm is very useful for detecting these bow shock features. Fig. 5.5 shows that most of the HH objects are correlated with12
CO (J=1-0) emission.Parameters of the identified HH objects are listed in Table 5.2, including the cross identification by V05. A larger number of HH objects have been found in this work. The location of each HH objects are labeled on Fig. 5.5(a). Especially, the farthest HH objects, source 4, 12 and 26, were found at a distance
∼ 0.87 pc , which
have not been identified previously. Assuming the velocity of a bow shock is about 100 km s−1
(Reipurth & Bally, 2001), then the derived dynamic timescale of H2
outflows should be∼ 0.15 Myr. This value may represents an lower limit because
these H2
bow shocks are asymmetric. Fig. 5.5(b) shows the different velocity com-ponents of12
CO(J=2-1) together with HH objects and radio continuum sources of G173.58+2.45. The blue and red-dashed contours are the velocity components of -45.9 – -17.8 and -17.8 – 10.0 km s−1
, respectively. Two continuum sources are located at northwest and southeast of core region: G173.58+2.45 :MM1 and G173.58+2.45:MM2. MM1 is coincided with strong H2
emission and the driving source(s) of east-west outflows may be located in the MM1. The HH objects in around MM1 coincided with east-west outflows very well. MM2 is coincided with the brightest stellar group in this region and located at the center of CO blue and red-shift components. HH objects 7, 9 , 17, 23, 29 and 33, aligned around MM2, were identified as outflow A1, A2, B1, B2 and B3 related to the bright cluster in V05. However, we did not see strong CO emission associated in this direction.Although the overall feature of the outflow in Fig. 5.5 appears to be extended in the east-west direction, the position-velocity maps obtained with the OVRO data (Fig. 5.6) suggests that there exist multiple complex outflows. The general feature of the PV-1 (Fig. 5.6(b)) coincide with the overall outflow, such as the blue shifted gas in the east and red shifted in the west. It clearly shows that there are several outflows, probably more than two at least; for example, two black-dashed
lines in Fig. 5.6(b) shows that there are two pairs of outflows existed in east-west direction, one is at RA offset =
±10 ′′
and another is at±50 ′′
. In addition, the PV-2 (Fig. 5.6(c)) indicates that there are another two pairs of outflow in the north-south direction. The separation of these two outflow centers is∼ 20 ′′
, which is about the angular distance between MM1 and MM2. This implies that both MM1 and MM2 may be responsible for north-south outflows. As discussed in SW02 and V05, it is possible that multiple sources or binary systems are forming in this region and these non-axial ourflows (Aspin, 1998) should be the signal of this scenario.Although the multiple outflows has been discussed in the previous observations (Shepherd & Watson, 2002; Varricatt et al., 2005), yet this is the first time we see the correction between H