Optical Spectrum

Additionally, we observed V883 Ori on the night of 29 February, 2016 with the Magellan Inamori Kyocera Echelle (MIKE, Bernstein et al., 2003), a double echelle spectrograph at the Magellan (Clay) 6.5 m telescope, located in Las Campanas, Chile. This high resolution spectrograph covers a full optical wave- length range in the blue (320-480 nm) and the red (440-1000 nm) regime with spectral resolutions of 25000 and 19000, respectively. Our observations were taken with a slit size of 0.7×500 and the data have been binned 2×2 in a slow readout mode with an exposure time of 1860 s. During the observation run

Figure 4.3: 12_{CO intensity maps (moment-0) integrated over the velocity range}

of 0.75 − 8.0 km s−1. Black contours show the continuum emission around V883 Ori at 10, 30, 80, 150 and 250 × rms (0.25 mJy beam−1_{). The upper}

right inset is a closeup (± 1.8”) of the central object. The 0.3500×0.2700 with P.A. = -90◦ synthesised beam is shown on the lower left corner.

were taken: Milky flats, Quartz flats, Twilight flats, ThAr comparison lamps and bias frames to use in the data reduction process. Thus, the data were bias-subtracted and flat-fielded to correct pixel to pixel variations by using the Carnegie Python tools3 _{(CarPy; Kelson, 2003).}

4.3

Results

We obtained emission line profile data from V883 Ori of isotopologues 12_CO, 13_{CO and C}18_{O with transitions J = 2→1 to trace the different components of}

this FUor object. Figure 4.1 is a cartoon of the components detected with these optically thick and thin emissions, with a systemic velocity of 4.3 km s−1 _(Cieza

et al., 2016). The CO emissions with bipolar shaped lobes, symmetrically placed around the central object (V883 Ori) are the product of the direct interaction between young outflows and the surrounding envelope, where the molecular outflows entrain part of the gas along the outflow axis independent of the physical origin. Then, from12_{CO and}13_{CO emissions a bipolar shape is}

probed, where the cavity traced by the 12_{CO and pointing towards us, is less}

embedded in the surrounding envelope, while the cavity traced by the 13_CO

is more embedded than its counterpart. Unfortunately, we could not rule out faster gas towards the outflow axis from this data set or previous observations in databases. The colder and denser material close to the central object is traced by the13_{CO and C}18_{O isotopes, where a disk with a Keplerian rotational profile}

is probed by the C18_{O emission. For simplicity throughout the text, the blue-}

and red-shifted12_{CO and}13_{CO emissions probing the bipolar cone are referred}

to as the southern and northern cavities, respectively. In order to estimate the outflow position angle (PA), we drew a line along the velocity gradient observed in C18O and through the 1.3 mm continuum and thus, we obtained a PA of

∼ 120◦ north through east 4. From the 1.3 mm continuum emission, Cieza et al. (2016) found a position angle of ∼ 32.4◦ and from the major and minor

axes of this emission an inclination (i) of∼ 38.3◦±1.0. Here, we adopted this inclination value to describe the orientation of the outflows.

4.3.1

CO Emission

Figure 4.2a presents the integrated intensity of the weighted velocity (moment- 1) maps of V883 Ori. This moment is integrated over the narrow velocity range with respect to the Local Standard of Rest (LSR) of 2.0 −6.25 km s−1, where the emission is detected at levels higher than 3σ (σ = 1.5×10−2 Jy beam−1_{). This integration range for} 12_{CO is chosen to match the moment-1}

of 13_{CO and to display the kinematic structure of the} 12_{CO and} 13_{CO line}

emission, see Section 4.3.2. The12_{CO emission tracing the southern molecular}

outflow has a range between ∼ 0.75 km s−1 _{and ∼4.25 km s}−1_{, while the}

red-shifted emission is observed in the range between 4.5 and 8.0 km s−1_{. The}

former emission is bright and extends up to the systemic velocity, which clearly traces the shape of the southern cavity. The latter is detected mostly close to the central object, and at what seems to be the end of the right arm of the outflow. However, emissions at velocities of ∼ 4.5 km s−1 _{are more likely}

to correspond to the parent molecular cloud. Thus, the emission indicated with a red oval in Figure 4.2a, at a velocity of ∼ 4.5 km s−1_{, seems to be}

better explained as being dominated by ambient emission rather than from an outflow emission, see also Figure 4.4. A slab of colder and denser envelope material located in the northern region of the outflow might be blocking the

12_{CO emission, making its interpretation ambiguous because the optically thin} 13_{CO emission is brighter on this side of the object (see Section 4.3.2 for more}

with different velocity components, and in the case of V883 Ori, the narrow velocity range of this emission causes the red-shifted12_{CO emission on this side}

of the cavity to be spatially filtered out.

Figure 4.4a shows the12_{CO channel maps, with a channel width of 0.25 km s}−1_,

where the outflow cavity of a parabolic shape is more predominant at velocities of ∼ 3.25−3.50 km s−1_{. Interestingly, there is a slightly noticeable elongated}

feature towards the southeast, while in the 13CO channel maps a more pro- nounced feature is displayed in the same velocity range and location, which geometrically overlaps the 12_{CO feature, see Figure 4.4b . This feature seems}

to move further away from the central source, and could potentially be ex- plained as outflowing layers entrained by a wide-angle wind. For this matter, we further explore kinematic features in the position-velocity (PV) diagrams to identify a possible parabolic PV structure, which can be produced by a wide-angle wind model at any inclination (Shu et al., 2000; Lee et al., 2000). Unfortunately, we did not find any signature of this characteristic, however, this does not rule out a radial wind producing a molecular outflow with a wide-opening angle.

