The central spheroids of Milky Way mass-sized galaxies

Tissera, Patricia B.; Machado, Rubens E. G.; Carollo, D.; Minniti, D.; Zoccali, M.; Meza, Andrés

doi:10.1093/mnras/stx2431

Cited by 28 publications

(26 citation statements)

References 75 publications

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“…For example, Cooper et al (2015) and M2019 choose a spherical region of 5 kpc from the galactic center to mark the frontier between stellar halo and bulge. Other authors choose to avoid this spatial segregation, analyzing the overall "central spheroids" (Tissera et al 2018).…”

Section: Bulge Definitionmentioning

confidence: 99%

The prevalence of pseudo-bulges in the Auriga simulations

Gargiulo

Monachesi

Gómez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We study the galactic bulges in the Auriga simulations, a suite of thirty cosmological magneto-hydrodynamical zoom-in simulations of late-type galaxies in Milky Way-sized dark matter haloes performed with the moving-mesh code AREPO. We aim to characterize bulge formation mechanisms in this large suite of galaxies simulated at high resolution in a fully cosmological context. The bulges of the Auriga galaxies show a large variety in their shapes, sizes and formation histories. According to observational classification criteria, such as Sérsic index and degree of ordered rotation, the majority of the Auriga bulges can be classified as pseudo-bulges, while some of them can be seen as composite bulges with a classical component; however, none can be classified as a classical bulge. Auriga bulges show mostly an in-situ origin, 21% of them with a negligible accreted fraction ( f acc < 0.01). In general, their in-situ component was centrally formed, with ∼ 75% of the bulges forming most of their stars inside the bulge region at z = 0. Part of their in-situ mass growth is rapid and is associated with the effects of mergers, while another part is more secular in origin. In 90% of the Auriga bulges, the accreted bulge component originates from less than four satellites. We investigate the relation between the accreted stellar haloes and the bulges of the Auriga simulations. The total bulge mass shows no correlation with the accreted stellar halo mass, as in observations. However, the accreted mass of bulges tends to correlate with their respective accreted stellar halo mass.

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Section: Bulge Definitionmentioning

confidence: 99%

The prevalence of pseudo-bulges in the Auriga simulations

Gargiulo

Monachesi

Gómez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…We note that the in situ components also contribute with old stars as shown in Tissera et al (2018). Apart from this common feature, each halo has its own peculiarities.…”

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confidence: 69%

“…They also reported that low-metallicity stars are mainly contributed by low-mass satellites, and are more frequent in the outskirts of halos. The central regions of such systems (within ∼10 kpc, including the bulge), where a significant contribution of old stars was found, have been analyzed in detail by Tissera et al (2018).…”

Section: The Simulated Aquarius Galaxiesmentioning

confidence: 99%

“…A negative age profile could arise when low-mass satellites are accreted very early on. These will contribute mostly to the inner regions with their old stars (Tissera et al 2018). Intermediate-and high-mass satellites accreted later on will have younger stellar populations (because they continued forming stars for longer periods) and their stars will populate both the inner and outer regions.…”

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confidence: 99%

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The Origin of the Milky Way's Halo Age Distribution

Carollo

Tissera

Gudin

et al. 2018

ApJL

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We present an analysis of the radial age gradients for the stellar halos of five Milky Way (MW) mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity of age trends, reflecting their different assembly histories. Four of the simulated halos possess clear negative age gradients, ranging from approximately −7 to −19 Myr kpc −1 , shallower than those determined by recent observational studies of the Milky Way's stellar halo. However, when restricting the analysis to the accreted component alone, all of the stellar halos exhibit a steeper negative age gradient with values ranging from −8 to −32 Myr kpc, closer to those observed in the Galaxy. Two of the accretion-dominated simulated halos show a large concentration of old stars in the center, in agreement with the Ancient Chronographic Sphere reported observationally. The stellar halo that best reproduces the current observed characteristics of the age distributions of the Galaxy is that formed principally by the accretion of small satellite galaxies. Our findings suggest that the hierarchical clustering scenario can reproduce the MW's halo age distribution if the stellar halo was assembled from accretion and the disruption of satellite galaxies with dynamical masses less than ∼10 9.5 M ☉ , and a minimal in situ contribution.

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“…The presence of low luminosity objects is also relevant in the context of galaxy formation models, where there is a continuous build up of the spheroidal component by accretion of small proto-galactic fragments (e.g., Helmi & White 1999). In this context, Tissera et al (2017) studied the survival of structures in the inner regions of the MW, finding that some remnants may be detected even within the bulge, and the old GCs may be representative (or tracers) of these fragments, and have been useful in studying the formation and evolution of the Galaxy.…”

Section: Introductionmentioning

confidence: 99%

New VVV Survey Globular Cluster Candidates in the Milky Way Bulge*

Minniti

Geisler

Alonso-García

et al. 2017

ApJL

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It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color-magnitude diagrams. We provide their coordinates as well as their near-IR color-magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color-magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A Ks < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their colormagnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way.

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The central spheroids of Milky Way mass-sized galaxies

Cited by 28 publications

References 75 publications

The prevalence of pseudo-bulges in the Auriga simulations

The prevalence of pseudo-bulges in the Auriga simulations

The Origin of the Milky Way's Halo Age Distribution

New VVV Survey Globular Cluster Candidates in the Milky Way Bulge*

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