Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients

Urich, Linda; Lisker, Thorsten; Janz, Joachim; Ven, Glenn van de; Leaman, Ryan; Boselli, A.; Paudel, Sanjaya; Sybilska, Agnieszka; Peletier, Reynier F.; Brok, Mark den; Hensler, G.; Toloba, Elisa; Falcón-Barroso, J.; Niemi, Sami-Matias

doi:10.1051/0004-6361/201730897

Cited by 30 publications

(26 citation statements)

References 91 publications

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“…As an observable signature that should be studied those cluster dEs should show a negative vertical stellar age gradient and a positive blue colour gradient or at least flat ones, as well as a radially increasing stellar velocity dispersion. This effect might already be indicated by a few dEs in the Coma cluster with radial changes in age (Koleva et al 2011) and by the negative or flat age gradients derived in a few Virgo cluster dEs (Urich et al 2017) from the SMAKCED sample (Janz et al 2012).…”

Section: Dwarf Galaxy Transformation and Stellar Population Gradientsmentioning

confidence: 85%

The effect of ram-pressure stripping on dwarf galaxies

Steyrleithner

Hensler

Boselli

2020

Monthly Notices of the Royal Astronomical Society

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Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intra-cluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star-formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disk and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.

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Section: Dwarf Galaxy Transformation and Stellar Population Gradientsmentioning

confidence: 85%

The effect of ram-pressure stripping on dwarf galaxies

Steyrleithner

Hensler

Boselli

2020

Monthly Notices of the Royal Astronomical Society

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“…These latter authors suggested that galaxy harassment is less effective in clusters like Virgo, given their large velocity dispersion, and more efficient in group environments (Yozin & Bekki 2015). Urich et al (2017) claimed that the ram pressure stripping is therefore more likely to explain their blue-core dEs in the Virgo cluster. According to the model of Vollmer (2009), ram pressure stripping has a hard time in removing the gas from the center of the galaxies and it can even raise the star formation rate in the cores (Kronberger et al 2008).…”

Section: Comparison Between the Clusters And Possible Formation Scenamentioning

confidence: 99%

Young stellar populations in early-type dwarf galaxies

Hamraz

Peletier

Khosroshahi

et al. 2019

A&A

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Aims. To understand the stellar population content of early-type dwarf galaxies (dEs) and their environmental dependence, we compare the slopes and intrinsic scatter of color–magnitude relations (CMRs) for three nearby clusters, Fornax, Virgo, and Coma. Additionally, we present and compare internal color profiles of these galaxies to identify central blue regions with younger stars. Methods. We use the imaging of the HST/ACS Fornax cluster in the magnitude range of −18.7 ≤ Mg′ ≤ −16.0 to derive magnitudes, colors, and color profiles, which we compare with literature measurements from the HST/ACS Virgo and Coma Cluster Survey. We take advantage of HST accuracy to investigate and parameterize the (g′−z′) color profiles of these dEs. Results. Based on analysis of the color profiles, we report on a large number of dEs with young stellar populations at their center in all three clusters. While for Virgo and Coma the number of blue-cored dEs is found to be 85%±2% and 53%±3%, respectively, for Fornax, we find that all galaxies have a blue core. We show that bluer cores reside in fainter dEs, similar to the trend seen in nucleated dEs. We find no correlation between the luminosity of the galaxy and the size of its blue core. Moreover, a comparison of the CMRs of the three clusters shows that the scatter in the CMR of Virgo is considerably larger than in the Fornax and Coma clusters. Presenting adaptive smoothing we show that the galaxies on the blue side of the CMR often show evidence for dust extinction, which strengthens the interpretation that the bluer colors are due to young stellar populations. We also find that outliers on the red side of the CMR are more compact than what is expected for their luminosity. We find several of these red outliers in Virgo, often close to more massive galaxies. No red outlying compact early-types are found in Fornax and Coma in this magnitude range while we find three in the Virgo cluster. We show that the CMR of the Fornax and Virgo clusters are slightly bluer than that of Coma. We suggest that the large number of outliers and larger scatter found for Virgo CMR are a result of the alternative assembly history of this cluster.

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“…Given the known stellar population diversity of Virgo cluster early-type dwarfs (Michielsen et al 2008;Kim et al 2010), we examine whether there are systematic differences between the phase-space regions. The recent optical -near-infrared photometric study of Urich et al (2017) provides us with colors and color gradients for 119 Virgo early-type dwarfs. Urich et al defined an age-sensitive and a metallicity-sensitive color by combining g, r, i, and H bands into linear combinations that lead to a nearly orthogonal age-metallicity grid for simple stellar populations.…”

Section: Observational Findingsmentioning

confidence: 99%

The Active Assembly of the Virgo Cluster: Indications for Recent Group Infall From Early-type Dwarf Galaxies

Lisker¹,

Vijayaraghavan²,

Gallagher³

et al. 2018

ApJ

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Virgo is a dynamically young galaxy cluster with substructure in its spatial and kinematic distribution. Here, we simultaneously study the phase-space distribution and the main characteristics of Virgo's galaxies, particularly its most abundant galaxy population -the early-type dwarfs -to understand their environmental transformation histories. Aside from known correlations with morphological types -like the larger average clustercentric distance of late-type galaxies -we find an intriguing behavior of early types with magnitudes −17 ≥ M r ≥ −18. They show a large velocity spread and an asymmetric phase-space distribution, similar to the late-type galaxies and different from the early types just one magnitude brighter/fainter. Furthermore, we find a close phase-space aggregation of early-type dwarfs at large clustercentric distance and high relative velocity. Nearly all of them show signatures of disk components and their colors imply stellar ages that are younger than the population average. They are not located closely together but spread azimuthally around the cluster center. We show that this is expected from simulations of an infalling galaxy group that slowly gets dispersed after its first pericentric passage. We thus conclude that these galaxies are recent arrivals, and that the peculiar phase-space distribution of early-type dwarfs is evidence for the ongoing growth of this galaxy population. Studying galaxies based on their phase space correlations is a unique way to compare the properties of recent and older cluster members, and to understand which environment most influenced their present-day characteristics.

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Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients

Cited by 30 publications

References 91 publications

The effect of ram-pressure stripping on dwarf galaxies

The effect of ram-pressure stripping on dwarf galaxies

Young stellar populations in early-type dwarf galaxies

The Active Assembly of the Virgo Cluster: Indications for Recent Group Infall From Early-type Dwarf Galaxies

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