Sloshing in its cD halo: MUSE kinematics of the central NGC 3311 in the Hydra I cluster

C. E. Barbosa1, M. Arnaboldi2, L. Coccato2, O. Gerhard3, C. Mendes de Oliveira1, M. Hilker2, T. Richtler4

1Universidade de S˜aoPaulo, S˜aoPaulo, Brazil 2European Southern Observatory, Garching, Germany 3Max-Planck-Institut fur Extraterrestrische Physik, Garching, Germany 4Universidad Concepci´on,Concepci´on,Chile

USP-IAG Extragalactic Seminar September 20th, 2017

Credit: Gemini Observatory Introduction: Galaxy clusters and BCGs

Galaxy cluster Abell 370. Credit: HST / NASA Introduction: Galaxy clusters and BCGs

BCG =

Galaxy cluster Abell 370. Credit: HST / NASA Introduction: cD

I Type-cD galaxies (cD galaxies) is a subtype of giant elliptical galaxies (D) in the Bautz-Morgan classification. Quoting Morgan and Lesh (1965) (a) they are located in clusters, of which they are outstandingly the brightest and largest members; (b) they are centrally located in their clusters; (c) they are never highly flattened in shape; (d) they are of a characteristic appearance, having bright, elliptical-like [centers], surrounded by an extended amorphous envelope. cD envelopes

I SB profiles of cD galaxies deviate from the R1/4 law (de Vaucouleurs 1953)

I Envelopes have shallow surface brightness profiles

: NGC 3311 at the Hydra I cluster Figure from Sarazin (1986). Formation of cD galaxies

I Massive, passive evolving galaxies are identified at z ∼ 2.5 (Cimatti et al. 2004).

I ”Red nuggets” population are believed to be precursor of the nearby early-type galaxies (van Dokkum et al. 2009; Cassata et al. 2010)

I Among different models, the two-phase formation scenario (Oser et al. 2010) is among the most promising to explain the formation of galaxies. I Central region is formed in a fast dissipative process early (z & 3) I Stellar halo is accreted at later epochs stochastically I This model is able to explain the growth of massive galaxies since z = 2 (van Dokkum et al. 2010) . Formation of cD galaxies

I To test the two-phase scenario, it is necessary to identify the different signatures left by dissipative processes ( formed in situ) and accretion events (stars formed ex situ).

I Two dimensional (2D) studies have been able to identify this signatures I Gonzalez et al. (2005) and Huang et al. (2013) have been able to probe the existence of different structural components in ETGs.

I The identification of the kinematic signatures of the outer stellar halo components at large distances is hampered primarily by the low S/N. Simulations results

I 0-2: different projections of galaxy indicate triaxiality

I 3: accreted BCG stars

I 4: in situ BCG stars

I 5: stars associated to surviving progenitors: coherent strams, linear overdensities

I 6: stars associated to sub-resolution halos

I 7: changing resolution to match other simulations

Simulations from Cooper et al. (2015) I 8: changing in the parameter of particle-tagging method. I Rising, asymmetric velocity dispersion profile (Loubser et al. 2008; Richtler et al. 2011). I Unmixed populations of PNe (Ventimiglia et al. 2011).

The case of NGC 3311

I Central galaxy of the cluster Abell 1060 (Hydra cluster) I D ≈ 50 Mpc.

NGC 3309 NGC 3311 I Unmixed populations of PNe (Ventimiglia et al. 2011).

The case of NGC 3311

I Central galaxy of the cluster Abell 1060 (Hydra cluster) I D ≈ 50 Mpc. I Rising, asymmetric velocity dispersion profile (Loubser et al. 2008; Richtler et al. 2011).

NGC 3309 NGC 3311 Loubser et al. 2008 The case of NGC 3311

I Central galaxy of the cluster Abell 1060 (Hydra cluster) I D ≈ 50 Mpc. I Rising, asymmetric velocity dispersion profile (Loubser et al. 2008; Richtler et al. 2011). I Unmixed populations of PNe (Ventimiglia et al. 2011).

NGC 3309 NGC 3311 Loubser et al. 2008

Ventimiglia et al. 2011 I (B) V-band residuals from maximum symmetric model of Arnabold et al. 2012;

I (C) X-rays from Hayakawa et al. 2004.

Existence of large asymmetric feature

I (A) V-band image + dwarf galaxies from Misgeld et al. 2008; I (C) X-rays from Hayakawa et al. 2004.

Existence of large asymmetric feature

I (A) V-band image + dwarf galaxies from Misgeld et al. 2008;

I (B) V-band residuals from maximum symmetric model of Arnabold et al. 2012; Existence of large asymmetric feature

I (A) V-band image + dwarf galaxies from Misgeld et al. 2008;

I (B) V-band residuals from maximum symmetric model of Arnabold et al. 2012;

I (C) X-rays from Hayakawa et al. 2004. Previous work

I FORS2 observations at VLT in MXU masking mode.

