Title: IPHAS Spectroscopic followup
1IPHAS Spectroscopic follow-up With the
MMT/HectoSpec Danny Steeghs Harvard-Smithson
ian Center for astrophysics Janet Drew, Robert
Greimel, Yvonne Unruh, Boris Gaensicke SAO Dan
Fabricant, Nelson Caldwell, Susan Torquaz, Perry
Berlind
2The MMT HectoSpec combination
- The MMT is now a monolithic 6.5m telescope, with
a f/5 secondary delivering a 1 field of view - HectoSpec is a bench mounted fiber-fed MOS with a
array of 300 fibers and two fiber positioners to
cover the full FOV - The robots Fred Ginger setup a fiber
configuration within 5 minutes - 300/600 gratings available, provide 2-6Å
resolution with the 1.5 fibers - IPHAS follow-up is a long-term program since
commissioning in 2004
3Target selection and strategy
- Targets are selected from the IPHAS r-i, r-H?
CMDs - Targets are assigned weights depending on their
colors and how many selection criteria are met - In order to achieve good target completion , two
configs with 260 targets are optimised from a
target selection of 600 - Configs consist of a set of 3-4 identical
exposures followed by a small telescope slew to
obtain an offset sky exposure
4Pipeline extraction of fibers
TDC pipeline at CfA produces 300 extracted fiber
spectra
Ha
skylines
55 sky offset exposure (extracted)
Target exposures followed by offset sky exposure
variable background emission
relatively stable sky background pattern
6Science spectra 1D reduction
extracted target fiber including background
7Custom background subtraction
fiber sky
30-40 fibers per config provide sparse but
simultaneous sky coverage over the field of view
offset sky
offset exposure provides a nearby sky for each
fiber
8Optimal sky subtraction
Optimal (variance weighted) sky template is
generated by minimising the residuals near strong
sky lines
targetsky
sky template
Provides scaling factor for optimal subtraction
, independently evaluated for both sky fiber and
offset sky
9Background subtraction target
10Flux corrections Boris Gänsicke
Exploit the generous presence of M-stars in our
configs to determine flux calibration through
template matching
Best matching spectral template provides a flux
correction
11Flux corrections mean response for a config
12(Relative) flux corrected spectrum
13A typical batch in Cyg-X field 7
14A typical batch in Cyg-X field 7
15The HectoSpec Harvest
- 44 configs covering 22 sqr.degs on the sky have
been observed, producing 12,400 spectra - Harvest includes a wide variety of objects, with
a good hit rate on emission line objects, and a
good selection of interesting objects in each
config - Examples include lots of late type emission line
objects, white dwarfs, interacting binaries, T
Tauris / PMS, symbiotics, nebular objects and
even AGN
16The HectoSpec Harvest
- Library of spectra allows for powerful feedback
between follow-up and target selection/identificat
ion using the IPHAS photometry
17Higher resolution kinematics
- First tests with a 600gpmm grating covering the
Ca NIR triplet is promising in terms of allowing
kinematics/ abundance studies using early-type
objects - Needs fine-tuned target selection but instrument
stability good - Complements the low-resolution identification
spectra obtained with the 270gpmm setup
18MOS followup and IPHAS/EGAPS
- MOS follow-up is essential in order to evaluate
relevant target selection criteria from imaging
CMDs - Versatility permits all-at-once approach of a
wide - range of science programs
- H? diagnostic is effective good efficiency in
picking - up true emission line objects
- Large database of spectra allows feedback and
tests of reddening modeling etc. for individual
fields as well as a census of its strong emitters
(but is a lot of work!) - Several spin-off projects in progress
- gt12,000 spectra currently hosted at CfA, plan for
a more friendly interface with other IPHAS info
- http//hea-www.cfa.harvard.edu/dsteeghs
- IPHAS as follow-up testing ground for future
EGAPS projects