To be submitted to ApJS

An AST/RO Survey of CO(4-3) in ultracompact HII regions

Wilfred M. Walsh1
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-12, Cambridge, MA 02138
arXiv:astro-ph/0306075 v1 3 Jun 2003

wwalsh@cfa.harvard.edu

ABSTRACT

The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) has

been used to observe 78 of the IRAS point sources identified by Bronfman et al. (1996)
as likely ultracompact HII regions. Results for the CO J = 4 → 3 line at 461.041 GHz
are presented. The 74 sources detected are bright and in many cases compact, making
them potentially suitable as pointing calibrators for single dish submillimeter telescopes.

1. Introduction

Most star formation (SF) occurs within the giant molecular cloud phase, and of particular
interest is the behavior of the fragmented interiors of these clouds in the stages immediately before,
during and after collapse into stellar objects. Both gaseous and dust components play vital roles in
all SF models, and this paper presents submillimeter line observations of warm and dense gas near
ultracompact HII regions, the ionized gas surrounding early-type stars. To identify the youngest
stellar objects, far infrared (FIR) observations from the IRAS satellite’s near all-sky survey have
been used (Wood & Churchwell 1989) and follow-up line studies have successfully detected emission
in many (sub)millimeter lines (e.g. Bronfman et al. 1996; Snell et al. 2000; Hatchell et al. 1998).
Radio and IR continuum emission originates from ultracompact HII regions, while submillimeter
line emission may come from hot molecular cores often found adjacent to one or more ultracompact
HII regions. These objects are considered the best current tracer of ongoing SF.

An apparent problem with the understanding of ultracompact HII regions is that their dy-
namical ages appear to be so short (∼ 104 yr) that their numbers overpredict the current rate of
SF. However the expected lifetimes depend critically on the local distribution of gas and dust (cf.
Hollenbach et al. (1994); de Pree et al. (1995)), of which little is known. Recent interferometric
observations (Walsh et al. 1998; Koo et al. 1996; Kurtz et al. 1999) suggest that at least some of
the so-called ultracompact HII regions may in fact have larger sizes and predicted ages. Thus a
better understanding of the distribution and dynamics of molecular gas and dust around ultracom-
pact HII regions is required. In this paper we present results of a survey of 78 hot cores with the
Antarctic Submillimeter Telescope and Remote Observatory. This survey is toward southern (Dec.
 –2–

. −20◦ so as to be observable with AST/RO) sources in the list of Bronfman et al. (1996) with
CS(2 → 1) emission and associated IRAS luminosity and colours typical of compact HII regions.
The sources were further selected to have line profiles indicative of inward or outward motions (e.g.,
Mardones 1998) or have extended line wings which may indicate the presence of bipolar outflows.
This database is likely to be representative of the early stages of massive SF. The results of this
survey will be combined with observations of other submillimeter lines and continuum that will be
analyzed in more detail in a subsequent paper but will also be of use to the several new southern
submillimeter radiotelescopes as potential pointing and calibration sources. Published properties
of bright, compact submillimeter sources in the southern sky are extremely sparse.

The observations are described in § 2 and in § 3 the data set is presented in the form of a table
of spectral line parameters and as plots of the full spectra. Small maps of the brightest sources are
also shown.

2. Observations

The observations were performed during the austral winter season of 2002 at the Antarctic
Submillimeter Telescope and Remote Observatory (AST/RO; Stark et al. 2001), located at 2847 m
altitude in Amundsen-Scott South Pole Station. This site has very low water vapor, high atmo-
spheric stability and a thin troposphere making it exceptionally good for submillimeter observations
(Chamberlin et al. 1997; Lane 1998). AST/RO is a 1.7 m diameter, offset Gregorian telescope ca-
pable of observing at wavelengths between 200 µm and 1.3 mm (Stark et al. 1997). The receiver
used was a dual-channel SIS waveguide receiver (Walker et al. 1992; Honingh et al. 1997) for si-
multaneous 461–492 GHz and 807 GHz observations, with double-sideband noise temperatures of
320–390 K and 1050–1190 K, respectively. Telescope efficiency, ηℓ , estimated using moon scans,
skydips, and measurements of the beam edge taper, was 81% at 461–492 GHz and 71% at 807 GHz.
The 807 GHz data will be presented, along with observations in several other bands, in a subsequent
paper. Atmosphere-corrected system temperatures ranged from 700 to 4000 K at 461–492 GHz.

