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Title: EXO-ZODI MODELING FOR THE LARGE BINOCULAR TELESCOPE INTERFEROMETER

Abstract

Habitable zone dust levels are a key unknown that must be understood to ensure the success of future space missions to image Earth analogs around nearby stars. Current detection limits are several orders of magnitude above the level of the solar system's zodiacal cloud, so characterization of the brightness distribution of exo-zodi down to much fainter levels is needed. To this end, the Large Binocular Telescope Interferometer (LBTI) will detect thermal emission from habitable zone exo-zodi a few times brighter than solar system levels. Here we present a modeling framework for interpreting LBTI observations, which yields dust levels from detections and upper limits that are then converted into predictions and upper limits for the scattered light surface brightness. We apply this model to the HOSTS survey sample of nearby stars; assuming a null depth uncertainty of 10{sup –4} the LBTI will be sensitive to dust a few times above the solar system level around Sun-like stars, and to even lower dust levels for more massive stars.

Authors:
; ; ;  [1]; ; ; ; ; ;  [2]; ; ; ;  [3]; ; ;  [4];  [5];  [6];  [7] more »; « less
  1. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  2. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  3. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
  4. NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics, Code 667, Greenbelt, MD 20771 (United States)
  5. Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
  6. Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)
  7. NASA Exoplanet Science Institute, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22340092
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 216; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; COSMIC DUST; IMAGES; INTERFEROMETERS; SENSITIVITY; SIMULATION; SOLAR SYSTEM; SUN; TELESCOPES; VISIBLE RADIATION

