Figure 4.
Continuum-subtracted
TEXES spectrum (black)
and dominant “hot”
model fit (blue), which
yields the temperature
(450 K) and location
(0.3 AU) of the
emitting water vapor.
A “warm” component
(red) is required to
account for additional
measurements at
longer wavelengths.
The sum of the models
is plotted in gray.
called “transition disks” in showing evidence
for water; yet by later stages of evolution, as
young stars with disks, water vapor emission
is common. The inner ring of DoAr 44 may
be replenished by material from the outer
disk, accounting for the large water content
it maintains compared with similar objects.
Alternatively, planets may affect the chemistry in this region where terrestrial planets
develop.
The warm (450 K) water arises in the inner
ring, appearing in emission at mid-infrared
wavelengths (Figure 4). The data were obtained at a spectral resolution R ~ 80,000
using the Texas Echelon Cross Echelle Spectrograph (TEXES), a visitor instrument on the
10
GeminiFocus
Gemini North telescope. Colette Salyk (National Optical Astronomy Observatory and
Vassar College) and collaborators used the
kinematic characteristics of the spectrally
resolved emission to determine the location
of its origin, at 0.3 AU. Avoiding destruction
of water molecules in this region close to the
stellar source requires material in the region
— either gas or dust — as protection against
the star’s strong radiation. The paper will appear in The Astrophysical Journal Letters and a
preprint is now available.
Nancy A. Levenson is Deputy Director and Head
of Science at Gemini Observatory and can be
reached at: [email protected]
October 2015