A beam switching mode was used, with emission-free reference positions chosen at least 20′
from regions of interest, to make a small map of points surrounding each source. These maps were
repeated as often as required to achieve suitable signal–to–noise. Emission from the CO J = 4 → 3
and CO J = 7 → 6 lines at 461.041 GHz and 806.652 GHz, (together with the [C I] 3 P1 → 3 P0 and
[C I] 3 P2 → 3 P1 lines at 492.262 GHz and 809.342 GHz), was imaged over the 78 regions with a
spacing of a half-beamwidth or less. The beam sizes (FWHM) were 103–109′′ at 461–492 GHz and
58′′ at 807 GHz (Stark et al. 2001).

Two acousto-optical spectrometers (AOSs; Schieder et al. 1989) were used as backends. The
AOSs had 1.07 MHz resolution and 0.75 GHz effective bandwidth, resulting in velocity resolution of
0.65 km s−1 at 461 GHz and 0.37 km s−1 at 807 GHz. The data were smoothed to a uniform velocity
resolution of 1 km s−1 . The high frequency observations were made with the CO J = 7 → 6 line
 –3–

in the lower sideband (LSB). Since the intermediate frequency of the AST/RO system is 1.5 GHz,
the [C I] 3 P2 → 3 P1 line appears in the upper sideband (USB) and is superposed on the observed
LSB spectrum. The local oscillator frequency was chosen so that the nominal line centers appear
separated by 100 km s−1 in the double-sideband spectra.

The standard chopper wheel calibration technique was employed, implemented at AST/RO
by way of regular (every few minutes) observations of the sky and two blackbody loads of known
temperature (Stark et al. 2001). Atmospheric transmission was monitored by regular skydips, and
known, bright sources were observed every few hours to further check calibration and pointing. At
periodic intervals and after tuning, the receivers were manually calibrated against a liquid-nitrogen-
temperature load and the two blackbody loads at ambient temperature and about 100 K. The latter
process also corrects for the dark current of the AOS optical CCDs. The intensity calibration errors
became as large as ±15% during poor weather periods.

Once taken, the data in this survey were reduced using the COMB data reduction package.
After elimination of scans deemed faulty for various instrumental or weather-related reasons (. 7%
of the total dataset), linear baselines were removed from the spectra in all species by excluding
regions where the CS J = 2 → 1 spectra of Bronfman et al. (1996) showed emission within twice
the FWHM of Gaussian fits to the CS J = 2 → 1 line. This allowed known emission to be readily
excluded from the baseline fitting procedure.

While the original intent was to make Trms as uniform as possible across all source maps, this
was not always possible. For the CO J = 4 → 3 transition, Trms in 1 km s−1 wide channels with no
spatial smoothing is on average . 0.75 K.

3. Results

AST/RO’s pointing model (Stark et al. 2001) is currently determined by observing a small
number of sources for a 24 hr period so as to obtain full coverage of the sky in azimuth. However
these sources do not cover a wide range in elevation. As the residual pointing uncertainty after
the application of the pointing model at AST/RO is between one beamwidth in the frequency used
to determine the pointing model and one arcminute, it is a major aim of this work to identify a
larger sample of compact sources, distributed over the sky, that may be used for pointing calibration.
Therefore small images of a few square arcminutes were made of the sample with half-beam spacing.
Fig. 1 displays the brightest spectrum observed in the vicinity of each source and Fig. 2 shows the
resulting images.

