2006: Colby Jurgenson completed his PhD in Aug.2005 and moved to a postdoc position at New Mexico Tech with the Magdalena Ridge project. The future of the equipment is open to inquiries. For status, see: Link to SIFTIR abstract
Persons interested in collaborating
observationally with this NSF-sponsored camera are invited to contact
rstencel@du.edu.
Paper based on TNTCAM2 results: "Mid IR polarimetry of NGC 7027" by
Jurgenson, Stencel, Klebe and Theil, 2003 ApJ Letters 582: L35. [Link to pdf
SIFTIR updates: email cjurgens at du.edu
See also: conference Proceeding papers: ASTRONOMICAL POLARIMETRY
[Waikoloa, March 2004], and HIGH RES ASTRONOMICAL SPECTROSCOPY, ESO
Workshop [Garching, 2003].
An important recent paper about mid-IR spectro-polarimetry appears in
Monthly Notices, vol. 312, p.327, C.Smith et al.
======================================================================== 2004Jun.01 Please email comments to rstencel@du.edu Page = http://www.du.edu/~rstencel/MtEvans/TNTCAM2.htm ======================================================================== PRESENT SCHEDULE (* new items): ------------------------------------------------------------------------ NEXT OBSERVING RUN(s): TBA/SAL 2004-- August, LABVIEW control of interferometer and IR array achieved. 2003-- decision to rebuild SIFTIR operating system and array control under LABVIEW as part of Jurgenson thesis effort. 2002-- data analysis of WIRO run leading to NGC 7027 publication [ApJL] TNTCAM archive info: 2001-- WIRO obs time request status (watch us at site 179.72.213.8): D. Fri.Jun.1-Wed.Jun.6 (with AAS meeting remote observing) E. Sun.Jun.17-Thu,Jun.21 w/High school outreach F. Sat.Jul.28-Thu.Aug.2 "( & possible extension for engineering) G. tentatively Oct. TECHNOLOGY ISSUES: 256x256 array -- finally rcvd Nov.2000 Original PO placed 12/99 for 3/2000 delivery! Update Sept.2000: 2400 e read noise, and a 'few dead pixel islands' June'01: cabling and parts fab nearly done for drop in test at WIRO & preliminary polarimetry data reduction pipeline processor built. New chip carrier -- DST says we can design and build in 3 months (< 1/1/01) Electronics and software -- *new electronix have cabling issues/Bean build new for next run *need to reinstall com card on Wally1 and offload March type 1 data W1 battery problem... filter drivers/port comm and GUI developments (ME) major progress with TCL and gui's :) Optics -- Replacement wire grids ordered, Molectron PO94207, 5/1/00, 5 wks (CJ) Received 5/19, installed 6/15/00 Replacement ZnSe reimaging lens on order and installed 9/00 Cryogen status -- LHe need to order by Fri a.m. for following Tues LN2 can be delivered 2-3 days ARO -- Kathy x3486 PROPOSALS AND PAPERS: AAS POSTER PAPER June2001 (5.06) Early Results from TNTCAM2, a Mid-IR Imaging Polarimeter, and Remote Internet Observing -- D. S. Theil, M. E. Edwards, C. A. Jurgenson, D. I. Klebe, R. E. Stencel (University of Denver, Department of Physics and Astronomy), J. L. Cash, R. T. Martin, P. E. Johnson, J. S. Weger (University of Wyoming,) We present new science results from TNTCAM2 obtained at the WIRO 2.3 meter telescope. These include: (1) polarization maps of the BN object and a section of M42 around the Trapezium that shows bow shocks; (2) imaging and polarimetry of selected circumstellar shells of evolved stars and planetary nebulae; (3) new mid-IR photometry of ISO selected Vega-type stars showing a mid-infrared spectral energy excess, and (4) attempts to detect proplyds in Orion. Proposals due: 31 August 2000: submitted, NSF ATI-Advanced Technologies&Instrumentation http://www.nsf.gov/mps/ast/facility.htm#ati MID IR SURVEY OF POLARIZED IMBEDDED SOURCES IN STAR FORMING REGIONS D.S.Theil, P.I., D.I.Klebe & R.E.Stencel, Co-Is, UWyo & EI? collabs. Papers in preparation: DTheil's PhD thesis! "Practise defnese" 8/23/00, next try TBD JSudol's PhD thesis! This includes some of the first 1-D visibility data obtained from array images at mid-IR wavelengths of red giant and super- giant stars like alpha Ori, VY CMa, chi Cyg, IRC10216, IK Tau, NML Cyg, mu Cep, IRC10420, o Cet, TX Cam, R Cas and CIT 3. RECENT OBSERVING RUNS: "Winter/Spring 2001 TNTCAM Multiweek Marathon" A. Mon.Jan.15 - Wed.Jan.24 weather and