Citation Formats

Kennedy, Grant M., Wyatt, Mark C., Panić, Olja, Shannon, Andrew, Bailey, Vanessa, Defrère, Denis, Hinz, Philip M., Rieke, George H., Skemer, Andrew J., Su, Katherine Y. L., Bryden, Geoffrey, Mennesson, Bertrand, Morales, Farisa, Serabyn, Eugene, Danchi, William C., Roberge, Aki, Stapelfeldt, Karl R., Haniff, Chris, Lebreton, Jérémy, Millan-Gabet, Rafael, and and others. EXO-ZODI MODELING FOR THE LARGE BINOCULAR TELESCOPE INTERFEROMETER. United States: N. p., 2015. Web. doi:10.1088/0067-0049/216/2/23.
Kennedy, Grant M., Wyatt, Mark C., Panić, Olja, Shannon, Andrew, Bailey, Vanessa, Defrère, Denis, Hinz, Philip M., Rieke, George H., Skemer, Andrew J., Su, Katherine Y. L., Bryden, Geoffrey, Mennesson, Bertrand, Morales, Farisa, Serabyn, Eugene, Danchi, William C., Roberge, Aki, Stapelfeldt, Karl R., Haniff, Chris, Lebreton, Jérémy, Millan-Gabet, Rafael, & and others. EXO-ZODI MODELING FOR THE LARGE BINOCULAR TELESCOPE INTERFEROMETER. United States. doi:10.1088/0067-0049/216/2/23.
Kennedy, Grant M., Wyatt, Mark C., Panić, Olja, Shannon, Andrew, Bailey, Vanessa, Defrère, Denis, Hinz, Philip M., Rieke, George H., Skemer, Andrew J., Su, Katherine Y. L., Bryden, Geoffrey, Mennesson, Bertrand, Morales, Farisa, Serabyn, Eugene, Danchi, William C., Roberge, Aki, Stapelfeldt, Karl R., Haniff, Chris, Lebreton, Jérémy, Millan-Gabet, Rafael, and and others. Sun . "EXO-ZODI MODELING FOR THE LARGE BINOCULAR TELESCOPE INTERFEROMETER". United States. doi:10.1088/0067-0049/216/2/23.
@article{osti_22340092,
title = {EXO-ZODI MODELING FOR THE LARGE BINOCULAR TELESCOPE INTERFEROMETER},
author = {Kennedy, Grant M. and Wyatt, Mark C. and Panić, Olja and Shannon, Andrew and Bailey, Vanessa and Defrère, Denis and Hinz, Philip M. and Rieke, George H. and Skemer, Andrew J. and Su, Katherine Y. L. and Bryden, Geoffrey and Mennesson, Bertrand and Morales, Farisa and Serabyn, Eugene and Danchi, William C. and Roberge, Aki and Stapelfeldt, Karl R. and Haniff, Chris and Lebreton, Jérémy and Millan-Gabet, Rafael and and others},
abstractNote = {Habitable zone dust levels are a key unknown that must be understood to ensure the success of future space missions to image Earth analogs around nearby stars. Current detection limits are several orders of magnitude above the level of the solar system's zodiacal cloud, so characterization of the brightness distribution of exo-zodi down to much fainter levels is needed. To this end, the Large Binocular Telescope Interferometer (LBTI) will detect thermal emission from habitable zone exo-zodi a few times brighter than solar system levels. Here we present a modeling framework for interpreting LBTI observations, which yields dust levels from detections and upper limits that are then converted into predictions and upper limits for the scattered light surface brightness. We apply this model to the HOSTS survey sample of nearby stars; assuming a null depth uncertainty of 10{sup –4} the LBTI will be sensitive to dust a few times above the solar system level around Sun-like stars, and to even lower dust levels for more massive stars.},
doi = {10.1088/0067-0049/216/2/23},
journal = {Astrophysical Journal, Supplement Series},
number = 2,
volume = 216,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 2015},
month = {Sun Feb 01 00:00:00 EST 2015}
}
  • The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high angular resolution and high-contrast infrared imaging (1.5–13 μ m). In this paper, we focus on the mid-infrared (8–13 μ m) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in 2015 March. With an interferometric baseline of 14.4 m, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to preparemore » for future exo-Earth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in 2015 February a calibrated null accuracy of 0.05% over a 3 hr long observing sequence on the bright nearby A3V star β Leo. This is equivalent to an exozodiacal disk density of 15–30 zodi for a Sun-like star located at 10 pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.« less
  • We identify and phase a sample of 107 Cepheids with 10 days < P < 100 days in M81 using the Large Binocular Telescope and calibrate their B, V, and I mean magnitudes with archival Hubble Space Telescope (HST) data. The use of a ground-based telescope to identify and phase the Cepheids and HST only for the final calibration reduces the demand on this highly oversubscribed spacecraft by nearly an order of magnitude and yields period-luminosity (PL) relations with dispersions comparable to the best LMC samples. We fit the sample using the OGLE-II LMC PL relations and are unable tomore » find a self-consistent distance for different band combinations or radial locations within M81. We can do so after adding a radial dependence to the PL zero point that corresponds to a luminosity dependence on metallicity of {gamma}{sub {mu}} = -0.56 {+-} 0.36 mag dex{sup -1}. We find marginal evidence for a shift in color as a function of metallicity, distinguishable from the effects of extinction, of {gamma}{sub 2} = +0.07 {+-} 0.03 mag dex{sup -1}. We find a distance modulus for M81, relative to the LMC, of {mu}{sub M81} - {mu}{sub LMC} = 9.39 {+-} 0.14 mag, including uncertainties due to the metallicity corrections. This corresponds to a distance to M81 of 3.6 {+-} 0.2 Mpc, assuming an LMC distance modulus of 18.41 mag. We carry out a joint analysis of M81 and NGC 4258 Cepheids and simultaneously solve for the distance of M81 relative to NGC 4258 and the metallicity corrections. Given the current data, the uncertainties of such joint fits are dominated by the relative metallicities and the abundance gradients rather than by measurement errors of the Cepheid magnitudes or colors. We find {mu}{sub M81} - {mu}{sub LMC} = 9.40{sup +0.15}{sub -0.11} mag, {mu}{sub N4258} - {mu}{sub LMC} = 11.08{sup +0.21}{sub -0.17} mag, and {mu}{sub N4258} - {mu}{sub M81} = 1.68 {+-} 0.08 mag and metallicity effects on luminosity and color of {gamma}{sub {mu}} = -0.62{sup +0.31}{sub -0.35} mag dex{sup -1} and {gamma}{sub 2} = 0.01 {+-} 0.01 mag dex{sup -1}. Quantitative analyses of Cepheid distances must take into account both the metallicity dependencies of the Cepheids and the uncertainties in the abundance estimates.« less