Table 1 lists the results of Gaussian fits to the observed lines shown in Fig. 1. The first column
is a shortened name based on the Galactic longitude, column two is the IRAS source name, columns
three and four are the equinox J2000 coordinates. Column five is the peak antenna temperature
as estimated by the Gaussian fit, with an uncertainty due to the fitting. The actual intensity
calibration error of AST/RO is generally larger (§ 2). Columns six to eight are the central velocity,
 –4–

integrated line intensity (in K km s−1 ) and FWHM of the line as estimated by the Gaussian fitting,
respectively. Fig. 1 shows that many of the line profiles can be approximately represented by a
Gaussian form, leading to a reasonable estimate of the line strength, width and central velocity.
The Gaussians, fit to a range of channels 10 km s−1 either side of the FWHM of the Bronfman et al.
(1996) Gaussian fit to the CS J = 2 → 1 line, clearly do not provide a precise model of the profiles,
and further analysis of the spectra should refer to the original data, available online.

Fig. 1 shows that the great majority, 95%, of the sources are detected in the CO J = 4 → 3 line
and 86% of them have line strengths brighter than 5 K. Thus the CO J = 4 → 3 line is a readily-
detectable tracer of molecular material around ultracompact HII regions, and may be used as a
kinematic tracer and for distance determination. The profiles are in nearly all cases characterized
by a single component, whose Vlsr is in all but two cases the same as that of the CS J = 2 → 1 line,
within the fitting uncertainties. Those sources not detected at a level of several times the RMS
noise per channel are indicated in the table as upper limits, the level of which is estimated to be
4.5 times the RMS per channel.

Images of a selection of the brightest sources detected in the CO J = 4 → 3 line are shown in
Fig. 2. The images were formed by simply summing the emission in channels within the FWHM
of the Bronfman et al. (1996) Gaussian fit to the CS J = 2 → 1 line. The images have been
gridded onto a surface that over-samples the observed pointing centers by a factor of three using
a Gaussian smoothing function with FWHM 30% larger than the beam, and weighted using cone
interpolation with a similarly-sized interpolation radius. Bright molecular emission in the vicinity
of ultracompact HII regions often originates from hot cores, which are expected to be relatively
point-like compared with the AST/RO beam, except in those cases where an outflow is seen, where
more than one molecular core is present, or if the dense molecular region is genuinely extended.
Recent VLA results (Kurtz et al. 1999) show some ultracompact HII regions to lie within larger
structures that may also contain extended molecular material. From Fig. 2 it can be seen that at
least 50% of the sources in the present sample are unresolved by AST/RO and can potentially be
used by single dish telescopes for pointing purposes.

The point-like images shown in fig. 2 can be used to select sub-samples for pointing purposes
while extended structures may benefit from future mapping. These data will be combined with
and analyzed in the light of measurements made in several other lines with a variety of opacities
in a future paper.
 –5–

