The Habitable Zone Planet Finder

A high-resolution NIR spectrograph for the Hobby Eberly Telescope

Suvrath Mahadevan

Pennsylvania State University

Larry Ramsey, Alex Wolszczan, Jason Wright (PSU), Michael Endl (UT), Bo Zhao (UF) , Stephen Redman (PSU)

On behalf of the HZPF Team

Earths & Super Earths around M stars

1 m/s

0.1 m/s

Kasting et al. 1993

M dwarfs lower mass and lower luminosity. HZ is closer, Doppler amplitude of a terrestrial planet is upto 10x higher that that around a G2V star HZ.

Earths & Super Earths around M stars

Recommendations to develop NIR Precision RV techniques from ExoPTF and Blue Dots

ExoPTF Lunine et al. 2008

Earths & Super Earths around M stars

Jones et al. 2009

Mid/Late M stars are attractive targets since RV amplitude of terrestrial planets is so much higher than around F, G, K. Much beyond M4 are as yet unprobed by precision RVs.

NIR follow-up observations can be very helpful when claiming detection of planets around young/active stars (Prato et al. 2008)

Setiawan et al. 2008

Claimed detection of planet around the young active star TW Hya shown to be due to activity induced RV effects – Huelamo et al. 2008

Precision RVs in the NIR

NIR follow-up observations very important to confirm ground based astrometric candidates around low mass planets

Zapatero Osorio et al. 2009

Precision RVs in the NIR

Vb10 Pravdo & Shaklan 2009

V= 17.3 , H=9.22

Pathfinder : One that discovers a new course or way, especially through or into unexplored regions.

• Penn State NIR Pathfinder spectrograph is a lab test bed to explore challenges in precision NIR radial velocities.

• Initial Motivation was to retire some of the risk in the Gemini PRVS proposal, which it succeeded in doing.

• Now going beyond to explore more of the fundamental issues in NIR velocity extraction.

• Pathfinder is a lab prototype build as a testbed from existing and available parts. Uncooled, not highly temperature stabilized, uses a H1 array that is sensitive to 2.7um, so background is high.

• Still a VERY useful way to test RV precision, extraction, calibration techniques etc in what is still a somewhat unexplored domain at ~3-5m/s precision. Will focus on the fiber fed simultaneous calibration approach.

Pathfinder @ Penn State

Pathfinder @ Penn State

R~40,000 coverage of Y, J, H bands- few orders a time. Fiber slicing/modal noise issues tested

Pathfinder @ Penn State

The Big Issues in Precision NIR RVs

•Detector Issues: NIR detectors not as well characterized for RV work and low noise as CCDs

•Calibration Issues: What wavelength/velocity calibration is best in the NIR?

•Telluric Lines!!!!

•Instrinsic Stellar noise

Solar Light

Th-Ar Lamp

Pathfinder @ Penn State: On ‘Sky’ Performance

Achieve 7-10m/s rms scatter on Sunlight with two different configurations and simultaneous Th-Ar calibration. Suggests detector issues like persistence and parasitic ghosting are not a killer at ~< 10m/s. This is short term stability. Solar daytime observations affected by clouds. Sun not a point source

Ramsey et al. 2008

Also ~6.5m/s stability results presented by Dreizler et al. with CRIRES + gas cell

The Big Issues

Telluric Lines

Calibration & Instrument Tracking

NIR Detectors

The Big Issues: Calibration•Simultaneous Calibration with Th-Ar a logical option since obviously Th-Ar works in the visible to <1m/s

•NIR lineslists of Th-Ar made by Kerber et al 2008 for CRIRES

•No lack of Lines, issue is that Ar lines are much much brighter, and not as stable. Can sub-array readout with an NIR array, but still scattered light

•Frequency comb is certainly useful, but in terms of providing a well spaced grid, not in terms of stability- 1cm/s stability is not needed at the moment in the NIR

•Th lines are stable enough. Issue is the argon/ faint nature of the Th lines. Are there other lamps/sources we can use?

Freq. Comb Steinmetz et al. 2008

The Big Issues

Telluric Lines

Calibration & Instrument Tracking

NIR Detectors

The Big Issues: Calibration•Exploring Other lamps.

Thorium 232Th Uranium 238U

Heavy Element Yes Yes

0 nuclear spin Yes Yes

Long ½ life Yes Yes

Many Lines Yes Yes

Mononucleide Yes NO

(0.7% 235U)

Th/Ar

Th/Ne

U/Ar U/Ne

In parts of the Y band that we have tested these lamps with pathfinder U seems to have significantly more lines than Th, and Ne has fewer than Ar.

Further exploration of U/Ne and effect of 235U to be explored.

Other calibration systems include telecom gas cells for wavelength references, and conventional or fiber Fabry Perots to provide a grid of lines across the spectrum

Mahadevan et al. 2009

NIST Gas cells from Telecom.