  • We used the near-IR imager/spectrograph LUCIFER mounted on the Large Binocular Telescope to image, with subarcsecond seeing, the local dwarf starburst NGC 1569 in the JHK bands and He I 1.08 {mu}m, [Fe II] 1.64 {mu}m, and Br{gamma} narrowband filters. We obtained high-quality spatial maps of He I 1.08 {mu}m, [Fe II] 1.64 {mu}m, and Br{gamma} emission across the galaxy, and used them together with Hubble Space Telescope/Advanced Camera for Surveys images of NGC 1569 in the H{alpha} filter to derive the two-dimensional spatial map of the dust extinction and surface star formation rate (SFR) density. We show that dustmore » extinction (as derived from the H{alpha}/Br{gamma} flux ratio) is rather patchy and, on average, higher in the northwest (NW) portion of the galaxy (E{sub g}(B - V) {approx_equal} 0.71 mag) than in the southeast (E{sub g}(B - V) {approx_equal} 0.57 mag). Similarly, the surface density of SFR (computed from either the dereddened H{alpha} or dereddened Br{gamma} image) peaks in the NW region of NGC 1569, reaching a value of about 4 x 10{sup -6} M{sub sun} yr{sup -1} pc{sup -2}. The total SFR as estimated from the integrated, dereddened H{alpha} (or, alternatively, Br{gamma}) luminosity is about 0.4 M{sub sun} yr{sup -1}, and the total supernova rate from the integrated, dereddened [Fe II] 1.64 {mu}m luminosity is about 0.005 yr{sup -1} (assuming a distance of 3.36 Mpc). The azimuthally averaged [Fe II] 1.64 {mu}m/Br{gamma} flux ratio is larger at the edges of the central, gas-deficient cavities (encompassing the superstar clusters A and B) and in the galaxy outskirts. If we interpret this line ratio as the ratio between the average past star formation (as traced by supernovae) and ongoing activity (represented by OB stars able to ionize the interstellar medium), it would then indicate that star formation has been quenched within the central cavities and lately triggered in a ring around them. The number of ionizing hydrogen and helium photons as computed from the integrated, dereddened H{alpha} and He I 1.08 {mu}m luminosities suggests that the latest burst of star formation occurred about 4 Myr ago and produced new stars with a total mass of {approx_equal}1.8 x 10{sup 6} M{sub sun}.« less
  • We present near-infrared multi-object spectroscopy and JHK{sub s} imaging of the massive stellar content of the Galactic star-forming region W3 Main, obtained with LUCI at the Large Binocular Telescope. We confirm 15 OB stars in W3 Main and derive spectral types between O5V and B4V from their absorption line spectra. Three massive young stellar objects are identified by their emission line spectra and near-infrared excess. The color-color diagram of the detected sources allows a detailed investigation of the slope of the near-infrared extinction law toward W3 Main. Analysis of the Hertzsprung-Russell diagram suggests that the Nishiyama extinction law fits themore » stellar population of W3 Main best (E(J - H)/E(H - K{sub s}) = 1.76 and R{sub K{sub s}} = 1.44). From our spectrophotometric analysis of the massive stars and the nature of their surrounding H II regions, we derive the evolutionary sequence of W3 Main and we find evidence of an age spread of at least 2-3 Myr. While the most massive star (IRS2) is already evolved, indications for high-mass pre-main-sequence evolution are found for another star (IRS N1), deeply embedded in an ultracompact H II (UCH II) region, in line with the different evolutionary phases observed in the corresponding H II regions. We derive a stellar mass of W3 Main of (4 {+-} 1) Multiplication-Sign 10{sup 3} M{sub Sun} by extrapolating from the number of OB stars using a Kroupa initial mass function and correcting for our spectroscopic incompleteness. We have detected the photospheres of OB stars from the more evolved diffuse H II region to the much younger UCH II regions, suggesting that these stars have finished their formation and cleared away their circumstellar disks very fast. Only in the hyper-compact H II region (IRS5) do the early-type stars seem to be still surrounded by circumstellar material.« less
  • We show that the candidate progenitor of the core-collapse SN 2011dh in M 51 (8 Mpc away) was fading by 0.039 {+-} 0.006 mag yr{sup -1} during the 3 years prior to the supernova, and that this level of variability is moderately unusual for other similar stars in M 51. While there are uncertainties about whether the true progenitor was a blue companion to this candidate, the result illustrates that there are no technical challenges to obtaining fairly high precision light curves of supernova-progenitor systems using ground-based observations of nearby (<10 Mpc) galaxies with wide-field cameras on 8 m classmore » telescopes. While other sources of variability may dominate, it is even possible to reach into the range of evolution rates required by the quasi-static evolution of the stellar envelope. For M 81, where we have many more epochs and a slightly longer time baseline, our formal 3{sigma} sensitivity to slow changes is presently 3 mmag yr{sup -1} for an M{sub V} {approx_equal} -8 mag star. In short, there is no observational barrier to determining whether the variability properties of stars in their last phases of evolution (post-carbon ignition) are different from earlier phases.« less