Table 1. Results of AST/RO observations

Name IRAS name R.A. (J2000) Dec. (J2000) TA

∗ (K) Vlsr I ∆V

G268.522 9028-4837 08:59:29.82 -48:13:17.31 2.8 ± 0.6a - - -

G269.854 9094-4803 09:11:08.40 -48:15:59.16 2.9 ± 0.5 78.8 ± 0.1 4.1 1.3
G281.586 10031-5632 10:04:56.23 -56:46:36.85 7.3 ± 0.1 -1.2 ± 0.1 45.2 5.8
G285.259 10295-5746 10:31:28.36 -58:02:07.47 23.3 ± 0.1 4.8 ± 0.0 129.9 5.2
G291.274 11097-6102 11:11:52.66 -61:18:35.38 25.3 ± 0.2 -20.9 ± 0.0 260.7 9.7
G297.725 11590-6452 12:03:22.80 -64:09:57.25 3.1 ± 0.8 -9.2 ± 0.1 2.3 0.7
G301.116 12331-6134 12:36:02.05 -61:51:05.41 9.6 ± 0.2 -39.0 ± 0.1 81.6 8.0
G301.134 12326-6245 12:35:33.87 -63:02:29.05 13.0 ± 0.2 -37.6 ± 0.1 87.0 6.3
G301.722 12:41:17.43 -61:44:10.45 10.9 ± 0.2 -38.6 ± 0.0 52.6 4.5
G301.731 12383-6128 12:41:17.42 -61:44:38.99 9.4 ± 0.3 -37.9 ± 0.1 53.9 5.4
G305.194 13:11:13.10 -62:44:56.10 11.7 ± 0.2 -33.9 ± 0.1 87.3 7.0
G307.559 13080-6229 13:32:30.47 -63:04:48.90 6.7 ± 0.2 -34.8 ± 0.1 28.2 3.9
G307.560 13291-6249 13:32:30.69 -63:05:17.36 7.3 ± 0.3 -33.4 ± 0.1 32.9 4.2
G309.920 13471-6120 13:50:41.53 -61:35:10.53 8.8 ± 0.3 -55.6 ± 0.1 31.2 3.3
G310.142 13484-6100 13:51:57.63 -61:15:45.78 7.9 ± 0.3 -54.9 ± 0.1 78.0 9.2
G312.599 14:13:13.88 -61:16:18.26 6.7 ± 0.2 -62.6 ± 0.1 47.0 6.6
G312.596 14095-6102 14:13:13.61 -61:16:47.12 6.2 ± 0.3 -60.8 ± 0.1 29.8 4.5
G318.047 14498-5856 14:53:41.34 -59:08:53.77 8.9 ± 0.2 -48.5 ± 0.1 65.7 7.0
G319.163 14593-5852 15:03:13.25 -59:03:53.96 6.9 ± 0.1 -20.4 ± 0.1 81.0 11.0
G320.674 15068-5733 15:10:43.24 -57:44:46.67 4.3 ± 0.3 -57.3 ± 0.1 19.4 4.3
G321.719 15100-5613 15:13:49.44 -56:24:55.02 7.9 ± 0.2 -39.6 ± 0.1 54.5 6.5
G322.933 15165-5524 15:20:21.12 -55:35:04.41 6.1 ± 0.6 -38.9 ± 0.1 6.6 1.0
G324.201 15290-5546 15:32:53.62 -55:56:12.40 8.9 ± 0.2 -85.7 ± 0.1 77.7 8.2
G326.466 15:43:17.74 -54:07:00.09 8.6 ± 0.1 -40.4 ± 0.1 108.6 11.8
G326.474 15394-5358 15:43:17.83 -54:07:32.62 7.5 ± 0.2 -38.9 ± 0.0 22.9 2.9
G326.655 15408-5356 15:44:42.79 -54:05:56.00 21.4 ± 0.2 -38.1 ± 0.0 224.8 9.9
G328.306 15:54:06.03 -53:11:07.59 2.0 ± 0.6 -8.9 ± 0.1 1.7 0.8
G328.307 15502-5302 15:54:06.01 -53:11:36.51 12.9 ± 0.2 -91.2 ± 0.1 116.2 8.5
G328.809 15520-5234 15:55:48.49 -52:42:40.20 3.4 ± 0.6 -101.3± 0.1 3.7 1.0
G329.337 15567-5236 16:00:32.89 -52:44:47.59 13.7 ± 0.0 -105.7 ± 0.0 94.8 6.5
G329.066 15573-5307 16:01:09.72 -53:16:01.76 4.9 ± 0.3 -47.3 ± 0.1 14.6 2.8
G329.404 15596-5301 16:03:31.25 -53:09:26.83 6.2 ± 0.3 -73.7 ± 0.1 36.0 5.5
G335.582 16272-4837 16:30:56.40 -48:43:46.39 3.7 ± 0.5 -66.4 ± 0.1 7.2 1.8
G330.883 16065-5158 16:10:21.83 -52:06:01.98 17.2 ± 0.2 -61.5 ± 0.0 132.0 7.2
G330.946 16060-5146 16:09:48.30 -51:54:52.36 8.7 ± 0.2 -88.3 ± 0.1 74.0 8.0
G331.126 16071-5142 16:10:56.83 -51:50:24.06 6.3 ± 0.2 -86.1 ± 0.1 42.5 6.4
G332.153 16:16:39.32 -51:16:28.40 10.6 ± 0.2 -54.9 ± 0.1 99.9 8.8
G332.293 16119-5048 16:15:45.15 -50:56:02.83 9.9 ± 0.3 -47.7 ± 0.0 31.5 3.0
G332.653 16158-5055 16:19:40.73 -51:03:10.97 11.3 ± 0.2 -47.4 ± 0.1 103.9 8.6
G332.831 16164-5046 16:20:14.28 -50:53:19.87 8.8 ± 0.2 -55.3 ± 0.1 117.7 12.6
G333.129 16172-5028 16:21:00.60 -50:35:19.84 22.4 ± 0.2 -50.5 ± 0.0 224.7 9.4
G333.306 16177-5018 16:21:30.61 -50:25:04.40 21.6 ± 0.2 -49.0 ± 0.0 225.1 9.8
 –6–

