Anchors for the cosmic distance scale: the Cepheids U Sagittarii, CF Cassiopeiae, and CEab Cassiopeiae

Majaess, D.; Carraro, G.; Bidin, C. Moni; Bonatto, Charles Jose; Бердников, Л. Н.; Balam, D. D.; Moyano, Maximiliano; Gallo, L. C.; Turner, D. G.; Lane, David J.; Gieren, W.; Borissova, J.; Kovtyukh, V. V.; Beletsky, Y.

doi:10.1051/0004-6361/201322670

Cited by 24 publications

(24 citation statements)

References 90 publications

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“…The temperature, gravity, and rotational velocity of boxC stars were measured by fitting the H α and H β Balmer lines and the 4922Å He I feature with synthetic spectra, as was done in Majaess et al (2013) for similar MS stars. With this aim, we employed the fitprof21 code, developed by Bergeron et al (1992) and Saffer et al (1994) and subsequently modified by Napiwotzki et al (1999).…”

Section: Boxesc and D: Stellar Parametersmentioning

confidence: 99%

Galactic Structure in the Outer Disk: The Field in the Line of Sight to the Intermediate-Age open Cluster Tombaugh 1*

Carraro

Silva

Bidin

et al. 2017

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We employ optical photometry and high-resolution spectroscopy to study a field toward the open cluster Tombaugh1, where we identify a complex population mixture that we describe in terms of young and old Galactic thin disks. Of particular interest is the spatial distribution of the young population, which consists of dwarfs with spectral types as early as B6 and is distributed in a blue plume feature in the color-magnitude diagram. For the first time, we confirm spectroscopically that most of these stars are early-type stars and not blue stragglers or halo/ thick-disk subdwarfs. Moreover, they are not evenly distributed along the line of sight but crowd at heliocentric distances between 6.6 and 8.2 kpc. We compare these results with present-day understanding of the spiral structure of the Galaxy and suggest that they trace the outer arm. This range of distances challenges current Galactic models adopting a disk cutoff at 14 kpc from the Galactic center. The young dwarfs overlap in space with an older component, which is identified as an old Galactic thin disk. Both young and old populations are confined in space since the disk is warped at the latitude and longitude of Tombaugh1. The main effects of the warp are that the line of sight intersects the disk and entirely crosses it at the outer arm distance and that there are no traces of the closer Perseus arm, which would then be either unimportant in this sector or located much closer to the formal Galactic plane. Finally, we analyze a group of giant stars, which turn out to be located at very different distances and to possess very different chemical properties, with no obvious relation to the other populations.

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Section: Boxesc and D: Stellar Parametersmentioning

confidence: 99%

Galactic Structure in the Outer Disk: The Field in the Line of Sight to the Intermediate-Age open Cluster Tombaugh 1*

Carraro

Silva

Bidin

et al. 2017

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“…Distances are evaluated for Cepheids in IC 1613 and NGC 6822 using an updated Galactic calibration tied to cluster Cepheids (e.g., Turner 2010; Majaess et al 2013c), and nearby Cepheids exhibiting HST parallaxes (Benedict et al 2007). The distances are computed using a reddening-free (VI c ) Wesenheit function and nonlinear mid-infrared relations (Neilson et al 2009;Majaess et al 2013a), whereby the latter rely partly on new multi-epoch Spitzer photometry for Galactic Cepheids (Monson et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The population II Cepheids were omitted (Udalski et al 2001;Majaess et al 2009). Cepheid distances were evaluated using the Galactic W VI c relation compiled by Majaess et al (2013c), which is anchored to the HST parallaxes of Benedict et al (2007) and an updated version of the Turner (2010) cluster Cepheid list (W VI c,0 = −3.31 log P 0 − 2.56). For example, new parameters were adopted for the cluster Cepheids SU Cas, V340 Nor, QZ Nor, CF Cas, TW Nor, etc.…”

Section: Introductionmentioning

confidence: 99%

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Evidence for photometric contamination in key observations of Cepheids in the benchmark galaxy IC 1613