Micron optics. Temperature stabilization essential

The Big Issues: Calibration

•The Hobby Eberly Telescope is a 9m optical telescope in McDonald Observatory Texas.

•2012 Wide Field upgrade for the HETDEX will make pupil ~ 10m, significantly increase efficiency, guiding accuracy, mirror phasing etc.

•Post 2012 ONLY fiber fed instruments possible on the HET.

•HET is a non-steerable primary, can only observe objects for ~1hr around airmass 1.35

•Fully queue scheduled, good for spectroscopic surveys like RV monitoring

•The Habitable Zone Planet Finder (HZPF) is a facility class NIR high resolution instrument that we have proposed to the NSF Major Research Instrumentation Program in August 2009

•Derives its Heritage from PRVS/Gemini Study

•Niche Instrument-No moving parts

•Optimized for RVs

•Primary Science Goal is M dwarf planet search

The HZPF on the HET

The HZPF on the HET

Design Concept is a White Pupil Echelle with a ZnSe Grism Cross Disperser. Primary disperser is a 200 x 800mm R4 echelle. Fast f/2 camera. Cooled but not cryogenic. No liquid nitrogen, no K band. Large beam – 150mm diameter. Spectral Resolution R > 50,000

The HZPF on the HET

•Coverage of Y, J and H bands.

•H2RG with 1.7μm cutoff

•LBLN Deep Depletion CCD covers Y to allow cross-comparison of velocities

•Upgrade path in future is a 4k x 4k H4RG-15 (when available), with CCD retired

•Optics designed for wide field to accommodate this path

•3.5px sampling of R~50,000 resolution allows higher resolution if necessary

The HZPF on the HET

•Blue circle- Mike Endl’s ongoing M dwarf program at the HET

•Red circle- from Jenkins et al. 2009, late M dwarfs whose vsini is being meaured with HRS @ HET to build a suitable target list for the HZPF

The HZPF on the HET

Subsystem Component Efficiency

Telescope Primary and SAC 0.750Fibre Feed 1.2’’ seeing 0.650

Fiber 30m 0.895Double Scrambler 0.700

Slit Slit Losses 0.500Spectrograph Order Blocking Filter 0.850

Collimator X 3, 0.993 0.970Echelle 0.700Spectrum mirror 0.990ZnSe Grism 0.700Camera Optics 0.900

Detector Detector QE (J) 0.880

Total 4.8%R>50,000

Efficiency model of the HZPF Instrument in J band

•Will be used to survey ~300 stars at ~1-3m/s, acquiring 20-30 radial velocity points on each stars, and more on anything that looks interesting

•Will likely be a bright time complement to the HET Dark Energy Survey (HETDEX)

•Possibility of sharing the focal plane with HETDEX being explored.

HZPF is a fiber fed NIR spectrograph that we think can meet the recommendation of the ExoPTF within the cost cap of the NSF MRI-R2 proposal. Tradeoffs in Resolution/Efficiency still ongoing. HET is a big fast telescope, making the instrument beam size large as well.

Acknowledge significant heritage, discussion with PRVS & UPF teams!

The Big Issues

Telluric Lines

Calibration & Instrument Tracking

NIR Detectors

The NIR Precision RV spectrographs

•CRIRES with a gas cell on 8m VLT

•T-EDI on 5m Palomar

•PRVS, originally proposed for Gemini, not funded

• HZPF on the HET

• UPF (UKIRT Planet Finder), for UKIRT

•CARMENES for Calar Alto

•NAHUAL for the 10m GTC

•HDU/IRCS for Subaru (Si Immersion Grating)

•WINERED for Subaru ? (ZnSe Immersion Grating)

•SIMPLE for EELT

•FIRST for Apache Point Observatory 3.5 m (Si Immersion Grating)

Combination of gas cell/simultaneous fiber calibration approaches. Wavelength coverage typically subset of 0.85-2.5μm. In various states of proposal/funding, and anticipated times of first light range from 2011-2013

The Big Issues

Telluric Lines

Calibration & Instrument Tracking

NIR Detectors

Summary

•NIR RVs are now < 10m/s from prototypes/initial feasibility tests results, multiple groups attempting to develop cross-dispersed high-resolution NIR spectrographs

•Very important for discovering the low-mass planet population around mid-late M stars, confirming astrometric detection expected in next few years, and confirming candidates from dedicated ground/space based surveys looking at low mass stars.

•Even if transits detected, RVs provide confirmation and mass estimates. Important to have the radius AND mass when attempting to characterize the atmosphere of potential terrestrial planets.

•Synergy with existing optical precision RV to help disentangle stellar activity from planetary signals.

•Pathfinder setup to explore issues and possible solutions to <3m/s in the NIR, which will feed into development of the HZPF on the HET