I thank K. Brooks and G. Garay for suggesting the sample; K. Xiao, C. Martin and A. Stark
for help with the observations; C. Walker and the receiver group at the U. of Arizona for their
assistance; R. Schieder, J. Stutzki, and colleagues at U. Köln for their AOSs; J. Kooi and R.
Chamberlin of Caltech, G. Wright of PacketStorm Communications, and K. Jacobs of U. Köln for
their work on the instrumentation. This research was supported in part by the National Science
Foundation under a cooperative agreement with the Center for Astrophysical Research in Antarctica
(CARA), grant number NSF OPP 89-20223. CARA is a National Science Foundation Science and
Technology Center. Support was also provided by NSF grant number OPP-0126090.

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 –7–

Table 1—Continued

Name IRAS name R.A. (J2000) Dec. (J2000) TA

∗ (K) Vlsr I ∆V

G337.164 16351-4722 16:36:20.15 -47:24:29.43 4.5 ± 0.2 -65.0 ± 0.2 55.1 11.6
G337.703 16348-4654 16:38:33.29 -47:01:20.00 4.9 ± 0.3 -52.7 ± 0.2 34.8 6.7
G338.569 16385-4619 16:42:14.29 -46:25:28.13 10.2 ± 0.3 -114.6 ± 0.1 54.0 5.0
G339.622 16424-4531 16:46:06.65 -45:36:49.42 5.7 ± 0.2 -32.6 ± 0.1 40.2 6.6
G340.053 16445-4516 16:48:11.89 -45:21:32.25 9.1 ± 0.2 -51.0 ± 0.1 77.2 8.0
G340.248 16458-4512 16:49:30.26 -45:17:49.66 8.3 ± 0.2 -49.5 ± 0.1 71.0 8.0
G341.932 16510-4347 16:54:37.12 -43:51:55.92 7.0 ± 0.3 -42.0 ± 0.1 33.4 4.5
G342.697 16:56:04.02 -43:04:13.54 6.1 ± 0.4 -40.9 ± 0.1 25.8 3.9
G342.704 16524-4300 16:56:01.29 -43:04:43.95 5.5 ± 0.9 -41.2 ± 0.1 4.3 0.7
G343.126 16547-4247 16:58:16.90 -42:51:37.00 8.4 ± 0.5 -28.4 ± 0.1 25.4 2.9
G345.001 17016-4124 17:05:09.79 -41:28:34.07 6.5 ± 0.8 -85.7 ± 0.1 9.5 1.4
G345.208 16571-4029 17:00:35.41 -40:33:31.17 23.2 ± 0.3 -13.9 ± 0.0 133.9 5.4
G345.482 17:04:26.83 -40:45:57.05 21.4 ± 0.4 -17.2 ± 0.1 155.5 6.8
G345.490 17009-4042 17:04:29.50 -40:46:25.47 13.2 ± 0.3 -16.3 ± 0.1 117.2 8.4
G345.494 16562-3959 16:59:41.88 -40:03:44.10 19.3 ± 0.2 -10.8 ± 0.1 192.6 9.4
G345.499 17008-4040 17:04:20.41 -40:44:25.77 13.1 ± 0.3 -16.4 ± 0.1 71.1 5.1
G345.505 17008-4040 17:04:23.06 -40:43:56.31 21.9 ± 0.4 -17.1 ± 0.1 172.8 7.4
G345.717 16596-4012 17:03:06.30 -40:17:08.73 7.1 ± 0.6 -9.0 ± 0.1 13.6 1.8
G348.236 17149-3916 17:18:23.91 -39:19:10.19 16.6 ± 0.3 -10.8 ± 0.1 109.7 6.2
G348.534 17158-3901 17:19:16.17 -39:04:26.09 10.3 ± 0.2 -11.2 ± 0.1 117.0 10.7
G348.548 17:19:16.05 -39:03:55.67 22.9 ± 0.5 -11.0 ± 0.1 208.2 8.5
G350.103 17160-3707 17:19:26.32 -37:10:54.75 9.1 ± 0.2 -68.0 ± 0.1 124.2 12.8
G350.504 17136-3617 17:17:02.20 -36:21:08.60 3.1 ± 0.6 15.7 ± 0.2 5.7 1.7
G351.776 17233-3606 17:26:44.44 -36:09:26.63 9.1 ± 0.2 -1.4 ± 0.1 112.9 11.6
G352.630 17278-3541 17:31:13.88 -35:44:09.07 4.9 ± 0.2 -0.4 ± 0.2 62.9 11.9
G353.410 17:30:26.47 -34:41:09.16 26.5 ± 0.6 -15.0 ± 0.1 313.6 11.1
G353.416 17271-3439 17:30:28.87 -34:41:40.53 11.8 ± 0.3 -14.6 ± 0.1 153.8 12.3
G357.552 17385-3116 17:41:49.73 -31:18:22.66 14.1 ± 0.4 3.4 ± 0.1 54.0 3.6
G000.665 17441-2822 17:47:19.66 -28:23:08.21 4.5 ± 1.0a - -
G005.633 17545-2357 17:57:33.60 -23:58:15.12 4.8 ± 0.9a - - -
G005.888 17574-2403 18:00:32.09 -24:04:02.75 18.5 ± 0.4 10.0 ± 0.1 123.9 6.3
G008.139 17599-2148 18:03:00.39 -21:48:04.92 7.8 ± 0.4 21.3 ± 0.2 44.6 5.4
G009.615 18032-2032 18:06:13.42 -20:31:47.22 9.3 ± 0.4 7.0 ± 0.1 58.8 6.0
G010.157 18064-2020 18:09:24.44 -20:19:27.99 7.4 ± 0.3 9.8 ± 0.3 107.6 13.7
G010.466 18056-1952 18:08:36.63 -19:52:03.35 6.9 ± 0.4 72.3 ± 0.3 62.6 8.5
G011.936 18110-1854 18:14:00.34 -18:53:22.22 5.0 ± 1.8a - - -

