The Size and Shape of the Milky Way Disk and Halo from M-type Brown Dwarfs in the BoRG Survey

Vledder, I. van; Vlugt, D. van der; Holwerda, Benne W.; Kenworthy, Matthew A.; Bouwens, R. J.; Trenti, Michele

doi:10.1093/mnras/stw258

Cited by 15 publications

(15 citation statements)

References 27 publications

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“…component well above the plane of the disk, i.e., we are including the density of Halo stars in our disk fit. A 0.1 dex offset suggest of order 10% of the stars in are, in fact, Halo stars (see also van Vledder et al 2016). The values in Figure 27 and Table 10 are still too high to be consistent with previous work on the vertical scale of stars in the thin disk.…”

Section: Future Worksupporting

confidence: 74%

MILKY WAY RED DWARFS IN THE BoRG SURVEY; GALACTIC SCALE-HEIGHT AND THE DISTRIBUTION OF DWARF STARS IN WFC3 IMAGING

Holwerda

Trenti

Clarkson

et al. 2014

ApJ

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We present a tally of Milky Way late-type dwarf stars in 68 Wide Field Camera 3 (WFC3) pure-parallel fields (227 arcmin 2) from the Brightest of Reionizing Galaxies survey for high-redshift galaxies. Using spectroscopically identified M-dwarfs in two public surveys, the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey and the Early Release Science mosaics, we identify a morphological selection criterion using the half-light radius (r 50), a near-infrared J − H, G − J color region where M-dwarfs are found, and a V − J relation with M-dwarf subtype. We apply this morphological selection of stellar objects, color-color selection of M-dwarfs, and optical-near-infrared color subtyping to compile a catalog of 274 M-dwarfs belonging to the disk of the Milky Way with a limiting magnitude of m F 125W < 24(AB). Based on the M-dwarf statistics, we conclude that (1) the previously identified north-south discrepancy in M-dwarf numbers persists in our sample; there are more M-dwarfs in the northern fields on average than in southern ones, (2) the Milky Way's single disk scale-height for M-dwarfs is 0.3-4 kpc, depending on subtype, (3) the scale-height depends on M-dwarf subtype with early types (M0-4) high scale-height (z 0 = 3-4 kpc) and later types M5 and above in the thin disk (z 0 = 0.3-0.5 kpc), (4) a second component is visible in the vertical distribution, with a different, much higher scale-height in the southern fields compared to the northern ones. We report the M-dwarf component of the Sagittarius stream in one of our fields with 11 confirmed M-dwarfs, seven of which are at the stream's distance. In addition to the M-dwarf catalog, we report the discovery of 1 T-dwarfs and 30 L-dwarfs from their near-infrared colors. The dwarf scale-height and the relative low incidence in our fields of Land T-dwarfs in these fields makes it unlikely that these stars will be interlopers in great numbers in color-selected samples of high-redshift galaxies. The relative ubiquity of M-dwarfs however will make them ideal tracers of Galactic halo substructure with EUCLID and reference stars for James Webb Space Telescope observations.

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Section: Future Worksupporting

confidence: 74%

MILKY WAY RED DWARFS IN THE BoRG SURVEY; GALACTIC SCALE-HEIGHT AND THE DISTRIBUTION OF DWARF STARS IN WFC3 IMAGING

Holwerda

Trenti

Clarkson

et al. 2014

ApJ

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“…While both haloes are richly substructured and qualitatively agree with the ΛCDM paradigm of galaxy formation, they display significant differences. The Milky Way halo has a weak to no metallicity gradient (Sesar et al 2011;Xue et al 2015) and its stellar density distribution can be described by a broken power-law -within 25 − 30 kpc, it follows an oblate, ρ ∝ r −γ powerlaw distribution with index γ ∼ 2.5 − 3 (Yanny et al 2000;Bell et al 2008;Jurić et al 2008;van Vledder et al 2016) whereas a more rapidly declining stellar density is detected beyond ∼ 30 kpc, with γ ∼ 3.5 (Deason et al 2011;Sesar et al 2011;Deason et al 2014;Cohen et al 2015;Slater et al 2016). M31, on the other hand, has a clear metallicity gradient with a 1 dex variation in [Fe/H] from 10 to ∼100 kpc (Gilbert et al 2014;Ibata et al 2014) and its stellar density distribution can be described by a single power-law with γ ∼ 3.3 (Guhathakurta et al 2005;Gilbert et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Diverse stellar haloes in nearby Milky Way mass disc galaxies

Harmsen

Monachesi

Bell

et al. 2016

Mon. Not. R. Astron. Soc.