From the southern cavity emission, we estimate an apparent opening angle of the outflow following the relation:

θo = 2 tan−1

1−e−1Ro

zo

where Ro is the transverse radius or radius to the rotation axis and zo is the

Thus, an opening angle of∼150◦ is revealed beyond ∼600 au from the central source and an extension of 7300 au assuming a distance of 414±7 pc (Menten et al., 2007).

The narrow velocity range shown in the channel maps of12_{CO data at velocity}

resolution of 0.25 km s−1_{, Figure 4.4a, leads to the conclusion that the outflow}

is not as highly energetic as other FU Ori objects in a similar evolutionary stage (Class I).

A hole in the 12_{CO emission?}

In Figure 4.3, we present integrated intensity maps of the 12_{CO emission over}

the velocity range between 0.75 and 8.0 km s−1_{. Overall, this emission traces the}

southern outflow as described above,however, it also also presents a particular flux drop coincident with the central dust continuum peak. The inset of Figure 4.3 a zoomed in image of the hole, which is significantly weaker by a factor of ∼15 compared with the immediately surrounding emission. This feature is more likely due to dust absorption of the line emission and with a contrast of this magnitude, this implies that the dust continuum is considerably more optically thick than the CO emission around the central star.

4.3.2

CO and C

O Emissions

Usually, millimeter observations of12CO in star-forming environments tend to probe optically thick gas due to the high fractional abundance (χCO ≈ 10−4)

(a)12CO

(b)13CO

Figure 4.4: Channel maps of the 12CO and 13CO. LSR velocities are shown at the top-right corner of each panel with a systemic velocity of ∼4.3 km s−1_.

Black contours represent the continuum emission around V883 Ori as shown in Figure 4.2a.

thin material. Thus, 13_{CO as a medium density tracer allows us to probe a}

higher density region than the low density tracer, 12_{CO. Figure 4.2b shows}

the 13_{CO moment-1 map integrated in the velocity range between 2.0 and}

6.25 km s−1_{. The} 13_{CO gas has a bipolar distribution with respect to the}

outflow source on the northern side of V883 Ori, which covers the red-shifted velocities between 4.5 and 6.5 km s−1. This emission likely rises from the outer envelope that surrounds the protostellar core and the material interacting with the immediate surroundings of the outflow. The southern cavity (blue- shifted 13_{CO emission) is more diffuse and weaker than on the northern side.}

The southern cavity emits at velocities between 1.75 and 4.25 km s−1 _and

probes envelope material that might indicate that the outflow has been able to accelerate medium-density gas at large distances away from the central object, where the highest velocity components are observed close to the central object and ambient velocity components widen from the central source.

In figures 4.2a and 4.2b the moment-1 maps of 12CO and 13CO are shown, integrated over the same velocity range for comparison (2.0 − 6.25 km s−1_).

The physical connection between the base of the cavity-envelope system traced by the 13_{CO isotope and what seems to be envelope material traced by} 12_CO,

that reaches velocities of only 4.5 km s−1 _{, is indicated by a red oval in the} 12_{CO moment-1 map and the physical location of the} 12_{CO emission in the}

moment-1 of 13CO is indicated by a purple oval. The velocity field shows a gradual decrease in speed from the inside out. At small radii, the outflow may be entraining inner envelope material, while at large distances from the central source it widens and acquires the systemic velocity.

sion of both isotopes overlap and trace envelope-outflow material. Both, 12_CO

and 13_{CO emissions peak on the central star, where the central disc is located.}

The blue shifted 12_{CO and} 13_{CO line emission maps of V883 Ori reveal the}

low and medium density material expanding, part of which have already been noticed in optical images, since the northern outflow is not observed, such as in the I-band image shown in Figure 4.5 where only the southern outflow appears illuminated. An important implication of these emissions is that the cavity traced by the 12_{CO gas and pointing towards us, is less embedded in the sur-}

rounding envelope, while the cavity traced by the13_{CO is more embedded than}

its counterpart. This is supported by the lack of detection of the12_{CO gas and}

the bright detection of 13_{CO on the northern side of the object.}

Besides the progressive dispersion of dense molecular gas at the northern region, an infalling and rotating motion is also observed close to the central star-disk system. It can be noted in the inset of Figure 4.2b that at the base of the cavities, the 13CO gas probes a velocity gradient along the major axis of the 1.3 mm continuum, consistent with a Keplerian rotation and indicating the rotating and infalling material onto the central source. The infalling envelope near systemic velocity agrees with the rotating equatorial disc (Cieza et al., 2016), also observed with C18_{O, the lowest abundant isotope.}

The densest material in V883 Ori is traced by the observations of the C18_O

molecule, and presented in Figure 4.2c as the moment-1 map integrated over the velocity range 2.0−6.25 km s−1_{. It is evident that this velocity map shows a}

structure delineating the material rotating around central object. In addition, the shape of the C18O emission of these maps is very similar to the shape of the 13CO gas towards the base of the cavities.

Figure 4.5: Comparison of the 1.3 mm continuum, 12_{CO and} 13_{CO emissions}

(contours) and the optical I-band (0.75 µm; Ahn et al., 2012) image of V883 Ori. Blue and magenta contours show the integrated intensity of the12CO and

13_{CO lines, respectively, at 20, 40, 80, 160, 240× 3σ levels. The cyan contours}

are the continuum emission and represent the position of V883 Ori. The green contours are the I-band data at 80, 150, 300, 450 and 600× 3σ levels.

Figure 4.6: V883 Ori spectrum of the Hα line at 6563 ˚A taken with the MIKE spectrograph. On the right column, we present the Hα velocity profiles of the FUor objects V1057 Cyg, HBC 722, and FU Ori itself. Spectra taken from Lee et al. (2015).