a
Upper limit: see text.
 –8–

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This preprint was prepared with the AAS LATEX macros v5.0.
–9–
 – 10 –

G005.888 G281.566 G285.259 G291.274

25 10 25 30

20 8 25
20
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

15 6 20
15

10 4 15

10

5 2 10

5
0 0 5

0
-5 -2 0

-10 -4 -5 -5
-20 -10 0 10 20 30 40 -30 -20 -10 0 10 20 30 -20 -10 0 10 20 30 -50 -40 -30 -20 -10 0 10
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G301.116 G301.134 G301.722 G301.731

12 15.0 12 12

10 12.5 10 10
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

8 10.0 8 8

6 7.5 6 6

4 5.0 4 4

2 2.5 2 2

0 0.0 0 0

-2 -2.5 -2 -2

-4 -5.0 -4 -4
-70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G305.194 GG307.559 G309.920 G310.142

20 8 10 12.5

10.0
8
6
15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

7.5
6
4
5.0
10
4

2 2.5

2
5
0.0
0
0
-2.5
0
-2
-2
-5.0

-5 -4 -4 -7.5
-90 -80 -70 -60 -50 -40 -30 -20 -10 -60 -50 -40 -30 -20 -10 -90 -80 -70 -60 -50 -40 -30 -80 -70 -60 -50 -40 -30
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G312.596 G312.599 G318.047 G319.163