127

227

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We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly-inclined Milky Way-mass disc galaxies using HST data from the GHOSTS survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of between −2 and −3.7 and a diversity of stellar halo masses of 1 − 6 × 10 9 M , or 2 − 14% of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power law fit is 0.05 − 0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at ∼ 25 kpc between 0.4 − 0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the Milky Way and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients and density profiles.

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“…Similarly, a search for the lowest-mass substellar objects belonging to the Milky Way can benefit from observations such as the above default parallels. The randomized sampling of the Milky Way volume equally benefits constraints on the shape of the Milky Way (Pirzkal et al 2005(Pirzkal et al , 2009Ryan et al 2005Ryan et al , 2011Ryan et al , 2017Holwerda et al 2014Holwerda et al , 2018van Vledder et al 2016). The near-infrared observations of JWST are sensitive to Figure 1.…”

Section: Science Case B: Brown Dwarf Population Of the Milky Waymentioning

confidence: 99%

“…The WFC3 Infrared Spectroscopic Parallel Survey (WISP) default parallel grism survey with HST/WFC3 (Atek et al 2010) has successfully characterized the intermediate-redshift population (e.g., Atek et al 2011Atek et al , 2014Bedregal et al 2013;Malkan & WISP Team 2013), predicted more use of grism spectroscopy in NIR surveys (Colbert et al 2013), and identified some Milky Way halo objects (Masters et al 2012). Grism observations also hold the potential to cleanly separate AGN and star formation contributions in intermediate-redshift galaxy populations (Trump et al 2011;Bridge et al 2016).…”

Section: Science Case F: Grism Observationsmentioning

confidence: 99%

Default Parallels: The Science Potential of JWST Parallel Observations during TSO Primary Observations

Holwerda

Fraine

Mouawad

et al. 2019

PASP

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The James Webb Space Telescope (JWST) will observe several stars for long cumulative durations while pursuing exoplanets as primary science targets for both Guaranteed Time Observations (GTO) and very likely General Observer (GO) programs. Here we argue in favor of an automatic default parallel program to observe, e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order to find high redshift (z?10) galaxies, cool red/brown dwarf substellar objects, solar system objects, and observations of serendipitous planetary transits. We argue here the need for automated exploratory astrophysical observations with unused JWST instruments during these long-duration exoplanet observations. Randomized fields that are observed in parallel mode reduce errors due to cosmic variance more effectively than single continuous fields of a typical wedding cake observing strategy. Hence, we argue that the proposed automated survey will explore a unique and rich discovery space in the highredshift universe, Galactic structure, and solar system. We show that the GTO and highly probable GO target list of exoplanets covers the Galactic disk/halo and high redshift universe, mostly well out of the plane of the disk of the Milky Way. Exposure times are of the order of the CEERS GTO medium-deep survey in a single filter, comparable to CANDELS in Hubble Space Telescopeʼs surveys and deep fields. The area covered by NIRISS and NIRCam combined could accumulate to a half square degree surveyed.

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The Size and Shape of the Milky Way Disk and Halo from M-type Brown Dwarfs in the BoRG Survey

Cited by 15 publications

References 27 publications

MILKY WAY RED DWARFS IN THE BoRG SURVEY; GALACTIC SCALE-HEIGHT AND THE DISTRIBUTION OF DWARF STARS IN WFC3 IMAGING

MILKY WAY RED DWARFS IN THE BoRG SURVEY; GALACTIC SCALE-HEIGHT AND THE DISTRIBUTION OF DWARF STARS IN WFC3 IMAGING

Diverse stellar haloes in nearby Milky Way mass disc galaxies

Default Parallels: The Science Potential of JWST Parallel Observations during TSO Primary Observations

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