instrument problems B. Mon.Feb.5 - Wed.Feb.14 good polarimetry and some bad weather C. Wed.Mar.7 - Fri.Mar.16 good polarimetry 4-8 Dec.2000, WIRO: 750Mb data, very successful run, Craig Smith co-obs. 12-16 Oct.2000, WIRO, moderately successful polarim, but poor weather 18-22 June 2000, WIRO, polarimetry and imaging, esp. SFRs like W51 *plus 2 high school participants & Jessica Reynolds March, 2000 WIRO: FIRST LIGHT, polarimetry mode, data reduction showed problems with IROBS version (1.41) of fitswrite (www.cs.wisc.edu/~mkeller/publish.html). lead to bugfix vers.1.43 Oct'99 WIRO -- detector problems, resolved with degreasing chip holder May'99: First light, imaging mode, IRTF (Galileo and Mars opp.) data delivered on CDROMs to JPL for analysis Spring 1999 -- cryostat testing, detector and filter installation completed in time to support an IRTF run for Galileo-Callisto encounter. Jan/Feb 1999 -- TNTCAM1.5 observing run at IRTF, Galileo encounter support. CALIBRATION DATA SOURCES: -------------------Some useful websites------------------------------------ http://irtf.ifa.hawaii.edu/IRrefdata/ph_catalogs.html http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/ http://www.jach.hawaii.edu/JACpublic/UKIRT/instruments/irpol/irpol_stds.html --------------------------------------------------------------------------- During the preparation and execution of the European Space Agency's Infrared Space Observatory (ISO) mission extensive programmes were conducted to establish catalogues of celestial calibration standards adequate to support the calibration needs of the mission. These programmes have led, in particular, to the production of sets of stellar, asteroidal and planetary calibration sources - both photometric and spectral, often spanning the full 2.5 to 240 micron wavelength range of ISO. We would like to draw your attention to this, now publicly available, database of near to far-infrared calibration sources, which you can find - along with comprehensive explanatory and reference material, at: http://www.iso.vilspa.esa.es/users/expl_lib/ISO/wwwcal/ We hope that the astronomical community will find these products of the ISO mission useful in a wide range of applications. ---------------------------------------------------------------------------
This camera can contribute to the understanding of YSOs and evolved stars, obtaining high resolution mid-IR observations of dusty environments immediately surrounding these objects. In ordinary imaging mode mosaics of extended objects can be made in 2x2 arcmin intervals. In polarimetry mode, assuming adequate grain alignment timescales, magnetic fields in YSOs can be probed by dust emission from hot cores. The camera can better constrain grain alignment scenarios in young stellar environments.
Emission (rather than scattering) dominates signal at mid-IR wavelengths, allowing determination of grain alignment in a source. This enables distinction between models explaining near-IR polarization seen in dust shells surrounding late red giants, i.e. scattering from asymmetric shells or aligned grains.
There are no mid-IR array polarimeters in operation. In polarimetry mode, TNTCAM II will be sensitive to linear polarizations as small as 0.2\%. We have chosen the simple approach of imaging one state at a time and modulating polarization at a frequency high enough to remove atmospheric and system noise fluctuations. Dewar design and the optical system are discussed, including the pros and cons of rotating waveplates or an Abbe-Konig "K"-mirror to modulate the polarization, and the use of a rotating window assembly allowing on-the-fly f-ratio adjustment and observation across the entire 5-25$\mu$m band. We acknowledge support under NSF grant AST-9724506 to the University of Denver.
We considered using a "K"-mirror to rotate the plane of polarization of the beam, instead of transmissive bi-refringent materials but found that the precise optical alignment these devices require to be prohibitive, in addition to creating significant difficulties in image processing. The exclusive use of transmissive optics allows us to have an on-axis system avoiding some instrumental polarization effects and minimizing optical aberrations.