10 10 15.0 8

12.5
8 8
6
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

10.0
6 6
4
7.5
4 4

5.0 2

2 2
2.5
0
0 0
0.0

-2
-2 -2
-2.5

-4 -4 -5.0 -4
-90 -80 -70 -60 -50 -40 -30 -90 -80 -70 -60 -50 -40 -30 -80 -70 -60 -50 -40 -30 -20 -60 -50 -40 -30 -20 -10 0 10
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G320.674 G321.719 G324.201 G326.466

8 12 12 12

6 10 10 10
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

4 8 8 8

2 6 6 6

0 4 4 4

-2 2 2 2

-4 0 0 0

-6 -2 -2 -2

-8 -4 -4 -4
-90 -80 -70 -60 -50 -40 -30 -70 -60 -50 -40 -30 -20 -10 -120 -110 -100 -90 -80 -70 -60 -80 -60 -40 -20 0
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G326.655 G328.307 G329.066 G329.337

25 20 8 15.0

12.5
6
20
15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

10.0
4
15
7.5
10
2

10 5.0

0
5
2.5
5
-2
0.0
0
0
-4
-2.5

-5 -5 -6 -5.0
-70 -60 -50 -40 -30 -20 -10 -120 -110 -100 -90 -80 -70 -60 -70 -60 -50 -40 -30 -20 -10 -140 -130 -120 -110 -100 -90 -80
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

Fig. 1.— Spectra toward the sources listed in Table 1.

 – 11 –

G329.404 G330.883 G330.946 G331.126

12 20 12 10

10 10
8
15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

8 8
6

6 6
10
4

4 4

2
5
2 2

0
0 0
0
-2
-2 -2

-4 -5 -4 -4
-100 -90 -80 -70 -60 -50 -90 -80 -70 -60 -50 -40 -30 -120 -110 -100 -90 -80 -70 -60 -120 -110 -100 -90 -80 -70 -60
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G332.536 G332.293 G332.653 G332.831

15.0 12 15.0 12

12.5 10 12.5 10
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

10.0 8 10.0 8

7.5 6 7.5 6

5.0 4 5.0 4

2.5 2 2.5 2

0.0 0 0.0 0

-2.5 -2 -2.5 -2

-5.0 -4 -5.0 -4
-90 -80 -70 -60 -50 -40 -30 -20 -80 -70 -60 -50 -40 -30 -20 -80 -70 -60 -50 -40 -30 -20 -90 -80 -70 -60 -50 -40 -30
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G333.129 G333.306 G337.164 G337.703

30 30 10.0 10

25 25 7.5 8
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

6
20 20 5.0

4
15 15 2.5

10 10 0.0
0

5 5 -2.5
-2

0 0 -5.0
-4

-5 -5 -7.5 -6
-80 -70 -60 -50 -40 -30 -20 -80 -70 -60 -50 -40 -30 -20 -90 -80 -70 -60 -50 -40 -80 -70 -60 -50 -40 -30 -20
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G338.569 G340.053 G340.248 G341.932

15.0 12 12.5 10

12.5 10 8
10.0
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

10.0 8 6
7.5

7.5 6 4
5.0

5.0 4 2

2.5
2.5 2 0

0.0
0.0 0 -2

-2.5
-2.5 -2 -4

-5.0 -4 -5.0 -6
-150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -80 -70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G342.697 G342.704 G343.126 G345.001

12.5 10.0 10 8

10.0
7.5 8 6
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

7.5
5.0 6 4

5.0
2.5 4 2

2.5

0.0 2 0
0.0

-2.5 0 -2
-2.5

-5.0 -2 -4
-5.0

-7.5 -7.5 -4 -6
-70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10 -60 -50 -40 -30 -20 -10 0 -120 -110 -100 -90 -80 -70 -60 -50
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G345.208 G345.482 G345.490 G345.494

30 25 20 25

25
20
20
15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

20
15
15
15
10
10

10 10

5
5
5
5
0
0
0
0
-5
-5

-10 -10 -5 -5
-40 -30 -20 -10 0 10 -40 -30 -20 -10 0 10 20 -50 -40 -30 -20 -10 0 10 -40 -30 -20 -10 0 10 20
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

