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Hatt, Dylan,Freedman, Wendy L.,Madore, Barry F.,Beaton, Rachael L.,Hoyt, Taylor J.,Jang, In Sung,Lee, Myung Gyoon,Monson, Andrew J.,Rich, Jeffrey A.,Scowcroft, Victoria,Seibert, Mark American Astronomical Society 2018 The Astrophysical journal Vol.861 No.2
<P>The Carnegie-Chicago Hubble Program is undertaking a re-calibration of the extragalactic distance scale, using SNe Ia that are tied to Tip of the Red Giant Branch (TRGB) distances to local galaxies. We present here deep Hubble Space Telescope ACS/WFC imaging of the resolved stellar populations in the metal-poor halos of the SN. Ia-host galaxies NGC 4424, NGC 4526, and NGC 4536. These three Virgo constellation galaxies are prime targets for calibrating the extragalactic distance scale given their relative proximity in the local universe and their low line-of-sight reddenings. Anchoring the TRGB zero-point to the geometric distance to the Large Magellanic Cloud via detached eclipsing binaries, we measure extinction-corrected distance moduli of 31.00 +/- 0.03(stat) +/- 0.06(sys) mag, 30.98 +/- 0.03(stat) +/- 0.06(sys) mag, and 30.99 +/- 0.03(stat) +/- 0.06(sys) mag for NGC 4424, NGC 4526, and NGC 4536, respectively, or 15.8 +/- 0.2(stat) +/- 0.4(sys) Mpc, 15.7 +/- 0.2(stat) +/- 0.4(sys) Mpc, and 15.8. +/-. 0.2stat. +/-. 0.4sys Mpc. For these three galaxies, the distances are the first that are based on the TRGB, and for NGC 4424 and NGC 4526, they are the highest-precision distances published to date, each measured to 3%. Finally, we report good agreement between our TRGB distances and the available Cepheid distances for NGC 4424 and NGC 4536, demonstrating consistency between the distance scales currently derived from stars of Population I and II.</P>
Hatt, Dylan,Beaton, Rachael L.,Freedman, Wendy L.,Madore, Barry F.,Jang, In-Sung,Hoyt, Taylor J.,Lee, Myung Gyoon,Monson, Andrew J.,Rich, Jeffrey A.,Scowcroft, Victoria,Seibert, Mark American Astronomical Society 2017 The Astrophysical Journal Vol.845 No.2
<P>IC 1613 is an isolated dwarf galaxy within the Local Group. Low foreground and internal extinction, low metallicity, and low crowding make it an invaluable testbed for the calibration of the local distance ladder. We present new, high-fidelity distance estimates to IC 1613 via its Tip of the Red Giant Branch (TRGB) and its RR Lyrae (RRL) variables as part of the Carnegie-Chicago Hubble Program, which seeks an alternate local route to H-0 using Population II stars. We have measured a TRGB magnitude I-ACS(TRGB) = 20.35 +/- 0.01(stat) +/- 0.01(sys) mag using wide-field observations obtained from the IMACS camera on the Magellan-Baade telescope. We have further constructed optical and near-infrared RRL light curves using archival BI-and new H-band observations from the ACS/WFC and WFC3/IR instruments on board the Hubble Space Telescope (HST). In advance of future Gaia data releases, we set provisional values for the TRGB luminosity via the Large Magellanic Cloud and Galactic RRL zero-points via HST parallaxes. We find corresponding true distance moduli mu(TRGB)(0) = 24.30 +/- 0.03(stat) +/- 0.05(sys) mag and mu(RRL)(0) 24.28 +/- 0.04(stat+sys) mag. We compare our results to a body of recent publications on IC 1613 and find no statistically significant difference between the distances derived from Population. I and II stars.</P>
Jang, In Sung,Hatt, Dylan,Beaton, Rachael L.,Lee, Myung Gyoon,Freedman, Wendy L.,Madore, Barry F.,Hoyt, Taylor J.,Monson, Andrew J.,Rich, Jeffrey A.,Scowcroft, Victoria,Seibert, Mark American Astronomical Society 2018 The Astrophysical journal Vol.852 No.1
