SALT s Venture into Near Infrared Astronomy with RSS NIR Marsha Wolf University of Wisconsin Madison IUCAA
RSS VIS future RSS NIR 5 June 2015 SALT Science Conference 2015 2
Robert Stobie Spectrograph 5 June 2015 SALT Science Conference 2015 3
RSS NIR Capabilities As delivered: Simultaneous VIS NIR Dichroic split at =0.9 um Imaging (no BB filters) Longslit or multi object spectroscopy R ~ 3000 7000 Sky limited to ~1.55 um Photon limited to = 1.7 um Potential upgrades: Add broadband filters Add gratings, R ~ 1000 7000 Cool slit to reach ~ 1.67 um Upgrade path to polarimetry Upgrade path to Fabry Perot Predicted performance R ~ 7000 1 hour exposure S/N ~ 10 J & H ~ 20 5 June 2015 SALT Science Conference 2015 4
RSS NIR Spectral Coverage Suite of 6 VPH gratings designed Only 1 grating delivered initially 950 l/mm to best cover the entire spectral range 3000 < R < 7000 (1 slit) 5 June 2015 SALT Science Conference 2015 5
Time Resolved Spectroscopy HAWAII 2RG detector (2048 x 2048 pixels) Optimized for operation at 200 khz Total chip readout time: 1.4 sec 0.7 sec read time 0.7 sec reset of chip at beginning of exposure Windowing mode available Read time reduces by ~ number of pixels 5 June 2015 SALT Science Conference 2015 6
RSS NIR Project Status 5 June 2015 SALT Science Conference 2015 7
Camera Testing 5 June 2015 SALT Science Conference 2015 8
Detector/Dewar Systems 5 June 2015 SALT Science Conference 2015 9
RSS NIR Schedule Ready to ship: April 2016 Driven by custom insulated enclosure (pre dewar) & cooling system Installation & Commissioning: Feb 2017 But, that s not the end of the story 5 June 2015 SALT Science Conference 2015 10
An Interim Configuration Strong motivation to maximize SALT science productivity and minimize telescope downtime Mount RSS NIR in the spectrometer room next to HRS Feed it with a fiber integral field unit (IFU) Keep the option open for mounting on Tracker and mating it to RSS VIS in the future 5 June 2015 SALT Science Conference 2015 11
RSS NIR Capability Comparison Mated to RSS VIS on Tracker Simultaneous VIS NIR Dichroic split at = 0.9 um Imaging (no BB filters) Longslit or multi object spectroscopy Sky limited to ~1.55 um Photon limited to = 1.7 um Fiber Fed in Spectrograph Room Only NIR NO imaging Integral field spectroscopy 0.8 1.7 um Sky limited to ~ 1.7 um Potential Upgrades: Add broadband filters Cool slit to reach ~ 1.65 um Upgrade path to polarimetry Upgrade path to Fabry Perot Potential Upgrades: Fiber positioner for MOS NO upgrade to polarimetry NO upgrade to Fabry Perot 5 June 2015 SALT Science Conference 2015 12
Conceptual IFUs IFU concept #1 457 science fibers 28 sky fibers separated by 1.5 arcmin 0.6 diameter 0.7 pitch Overall size 11 x 17 R ~ 10,000 IFU concept #2 305 fibers, 28 sky fibers 0.9 diameter 1.1 pitch Overall size 17 x 21 R ~ 5000 IFU #1 Maximize spectral resolution with 0.6 pseudo slit IFU #2 Closer matched to seeing Larger field coverage 5 June 2015 SALT Science Conference 2015 13
Well Suited to Nearby Galaxies Examples from SDSS IV MaNGA survey 61 fiber MaNGA IFU (2 fibers) has 22.5 diameter Overlays of 17 x 21 RSS NIR IFU, containing 305 1 fibers J1057+3616 z = 0.030 R e = 3.4 J1352+1359 z = 0.024 R e = 7.3 J0937+2140 z = 0.019 R e = 9.3 5 June 2015 SALT Science Conference 2015 14
RSS NIR Schedule Previous schedule Ready to ship: April 2016 Installation & Commissioning complete: Feb 2017 Fiber fed option Driven by new collimator design, construction, testing Ready to ship: Feb 2017 Installation & Commissioning complete: July 2017 5 June 2015 SALT Science Conference 2015 15
NIR Science Constraining stellar populations 5 June 2015 SALT Science Conference 2015 16
NIR Stellar Spectra What about that extra region from 1.55 to 1.7 um? Dwarf sequence Giant sequence Rayner et al. 2009 5 June 2015 SALT Science Conference 2015 17
NIR IFU Science: Ancillary Data for Optical IFU Galaxy Surveys CIRPASS IFU spectra on Gemini 1.45 1.67 um Extra constraints on galaxy star formation (SF) histories, especially recent SF [Fe II]1.644um (z~0.03 w/1.7um cutoff) Strong emission in partially ionized zones or shock excited gas from SNe Diffuse, spatially extended associated with galactic winds Lower limit on time since SF was induced, ~35 55 Myr H Br (1.641, 1.611, 1.588 um) Recombination of ionized gas in H II regions created by young, massive stars NGC 1140 older younger Fades after ~8 Myr de Grijs et al. 2004 5 June 2015 SALT Science Conference 2015 18
younger starburst older starburst CO bandhead absorption also indicates young stars, ~7 10 Myr 5 June 2015 SALT Science Conference 2015 19
Extraplanar Ionized Gas is Fairly Common in MaNGA Diamond Stanic, Tremonti 5 June 2015 SALT Science Conference 2015 20
NIR Science: Constraining the Stellar IMF IMF used in stellar pop models can change M/L by 3 4x Gravity sensitive NIR lines Wing Ford band, FeH @ 9915 Å Na I doublet 8190 Å Ca I @ 10,345 Å IMF correlates with /Fe Rapid starbursts formed larger number low mass stars per solar mass /Fe not in most stellar pop models Ca I 10,345 line insensitive to Na abundance (which depends on /Fe) Smith et al. 2012 5 June 2015 SALT Science Conference 2015 21
Summary The NIR spectrum is rich with less dust extincted spectral features to: Better constrain young stellar populations Constrain the low mass end of the stellar IMF Detect shocks from supernovae and stellar winds Spatially resolved IFU spectra will provide important ancillary data on galaxy feedback SALT can play an exciting role in more detailed followup of objects identified in large optical IFU surveys An integral field RSS NIR will be here in 2017 5 June 2015 SALT Science Conference 2015 22
Thank you
Observations of SNe IIn SN 2010jl Borish et al. 2015 Br & Pa broad lines Optical lines optically thick, NIR are not Emission line profiles consistent with electron scattering in circumstellar medium He I 10830 Difference with H lines Blue shoulder implies H poor ejecta expanding into low circumstellar density NIR continuum Info on warm dust emission at later times, after photoshperic emission has faded NIR Science: Time Evolution of Supernovae 5 June 2015 SALT Science Conference 2015 24
NIR Science: Accretion Driven Stellar Wind He I 10830 Shows less night to night absorption variability than H, suggesting large scale wind outflow from star Emission correlates with velocity of accreting inflowing material Stellar wind velocity related to strength of He emission Accretion process leads to wind acceleration Dupree et al. 2014 5 June 2015 SALT Science Conference 2015 25
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28 May 2015 SALT Board Meeting 37 Cape Town 27