IPHAS Spectroscopic followup

1
IPHAS 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
2
The 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

3
Target 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

4
Pipeline extraction of fibers
TDC pipeline at CfA produces 300 extracted fiber
spectra
Ha
skylines
5
5 sky offset exposure (extracted)
Target exposures followed by offset sky exposure
variable background emission
relatively stable sky background pattern
6
Science spectra 1D reduction
extracted target fiber including background
7
Custom 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
8
Optimal 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
9
Background subtraction target
10
Flux 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
11
Flux corrections mean response for a config
12
(Relative) flux corrected spectrum
13
A typical batch in Cyg-X field 7
14
A typical batch in Cyg-X field 7
15
The 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

16
The HectoSpec Harvest

• Library of spectra allows for powerful feedback
  between follow-up and target selection/identificat
  ion using the IPHAS photometry

17
Higher 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

18
MOS 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