<P>The Carnegie-Chicago Hubble Program (CCHP) seeks to anchor the distance scale of Type la supernovae via the Tip of the Red Giant Branch (TRGB) method. Based on deep Hubble Space Telescope ACS/WFC imaging, we present an analysis of the TRGB for the metal-poor halo of NGC 1365, a giant spiral galaxy in the Fornax cluster that was host to the Type la supernova SN 2012fr. We have measured the extinction-corrected TRGB magnitude of NGC 1365 to be F814W = 27.34 +/- 0.03(stat) +/- 0.04(sys) mag. In advance of future direct calibration by Gala, we adopt a provisiona I-band TRGB luminosity set at the Large Magellanic Cloud and find a true distance modulus mu(0) = 31.29 +/- 0.04(stat) +/- 0.06(sys) mag or D = 18.1 +/- 0.3(stat) +/- 0.5(sys) Mpc. This measurement is in excellent agreement with recent Cepheid-based distances to NGC 1365 and reveals no significant difference in the distances derived from stars of Populations I and II for this galaxy. We revisit the error budget for the CCHP path to the Hubble constant based on the analysis presented here, i.e., that for one of the most distant Type la supernova hosts within our Program, and find that a 2.5% measurement is feasible with the current sample of galaxies and TRGB absolute calibration.</P>
The Near-infrared Tip of the Red Giant Branch. I. A Calibration in the Isolated Dwarf Galaxy IC 1613
Madore, Barry F.,Freedman, Wendy L.,Hatt, Dylan,Hoyt, Taylor J.,Monson, Andrew J.,Beaton, Rachael L.,Rich, Jeffrey A.,Jang, In Sung,Lee, Myung Gyoon,Scowcroft, Victoria,Seibert, Mark American Astronomical Society 2018 The Astrophysical journal Vol.858 No.1
Interplay of Octahedral Tilts and Polar Order in BiFeO<sub>3</sub> Films
Kim, Young‐,Min,Kumar, Amit,Hatt, Alison,Morozovska, Anna N.,Tselev, Alexander,Biegalski, Michael D.,Ivanov, Ilya,Eliseev, Eugene A.,Pennycook, Stephen J.,Rondinelli, James M.,Kalinin, Sergei V. WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.17
<P><B>Heterointerface stabilization of a distinct nonpolar BiFeO<SUB>3</SUB> phase</B> occurs simultaneously with changes in octahedral tilts. The resulting phase arises via suppression of polarization by a structural order parameter and can thus be identified as anti‐ferroelectric (Fe displacements – bottom panel). The phase is metastable and can be switched into a polar ferroelectric state (top panel) under an applied electric bias.</P>
Beaton, Rachael L.,Freedman, Wendy L.,Madore, Barry F.,Bono, Giuseppe,Carlson, Erika K.,Clementini, Gisella,Durbin, Meredith J.,Garofalo, Alessia,Hatt, Dylan,Jang, In Sung,Kollmeier, Juna A.,Lee, Myun American Astronomical Society 2016 The Astrophysical journal Vol.832 No.2
<P>We present an overview of the Carnegie-Chicago Hubble Program, an ongoing program to obtain a 3% measurement of the Hubble constant (H-0) using alternative methods to the traditional Cepheid distance scale. We aim to establish a completely independent route to H-0 using RR Lyrae variables, the tip of the red giant branch (TRGB), and Type Ia supernovae (SNe Ia). This alternative distance ladder can be applied to galaxies of any Hubble type, of any inclination, and, using old stars in low-density environments, is robust to the degenerate effects of metallicity and interstellar extinction. Given the relatively small number of SNe. Ia host galaxies with independently measured distances, these properties provide a great systematic advantage in the measurement of H-0 via the distance ladder. Initially, the accuracy of our value of H-0 will be set by the five Galactic RR Lyrae calibrators with Hubble Space Telescope Fine-Guidance Sensor parallaxes. With Gaia, both the RR Lyrae zero-point and TRGB method will be independently calibrated, the former with at least an order of magnitude more calibrators and the latter directly through parallax measurement of tip red giants. As the first end-to-end 'distance ladder' completely independent of both Cepheid variables and the Large Magellanic Cloud, this path to H-0 will allow for the high-precision comparison at each rung of the traditional distance ladder that is necessary to understand tensions between this and other routes to H-0.</P>