J/ApJ/896/L43 Cepheids HST amplitudes in V- and H-band (Riess+, 2020)
The accuracy of the Hubble constant measurement verified through Cepheid
amplitudes.
Riess A.G., Yuan W., Casertano S., Macri L.M., Scolnic D.
<Astrophys. J., 896, L43 (2020)>
=2020ApJ...896L..43R 2020ApJ...896L..43R
ADC_Keywords: Photometry, HST ; Stars, variable; Galaxies, nearby;
Photometry, infrared; Optical
Keywords: Cepheid distance ; Hubble constant ; Cosmology ; Distance indicators ;
CCD photometry ; Light curves ; Cepheid variable stars
Abstract:
The accuracy of the Hubble constant measured with extragalactic
Cepheids depends on robust photometry and background estimation in the
presence of stellar crowding. The conventional approach accounts for
crowding by sampling backgrounds near Cepheids and assuming that they
match those at their positions. We show a direct consequence of
crowding by unresolved sources at Cepheid sites is a reduction in the
fractional amplitudes of their light curves. We use a simple
analytical expression to infer crowding directly from the light curve
amplitudes of >200 Cepheids in three Type Ia supernovae hosts and
NGC4258 as observed by Hubble Space Telescope-the first near-infrared
amplitudes measured beyond the Magellanic Clouds. Where local crowding
is minimal, we find near-infrared amplitudes match Milky Way Cepheids
at the same periods. At greater stellar densities we find that the
empirically measured amplitudes match the values predicted (with no
free parameters) from crowding assessed in the conventional way from
local regions, confirming their accuracy for estimating the background
at the Cepheid locations. Extragalactic Cepheid amplitudes would need
to be ∼20% smaller than measured to indicate additional, unrecognized
crowding as a primary source of the present discrepancy in H0. Rather,
we find the amplitude data constrains a systematic mis-estimate of
Cepheid backgrounds to be 0.029R±0.037mag, more than 5x smaller than
the size of the present ∼0.2mag tension in H0. We conclude that
systematic errors in Cepheid backgrounds do not provide a plausible
resolution to the Hubble tension.
Description:
We used multi-epoch NIR imaging with HST/WFC3 to measure light curves
and amplitudes of optically identified Cepheids. Such observations are
available for SN Ia hosts NGC 5643, NGC 1559, and NGC 2525 and for
NGC4258 (HST Programs 15145, 15640, 15693 and 13445), the megamaser
host used for the geometric calibration of Cepheid luminosities.
See Section 4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 27 56 Amplitude data for Milky Way Cepheids
table3.dat 54 224 Amplitude and crowding data for extragalactic Cepheid
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJ/699/539 : Cepheids in SN-Ia host galaxies (Riess+, 2009)
J/ApJS/193/12 : JHK photometry of Northern Galactic Cepheids (Monson+, 2011)
J/ApJ/730/119 : HST/WFC3 observations of Cepheids in SN Ia hosts (Riess+, 2011)
J/ApJ/830/10 : HST obs. of Cepheids in SNIa host gal. (Hoffmann+, 2016)
J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)
J/ApJ/876/85 : HST observations for LMC Cepheids (Riess+, 2019)
J/ApJ/889/5 : HST obs. of Mira variables in NGC1559 (Huang+, 2020)
http://archive.stsci.edu/hst/ : MAST HST archive
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Cepheid name (1)
11- 15 F5.2 d Per [10.15/69.16] Period
17- 21 F5.3 mag Vamp [0.6/1.34] Amplitude, V band magnitude
23- 27 F5.3 mag Hamp [0.17/0.55] Amplitude, H band magnitude
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Note (1): The sources of light curves are Laney & Stobie (1992A&AS...93...93L 1992A&AS...93...93L),
Monson & Pierce (2011, J/ApJS/193/12), and Riess+ (2018ApJ...861..126R 2018ApJ...861..126R).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID Cepheid Identifier
10- 15 A6 --- host Galaxy host (n1559, n2525, n5643 or "n4258i" or
"n4258o") (1)
17- 22 F6.4 [d] logP [1/2.1] Log Period
24- 29 F6.3 mag dmV [-0.11/0.19] Crowding correction, V band magnitude
31- 35 F5.3 mag dmH [0.016/2.03] Crowding correction, H band magnitude
37- 41 F5.3 mag Vamp [0.26/1.22] Amplitude, V band magnitude
43- 48 F6.3 mag Hamp [-0.21/0.51] Amplitude, H band magnitude
50- 54 F5.3 mag sigma [0.06/0.18] Combined error (2)
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Note (1): Multi-epoch HST/WFC3 observations of hosts in F160W:
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Host Epochs Exp (s) HST programs Number of
Cepheids
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NGC 5643 9 1000 5145, 15640 102
NGC 1559 9 1000 5145 78
NGC 2525 13 900-1100 15145, 15693 15
NGC 4258i 12 2200 3445 27
NGC 4258o 4 1500 5640 2
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Note: Number of Cepheids with well-fit NIR light curves, σamp<0.15.
Note (2): Combined error, σi for eq 14-17 including dispersion in the MW
relation, 0.05 intrinsic scatter, and propagated uncertainty in dmH.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Nov-2021