The Dragonfly Nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos Around Spiral Galaxies

Merritt, Allison; Dokkum, Pieter van; Abraham, Roberto; Zhang, Jielai

doi:10.3847/0004-637x/830/2/62

Cited by 149 publications

(319 citation statements)

References 91 publications

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“…To better compare our results to deep surface photometry of M101ʼs integrated stellar light (M+13, van Dokkum et al 2014;Merritt et al 2016), we can also calculate the expected surface brightness of the WFC3 field, given the observed RGB and AGB populations in the CMD. We start with the RGB, by summing the light from all stars detected along the RGB down to a cutoff magnitude of F814W=27.45 (M F814W = −1.75; see Figure 5).…”

Section: Wfc3 Field: Surface Brightnessmentioning

confidence: 99%

“…While the distribution and kinematics of the extended HI disk can be probed relatively simply via 21 cm line emission mapping, the surface brightness of the outer stellar component (μ V 26 mag arcsec −2 ) is well below that of the night sky, requiring very deep and accurate surface photometry to measure its structure and optical colors (e.g., Bakos et al 2008;Erwin et al 2008;Watkins et al 2014Watkins et al , 2016Zheng et al 2015;Merritt et al 2016;Peters et al 2017). A complementary approach is available for nearby galaxies (10 Mpc): the study of the discrete stellar populations via deep Hubble Space Telescope (HST) imaging of individual stars in a galaxy's disk.…”

Section: Introductionmentioning

confidence: 99%

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Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

Mihos

Durrell

Feldmeier

et al. 2018

ApJ

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We use deep Hubble Space Telescope imaging in the outskirts of the nearby spiral M101 to study stellar populations in the galaxy's outer disk and halo. Our Advanced Camera for Surveys (ACS) field lies 17 6 (36 kpc) from the center of M101 and targets the blue "NE Plume" of M101ʼs outer disk, while the parallel Wide Field Camera 3 (WFC3) field lies at a distance of 23 3 (47 kpc) to sample the galaxy's stellar halo. The WFC3 halo field shows a well-defined red giant branch characterized by low metallicity ([M/H] =−1.7±0.2), with no evidence of young stellar populations. In contrast, the ACS disk field shows multiple stellar populations, including a young main sequence, blue and red helium-burning stars, and old RGB and asymptotic giant branch (AGB) populations. The mean metallicity of these disk stars is quite low: [M/H]=−1.3±0.2 for the RGB population, and −1.15±0.2 for the younger helium-burning sequences. Of particular interest is a bunching of stars along the BHeB sequence, indicative of an evolving cohort of massive young stars. We show that the young stellar populations in this field are well-described by a decaying burst of star formation that peaked ∼300-400 Myr ago, along with a more extended star formation history to produce the older RGB and AGB populations. These results confirm and extend the results from our previous deep surface photometry of M101ʼs outer disk, providing an important cross-check on stellar population studies using resolved stellar populations versus integrated light photometry. We discuss our results in the context of halo formation models and the interaction history of M101 and its companions.

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Section: Wfc3 Field: Surface Brightnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

Mihos

Durrell

Feldmeier

et al. 2018

ApJ

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“…Recent success in the determination of both stellar halo density profiles (e.g., Merritt et al 2016;Harmsen et al 2016) and satellite populations (Crnojević et al 2016;Toloba et al 2016) of nearby galaxies will soon enable similar studies on a sample of external galaxies.…”

Section: The Mw's Likely Poor and Concentrated Ashmentioning

confidence: 99%

The accreted stellar halo as a window on halo assembly in L* galaxies

Amorisco

2017

Monthly Notices of the Royal Astronomical Society: Letters

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Theory and observations agree that the accreted stellar halos (ASHs) of Milky Way-like galaxies display significant scatter. I take advantage of this stochasticity to invert the link between halo assembly history (HAH) and ASH, using mock ASHs corresponding to 750 ΛCDM HAHs, sharing a final virial mass of M h (z = 0) = 10 12.25 M . Hosts with poor/rich ASHs assemble following orthogonal growth-patterns. Hosts with rich ASHs experience accretion events (AEs) with high virial mass ratios (HVMRs, M s /M h 0.1) at 0.5 z inf all 1.5, in a phase of fast growth. This maximizes the accreted stellar mass under the condition these satellites are disrupted by z = 0. At similar times, hosts with poor ASHs grow slowly through minor mergers, with only very recent HVMR AEs: this results in a globally more abundant satellite population and in distinctive surviving massive satellites (stellar mass log M s, * /M 9). Several properties of the Milky Way are in agreement with the predictions of this framework for hosts with poor, concentrated ASHs, including: i) the recent infall of Sagittarius and Magellanic Clouds, ii) the likely higher-than-average concentration of its dark halo, iii) the signatures of fast chemical enrichment of a sizable fraction of its halo stellar populations.

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“…These objects drew our attention to the galaxy in the first place: it is a large, low surface-brightness blob in our Dragonfly Telephoto Array imaging (Abraham & van Dokkum 2014;Merritt et al 2016), but a collection of point-like sources in the Sloan Digital Sky Survey.…”

Section: Introductionmentioning

confidence: 99%

An Enigmatic Population of Luminous Globular Clusters in a Galaxy Lacking Dark Matter

Dokkum¹,

Cohen²,

Danieli³

et al. 2018

ApJL

Self Cite

100

155

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We recently found an ultra diffuse galaxy (UDG) with a half-light radius of R e =2.2 kpc and little or no dark matter. The total mass of NGC1052-DF2 was measured from the radial velocities of bright compact objects that are associated with the galaxy. Here, we analyze these objects using a combination of Hubble Space Telescope (HST) imaging and Keck spectroscopy. Their average size is r 6.2 0.5 h á ñ =  pc and their average ellipticity is 0.18 0.02From a stacked Keck spectrum we derive an age of 9 Gyr and a metallicity of [Fe/H]=−1.35±0.12. Their properties are similar to ω Centauri, the brightest and largest globular cluster in the Milky Way, and our results demonstrate that the luminosity function of metal-poor globular clusters is not universal. The fraction of the total stellar mass that is in the globular cluster system is similar to that in other UDGs, and consistent with "failed galaxy" scenarios, where star formation terminated shortly after the clusters were formed. However, the galaxy is a factor of ∼1000 removed from the relation between globular cluster mass and total galaxy mass that has been found for other galaxies, including other UDGs. We infer that a dark matter halo is not a prerequisite for the formation of metal-poor globular cluster-like objects in high-redshift galaxies.

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The Dragonfly Nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos Around Spiral Galaxies

Cited by 149 publications

References 91 publications

Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101

The accreted stellar halo as a window on halo assembly in L* galaxies

An Enigmatic Population of Luminous Globular Clusters in a Galaxy Lacking Dark Matter

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