Fig. 1.— Continued

 – 12 –

G345.499 G345.505 G345.717 G348.236

20 30 12.5 20

25 10.0

15 15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

20 7.5

15 5.0
10 10

10 2.5

5 5
5 0.0

0 -2.5
0 0

-5 -5.0

-5 -10 -7.5 -5
-40 -30 -20 -10 0 10 -60 -40 -20 0 20 -40 -30 -20 -10 0 10 20 -40 -30 -20 -10 0 10
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G348.534 G348.548 G350.103 G351.776

15.0 30 15.0
12

12.5 12.5
10
20
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

10.0 10.0 8

7.5 7.5 6
10

5.0 5.0 4

0
2.5 2.5 2

0.0 0.0 0
-10

-2.5 -2.5 -2

-5.0 -20 -5.0 -4

-40 -30 -20 -10 0 10 20 -40 -30 -20 -10 0 10 20 30 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G352.630 G353.410 G353.416 G357.552

12.5 50 25 20

10.0 40 20
15
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

7.5 30 15

10
5.0 20 10

2.5 10 5
5

0.0 0 0

0
-2.5 -10 -5

-5.0 -20 -10 -5

-30 -20 -10 0 10 20 30 -60 -40 -20 0 20 -50 -40 -30 -20 -10 0 10 -30 -20 -10 0 10 20 30
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G350.504 G339.622 G335.582 G332.153

15 8
10 15.0

6
8 12.5
10
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

6 4 10.0

4 2 7.5
5

2 0 5.0

0
0 -2 2.5

-2 -4 0.0
-5
-4 -6 -2.5

-10 -6 -8 -5.0
-40 -30 -20 -10 0 10 20 -60 -50 -40 -30 -20 -10 0 -80 -70 -60 -50 -40 -30 -90 -80 -70 -60 -50 -40 -30 -20
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G328.306 G326.474 G322.933 G307.560

8 10 10 10

8
8 8
6
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

6
6 6
4
4
4 4

2 2

2 2
0
0
0 0
-2

-2
-2 -2
-4

-4 -4 -6 -4
-100 -80 -60 -40 -20 0 -70 -60 -50 -40 -30 -20 -10 -70 -60 -50 -40 -30 -20 -10 -60 -50 -40 -30 -20 -10 0
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G297.725 G281.586 G269.854 G268.522

6 10 8
8

8 6 6
4
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

4
6 4
2
2
4 2

0 0

2 0
-2
-2
0 -2
-4

-4
-2 -4 -6

-8
-6 -4 -6 -20 -10 0 10 20 30
-30 -20 -10 0 10 20 -30 -20 -10 0 10 20 30 50 60 70 80 90 100
Velocity (km/s)
Velocity (km/s) Velocity (km/s) Velocity (km/s)

Fig. 1.— Continued

 – 13 –

G000.665 G005.633 G008.139 G009.615

10.0 15 15 20

7.5
10 15
10
Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

Antenna Temperature (K)

5.0

5 10
2.5
5

0.0 0 5

0
-2.5
-5 0

-5.0
-5
-10 -5
-7.5

-10.0 -15 -10 -10

-10 0 10 20 30 40 50 20 40 60 80 100 120 -10 0 10 20 30 40 50 -20 -10 0 10 20 30
Velocity (km/s) Velocity (km/s) Velocity (km/s) Velocity (km/s)

G010.157 G010.466
20 20

15
15
Antenna Temperature (K)

Antenna Temperature (K)

10
10

0
-5

-5
-10

-10 -15
-20 -10 0 10 20 30 40 50 40 50 60 70 80 90 100
Velocity (km/s) Velocity (km/s)

Fig. 1.— Continued

 – 14 –

Fig. 2.— Images of the brightest hot cores in the CO J = 4 → 3 line. The figures show the emission
in the CO(4-3) line as both a greyscale and contours (5% to 95% of peak in 10% steps).
 – 15 –

Fig. 2.— Continued

 – 16 –

G345.499 G345.505 G345.717 G348.236

G348.534 G348.548 G350.103 G351.776

G352.630 G353.410 G353.416 G357.552

Fig. 2.— Continued