Majaess

Turner

Gieren

et al. 2014

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This study helps increase awareness of the pernicious effects of photometric contamination (crowding/blending), since it can propagate an undesirable systematic offset into the cosmic distance scale. The latest Galactic Cepheid Wesenheit (VI c ) and Spitzer calibrations were employed to establish distances for classical Cepheids in IC 1613 and NGC 6822, thus enabling the impact of photometric contamination to be assessed in concert with metallicity. Distances (W VIc , [3.6]) for Cepheids in IC 1613 exhibit a galactocentric dependence, whereby Cepheids near the core appear (spuriously) too bright (r g < 2 ). That effect is attributed to photometric contamination from neighboring (unresolved) stars, since the stellar density and surface brightness may increase with decreasing galactocentric distance. The impact is relatively indiscernible for a comparison sample of Cepheids occupying NGC 6822, a result that is partly attributable to that sample being nearer than the metal-poor galaxy IC 1613. W VIc and [3.6] distances for relatively uncontaminated Cepheids in each galaxy are comparable, thus confirming that period-magnitude relations (Leavitt Law) in those bands are relatively insensitive to metallicity (Δ[Fe/H] 1).

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“…So, we also spectroscopically analyzed XZ CMa to confirm or exclude the cluster membership. In fact, cluster Cepheids are important to fixing the distance scale (see, e.g., Majaess et al 2013aMajaess et al , 2013b.…”

Section: Tombaugh1: Backgroundmentioning

confidence: 99%

PROPERTIES OF THE OPEN CLUSTER TOMBAUGH 1 FROM HIGH-RESOLUTION SPECTROSCOPY AND uvbyCaHβ PHOTOMETRY*

Silva

Carraro²,

Anthony-Twarog

et al. 2015

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Open clusters can be the key to deepening our knowledge on various issues involving the structure and evolution of the Galactic disk and details of stellar evolution because a cluster's properties are applicable to all its members. However, the number of open clusters with detailed analysis from high-resolution spectroscopy or precision photometry imposes severe limitations on studies of these objects. To expand the number of open clusters with well-defined chemical abundances and fundamental parameters, we investigate the poorly studied, anticenter open cluster Tombaugh 1. Using precision uvbyCaHβ photometry and high-resolution spectroscopy, we derive the cluster's reddening, obtain photometric metallicity estimates, and, for the first time, present a detailed abundance analysis of 10 potential cluster stars (nine clump stars and one Cepheid). Using the radial position from the cluster center and multiple color indices, we have isolated a sample of unevolved, probable single-star members of Tombaugh 1. From 51 stars, the cluster reddening is found to be -.008, where the errors refer to the internal standard errors of the mean. The weighted photometric metallicity from m 1 and hk is [Fe/H]=−0.10±0.02, while a match to the Victoria-Regina Strömgren isochrones leads to an age of 0.95±0.10 Gyr and an apparent modulus of -m M ( )=13.10±0.10. Radial velocities identify six giants as probable cluster members, and the elemental abundances of Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Y, Ba, Ce, and Nd have been derived for both the cluster and the field stars. Tombaugh 1 appears to be a typical inner thin disk, intermediate-age open cluster of slightly subsolar metallicity, located just beyond the solar circle, with solar elemental abundance ratios except for the heavy s-process elements, which are a factor of two above solar. Its metallicity is consistent with a steep metallicity gradient in the galactocentric region between 9.5 and 12 kpc. Our study also shows that Cepheid XZ CMa is not a member of Tombaugh 1 and reveals that this Cepheid presents signs of barium enrichment, making it a probable binary star.

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Anchors for the cosmic distance scale: the Cepheids U Sagittarii, CF Cassiopeiae, and CEab Cassiopeiae

Cited by 24 publications

References 90 publications

Galactic Structure in the Outer Disk: The Field in the Line of Sight to the Intermediate-Age open Cluster Tombaugh 1*

Galactic Structure in the Outer Disk: The Field in the Line of Sight to the Intermediate-Age open Cluster Tombaugh 1*

Evidence for photometric contamination in key observations of Cepheids in the benchmark galaxy IC 1613

PROPERTIES OF THE OPEN CLUSTER TOMBAUGH 1 FROM HIGH-RESOLUTION SPECTROSCOPY AND uvbyCaHβ PHOTOMETRY*

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