The Giant Herbig-Haro Flow HH 212 and Associated Star Formation
  The bipolar jet HH 212, among the finest collimated jets known, has so far
been detected only in near-infrared H$_2$ emission. Here we present deep
optical images that show two of the major bow shocks weakly detected in optical
[SII] emission, as expected for a bona fide Herbig-Haro jet. We present
widefield H$_2$ images which reveal two more bow shocks located symmetrically
around the source and along the main jet axis. Additionally, examination of
Spitzer 4.5 $\mu$m images reveals yet another bright bow shock further to the
north along the jet axis; no corresponding bow shock is seen to the south. In
total, the HH 212 flow has an extent of 1050 arcsec, corresponding to a
projected dimension of 2.0 pc. HH 212 thus joins the growing group of
parsec-scale Herbig-Haro jets. Proper motion measurements indicate a velocity
of about 170 km/sec, highly symmetric around the source, with an uncertainty of
$\sim$30 km/sec, suggesting a probable age of the giant HH 212 flow of about
7000 yr. The jet is driven by a deeply embedded source, known as IRAS
05413-0104. We draw attention to a Spitzer near- and mid-infrared source, which
we call IRS-B, located only 7 arcsec from the driving source, towards the
outskirts of the dense cloud core. Infrared photometry and spectroscopy
suggests that IRS-B is a K-type star with a substantial infrared excess, except
that for an extinction of A$_V$ = 44 the star would have only a weakinfrared
excess, and so in principle it could be a K-giant at a distance of about 2 kpc.
