Calibration of the Tip of the Red Giant Branch (TRGB). (arXiv:2002.01550v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Freedman_W/0/1/0/all/0/1">Wendy L. Freedman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Madore_B/0/1/0/all/0/1">Barry F. Madore</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoyt_T/0/1/0/all/0/1">Taylor Hoyt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jang_I/0/1/0/all/0/1">In Sung Jang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beaton_R/0/1/0/all/0/1">Rachael Beaton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_M/0/1/0/all/0/1">Myung Gyoon Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monson_A/0/1/0/all/0/1">Andrew Monson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neeley_J/0/1/0/all/0/1">Jill Neeley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rich_J/0/1/0/all/0/1">Jeffrey Rich</a>
The Tip of the Red Giant (TRGB) method provides one of the most accurate and
precise means of measuring the distances to nearby galaxies. Here we present a
VIJHK absolute calibration of the TRGB based on observations of TRGB stars in
the Large Magellanic Cloud (LMC),grounded on detached eclipsing binaries
(DEBs). This paper presents a more detailed description of the method first
presented in Freedman et al. (2019) for measuring corrections for the total
line-of-sight extinction and reddening to the LMC. In this method, we use a
differential comparison of the red giant population in the LMC, first with red
giants in the Local Group galaxy, IC 1613, and then with those in the Small
Magellanic Cloud. As a consistency check, we derive an independent calibration
of the TRGB sequence using the SMC alone, invoking its geometric distance also
calibrated by DEBs. An additional consistency check comes from near-infrared
observations of Galactic globular clusters covering a wide range of
metallicities. In all cases we find excellent agreement in the zero-point
calibration. We then examine the recent claims by Yuan et al. (2019),
demonstrating that, in the case of the SMC, they corrected for extinction alone
while neglecting the essential correction for reddening as well. In the case of
IC 1613, we show that their analysis contains an incorrect treatment of
(over-correction for) metallicity. Using our revised (and direct) measurement
of the LMC TRGB extinction, we find a value of Ho = 69.6 +/-0.8 (+/-1.1% stat)
+/- 1.7 (+/-2.4% sys) km/s/Mpc.
The Tip of the Red Giant (TRGB) method provides one of the most accurate and
precise means of measuring the distances to nearby galaxies. Here we present a
VIJHK absolute calibration of the TRGB based on observations of TRGB stars in
the Large Magellanic Cloud (LMC),grounded on detached eclipsing binaries
(DEBs). This paper presents a more detailed description of the method first
presented in Freedman et al. (2019) for measuring corrections for the total
line-of-sight extinction and reddening to the LMC. In this method, we use a
differential comparison of the red giant population in the LMC, first with red
giants in the Local Group galaxy, IC 1613, and then with those in the Small
Magellanic Cloud. As a consistency check, we derive an independent calibration
of the TRGB sequence using the SMC alone, invoking its geometric distance also
calibrated by DEBs. An additional consistency check comes from near-infrared
observations of Galactic globular clusters covering a wide range of
metallicities. In all cases we find excellent agreement in the zero-point
calibration. We then examine the recent claims by Yuan et al. (2019),
demonstrating that, in the case of the SMC, they corrected for extinction alone
while neglecting the essential correction for reddening as well. In the case of
IC 1613, we show that their analysis contains an incorrect treatment of
(over-correction for) metallicity. Using our revised (and direct) measurement
of the LMC TRGB extinction, we find a value of Ho = 69.6 +/-0.8 (+/-1.1% stat)
+/- 1.7 (+/-2.4% sys) km/s/Mpc.
http://arxiv.org/icons/sfx.gif