The optical waveplate and filter wheels will be rotated by special low temperature stepper motors in the Helium dewar. This minimizes the heat load from mechanical feed throughs. Along with a relatively large He dewar (3.5 to 4 liters) we anticipate cryogen holding times in excess of 24 hours.
Finally, this is the only known ground-based polarimeter in the 10-20 micron region. It will be an invaluable support instrument to missions like SIRTF and will be the only instrument in the world that able to carry out certain kinds of experiments.
STAR AND PLANET FORMING REGIONS:
This camera can contribute to the understanding of YSOs and
evolved stars, obtaining high resolution mid-IR observations of
dusty environments immediately surrounding these objects. In
ordinary imaging mode mosaics of extended objects can be made
in 2x2 arcmin intervals. In polarimetry mode, assuming adequate
grain alignment timescales, magnetic fields in YSOs can be
probed by dust emission from hot cores. The camera can better
constrain grain alignment scenarios in young stellar
environments.
The standard model for star formation (Adams, Shu and Lada 1987) includes a disk phase that admits the possibility of planet formation. While the entire protostar phase is estimated to persist only a few millions of years, the planet-forming processes in the associated disk span up to a billion years, include a diversity of dynamics and solid state chemical physics that defy easy model-making. Hence, we are heavily dependent on observational clues that define the evolutionary changes leading to success or failure in manufacture of planetary systems around young stars.
IRAS provided a breakthru in the study of planet-forming physics with the discovery that ordinary main sequence stars possess excesses in their far infrared spectral energy distribution (Aumann et al. 1984; see also Backman and Paresce, 1993). Surveys of large numbers of normal stars, such as 5706 SAO stars by Stencel and Backman (1991), reveals that IRAS detected far-IR excesses in up to 10 percent of main sequence stars, to the limits of IRAS sensitivity. These surveys are currently being extended under several ISO Key Projects by Habing, Becklin, Stencel and others, but preliminary results are consistent with IRAS findings.
However, except for the spectacular case of beta Pictoris (and more recently BD+31 643 and Orion nebula "proplyds"), these infrared excesses, interpreted as protoplanetary disks, have defied detection at non-infrared wavelengths. Hence, mid-infrared imaging and polarimetry offer the ideal method of examining the structure of these disks in detail, in order to explore the 50K material in the regions analogous to our solar system's Kuiper Belt. Observations with the 3 x 3 mid IR array on ISO (PHOT C100) have revealed the extent of disk material surrounding alpha PsA (Fajardo, Stencel and Backman 1997), but the limited 15 arcsec resolution provides only 2-3 pixels of definition for this nearby source.
TNTCAM2 will greatly exceed ISOPHOT's performance in spatial resolution and flux sensitivity. Maps like that for alpha PsA will be better resolved by factors of 5, providing greater spatial resolution across the 100 to 1000 AU regions surrounding the central star. Density profiles and polarization vectors will constrain collisional population of this portion of the protoplanetary disk, and help to establish evolutionary changes among disks around many nearby main sequence stars identified to have disks by IRAS and ISO. TNTCAM2 can make a major contribution to this research and prepare SIRTF/SOFIA observational assaults for maximum productivity.
EVOLVED STARS AND PLANETARY NEBULAE:
Emission (rather than scattering) dominates signal at mid-IR
wavelengths, allowing determination of grain alignment in a
source. This enables distinction between models explaining
near-IR polarization seen in dust shells surrounding late red
giants, i.e. scattering from asymmetric shells or aligned grains.
The stellar mass loss impacts the chemical evolution of the Galaxy. Evolved stars of all masses exhibit evidence for enhanced mass loss, and in many cases, dust formation. The precise physics of the process is still under debate, but mass loss rates can briefly compete with nuclear timescales in radically altering the star's outer structure. This leads to extended circumstellar shells, as detected even with the low spatial resolution (2.3 arcminutes) of IRAS at 60 microns (Stencel, Pesce and Bauer 1989; Bauer and Stencel, 1994; Young et al. 1993). The shells require tens of thousands of years to fill at slow stellar wind speeds, and are implicated in structuring the light echoes and rings observed in supernova remnants like that of SN 1987A in the LMC (Chevalier and Fransson 1994). Mid-IR imaging has begun to detect the inner portions of these evolved star shells at the arcsecond spatial scale, but TNTCAM2 can contribute direct spatial imaging and polarimetry of the cold shell characteristics.