Star Forming Regions in Cepheus

44
molecular core associated with FIRS 2, and Fuente et al. (2005b) carried out a molecular
survey of FIRS 2 and LkHα 234 with the aim of studying the chemical evolution of
the envelopes of intermediate-mass young stellar objects. Fuente (2008) present high
angular resolution imaging of the hot core of NGC 7129 FIRS 2, using the Plateau de
Bure Interferometer. This is the first chemical study of an intermediate-mass hot core
and provides important hints to understand the dependence of the hot core chemistry
on the stellar luminosity.
Two molecular outflows were found in NGC 7129 by Edwards & Snell (1983).
They seem to be associated with LkHα 234 and FIRS 2. Weintraub et al. (1994), via
near infrared polarimetry, identified a deeply embedded source, NGC 7129 PS 1, located
about 3 ′′ northwest of LkHα 234. This source was not identified in the direct
near-infrared images of LkHα 234, which revealed 5 sources (IRS 1–IRS 5, IRS 1 ≡
LkHα 234) in a 20 ′′ × 20 ′′ field centered on LkHα 234. Weintraub et al. (1996) detected
NGC 7129 PS 1 at 3.8 µm, and proposed that it was the actual outflow source
instead of LkHα 234.
Cabrit et al. (1997) present high-resolution imaging of the region around LkHα 234
in the 10 µm and 17 µm atmospheric windows and in the H 2 v=1-0 S(1) line and adjacent
continuum. The cold mid-infrared companion, detected at 2.7 ′′ to the north-west
of the optical star, corresponds to NGC 7129 PS 1. The companion illuminates an arcshaped
reflection nebula with very red colors, and is associated with a radio continuum
source, H 2 O masers, and a bright extended H 2 emission knot, indicating that it is deeply
embedded and has strong outflow activity. Cabrit et al. (1997) refer to this star as IRS 6,
extending Weintraub et al.’s notation.
Fuente et al. (2001) obtained single-dish and interferometric continuum images at
2.6 mm and 1.3 mm of both FIRS 2 and LkHα 234. They identified two millimeter
sources associated with FIRS 2: FIRS 2–MM1, apparently associated with the CO outflow,
and a weaker source, FIRS 2–MM2, which does not present any sign of stellar activity.
The interferometric 1.3 mm continuum image of FIRS 1 reveals that LkHα234 is
a member of a cluster of embedded objects. Two millimeter clumps are associated with
this far-infrared source. The stronger is spatially coincident with IRS 6. A new millimeter
clump, FIRS 1–MM1, is detected at an offset (−3.23 ′′ , 3.0 ′′ ) from LkHα 234. The
extremely young object FIRS 1–MM1 (it has not been detected in the near- and midinfrared)
is the likely driving source of the H 2 jet. There is no evidence for the existence
of a bipolar outflow associated with LkHα 234. In addition to FIRS 1 and FIRS 2, six
other compact millimeter clumps are detected in the region, NGC 7129 MM1 to MM5
(see Fig. 13), and the sixth coincides with the bipolar nebula RNO 138.
Submillimeter continuum observations by Font et al. (2001) revealed three compact
sources: LkHα 234 SMM 1, LkHα 234 SMM 2 and FIRS 2. SMM 1 coincides
with IRS 6, which, according to the submillimeter observations, may be a deeply embedded
Herbig Be star, whereas SMM 2 is a newly discovered source (see Figure 14).
Table 8 shows the coordinates, wavelengths of detection, measured fluxes and sizes of
the deeply embedded young stellar objects in NGC 7129, observed in submillimeter,
millimeter, and centimeter continuum.
Low-mass pre-main sequence members of NGC 7129 were identified as Hα emission
objects by Hartigan & Lada (1985), Miranda et al. (1993), and Magakian et al. (2004),
as variable stars (Semkov 2003) and near-infrared sources (Strom et al. 1976; Cohen
& Schwartz 1983). Muzerolle et al. (2004) presented observations of NGC 7129 taken
with the Multiband Imaging Photometer for Spitzer (MIPS). A significant population