1) Slit width and slit PA
slit width slit PA
GCS3-2 0".2/0".4 any
GC IRS3/1 0".4 PA=113.5 (from the north to the east)
[NHS93] 21 0".4 any
ISOGAL-J17 0".4 any
Slit PA:
We request the slit PA=113.5 (from the north to the east) for GC
IRS1/3 in order to cover both of the objects in the same time,
which are only 6" apart. For all the others, the targets are point
sources, or nearly point sources, we do not care about the position
angle of the slit. Any position angle will do. Finding charts are
attached.
Slit width:
We have a fairly good s/n data for GCS 3-2 with R=60,000 from
Phoenix at the Gemini South. Then, we might request, if the
circumstances allow, the highest spectral resolution with 0".2 slit
for GCS 3-2, because it makes the least risk of the slit loss,
since GCS 3-2 is the brightest one (L=3.03). Although GCS 3-2 is
the best target to verify the highest spectral resolution mode of
the instrument in this season, in the case that the instrument
status does not allow, the spectrum with R=50,000 with 0.4 slit
will do also. For others, the good s/n data have been never
obtained with spectral resolution as high as R=50,000. Therefore we
request the standard 0".4 slit for the better s/n.
2) Priority and the minimum set of data to be meaningful:
a) GCS 3-2 is the first priority, and makes a minmum dataset for the
science goal
b) GC IRS3/IRS1 is the next
c) then [NHS 93] 21 and ISOGAL-J17
3) AO: the wavefront references sources for AO are following.
ID(USNO-B1.0) R [mag] dist[arcsec] PA(obj->ref)
GCS3-2 0611-0602187 15.04 8" 97
GC IRS3/1 0609-0602733 13.5 17" 37
[NHS93] 21 0611-0602026 14.5 16" 164
ISOGAL-J17 0609-0603617 13.5 25" 176
The spatial resolution is NOT the issue for our primary science
goal. We are only interested in the use of AO in terms of the
increased slit throughput, and in the case that AO makes the
observing efficiency better.
We understand, our AO guide stars are not the optimum cases,
typically R=14 mag stars at 10"-25" away from the targets. In the
case that it takes time to lock the telescope on the AO guide star,
and would result more observing time in total than the case
observing without AO, we are happy to do without AO. In any case,
according to the ETC calculation, all the objects reach sufficient
s/n with or without AO.
4) ABBA nodding: We assume the data will be obtained by nodding the
telescope by 25" (arbitrary taken as half of the slit
length. Please change it, if other numbers are favorable, for
example in terms of avoiding bad pixels and cracks on the
detectors) along the slit in regular a-b-b-a sequence.
5) Calibration: we need spectroscopic flat fields, for each grating
settings. At all the wavelength regions we target (3715nm, 3534nm,
2338-2346nm, 4730-4809nm), we have plenty of sky emission lines
useful for the absolute wavelength calibration. Thus, separate arc
lamp exposure is not necessary.
6) 'Telluric' standard stars are necessary in order to remove the
atmospheric absorption lines and should be observed through similar
airmass to the program stars with differences within 0.1.
'Spectroscopic' or flux calibration stars are not necessary, since
our primary interest is to measure the equivalent widths of the
absorption lines, which is done with respect to the continuum flux
of the object stars.
7) The line list:
We request two H3+ lines for each objects, and several CO lines at
the 2.3 um overtone band, except GC IRS3 and IRS1 whose K magnitude
is somewhat faint. Instead, we request the fundamental transitions
of 13CO and C18O at 4.73-4.81 um, which are covered simultaneously.
Margins of +-250km/s (3nm) at both sides of the lines are
desirable.
wavelength [nm]
H3+ R(1,1)l 3715.47
H3+ R(3,3)l 3533.66
CO v=2-0 R(0) 2345.31
R(1) 2343.27
R(2) 2341.28
R(3) 2339.32
R(4) 2337.41
R(5) 2335.54
13CO v=1-0 P(4) 4804.99
P(3) 4796.30
P(2) 4787.71
P(1) 4779.22
R(0) 4762.56
R(1) 4754.39
R(2) 4746.31
R(3) 4738.34
R(4) 4730.47
C18O v=1-0 P(3) 4805.29
P(2) 4796.70
P(1) 4788.21
R(0) 4771.55
R(1) 4763.38
R(2) 4755.31
R(3) 4747.34
R(4) 4739.47
8) Exposure time consideration.
[nm] slit w/AO(pix count/sn) w/o AO(pix count/sn)
GCS3-2 3715 0.2 12s,4(40243e/510) 12s,4(11342e/520)
0.4 12s,4(47593e/548) 12s,4(14678e/576)
GC_IRS3 3715 0.2 120s,4(55427e/531) 120s,4(17406e/475)
0.4 100s,4(56406e/496) 120s,4(24928s/497)
GC_IRS1 3715 0.2 120s,4(50890e/503) 120s,4(16215e/445)
0.4 100s,4(52011e/468) 120s,4(23415e/454)
[NHS93]_21 3715 0.2 60s,4(45958e/522) 60s,4(14598e/505)
0.4 60s,4(56182e/552) 60s,4(19945e/534)
ISOGAL-J17 3715 0.2 120s,4(59841e/576) 120s,4(20146e/538)
0.4 90s,4(55952e/521) 120s,4(28403e/557)