I Onion-like pattern produced with 6 masks.

I Long-slits from previous works (Richtler et al. 2011; Coccato et al. 2011) Stellar population properties support two-phase scenario

Stellar populations in cD galaxy NGC 3311 (Barbosa et al. 2016) Complex dynamical properties

Kinematics of NGC 3311 (Hilker, Barbosa et al. 2017, in prep.) New observations of NGC 3311 with MUSE@VLT

Observations carried out at 8m telescope UT4

at the VLT, Paranal (Chile).

MUSE integral field spectrograph.

I New observations with MUSE I Wide Field Mode (1 arcmin2), 0.2 arcsec / pixel I 4650 & λ(A˚) & 9300 I Data reduced with ESO Reflex pipeline.

UT1 telescope at Paranal. Strategy

I Separation of dwarf galaxies and I Observation of four fields UCDs from the halo with SExtractor (Bertin and Arnouts fields A-C observe central I 1996) galaxy + offset halo I field D allocated in the tidal I Voronoi binning (Cappellari and tail of HCC 007 Copin 2003) to achieve S/N≈ 70 / bin. Methods

I Calculation of LOS Velocity distribution (LOSVD) with pPXF (Cappellari and Emsellem 2004).

I Fitting of Gaussian-Hermite profile with four moments: V , σ, h3, h4 I Use of two components: SSPs + emission lines

I Emission lines re-analyzed individually after subtraction of stellar continuum to improve accuracy Sanity check: comparison with other observations

I Comparison with long-slit observations from Richtler et al. (2011)

I Also included onion-shell-like observations from Hilker et al. (2017 submitted).

Comparison with long-slit observations. Systemic velocity

−1 I Velocity offset of ∼50 km s between the systemic velocity of the central region and the outer halo

I The central galaxy has a 2D velocity field that does not satisfy point-symmetry.

I Analysis of velocity field with kinemetry (Krajnovi´cet al. 2006) indicates that the system is not supported by rotation

I May be classified as slow rotator (SR) according to ATLAS3D criteria Velocity dispersion

I Velocity dispersion increases with the radius, from ∼180 km s−1 to ∼300 km s−1 in the outermost data points.

I Stars in the halo are bound to the cluster’s gravitational potential. I σ does not reach the velocity dispersion of the cluster of 647 km s−1 (Struble and Rood 1999). Skewness (γ3) and kurtosis (γ4)

γ3 I h3 ≈ √ h ≈ γ4√−3 4 3 I 4 8 6 I Measures the asymmetry of the I Probe radial (h4 > 0) and LOSVD tangencial (h4 < 0) anisotropies. Photometry

(A) V-band FORS2/VLT imaging from Arnaboldi et al. (2012) (B) galfitm (Vika et al. 2013) modelling of three main galaxies (C) Using non-photometric component to produce mostly positive residuals Photometry

Surface brightness profile at 55 degrees. I NGC 3311 is modeled with 4 S´ersiccomponents I A-C are almost concentrical I Residuals indicate substructures I D component is offset by 8 kpc Modeling the kinematics

I Multiple non-rotating components in the LOS

I LOSVD is given by superposition weighted by the luminosity

I Finite mixture modeling of N components, i = 1, .., N, with individual LOSVD Li(v), the expected value is given by

Z +∞ Ei[g(v)] = g(v)Li(v)dv −∞

I Considering an arbitrary function g(v)

I for the mean, g(v) = µi = v 2 2 I for the velocity dispersion, g(v) = σi = (v − µ)

I In a finite mixture model PN I E[g(v)] = i=1 wiEi[g(v)] m PN Pm m m−j j I E[(v − µ) ] = i=1 j=0 j wi(µi − µ) E[(v − µi) ]

I Weights (wi) in the model are given by the photometric components Modeling the kinematics: toy model

I MUSE field with three Sersic components

I Each of these components have its own V , σ, h3 and h4 which are constant.

I All the spatial variation is in the kinematics is set by the variation of the luminosity of the sources. Modeling the kinematics: toy model Results of kinematic modeling Results of kinematic modeling

I Parameters for the kinematics of each component in the finite mixture model.

Component V (km / s) σ (km / s) h3 h4 A+B 3856.7 ± 1.5 152.8 ± 2.6 −0.056 ± 0.008 −0.076 ± 0.019 C 3836 ± 6 188 ± 7 0.000 ± 0.020 −0.010 ± 0.027 D 3978 ± 13 327 ± 9 −0.097 ± 0.011 0.036 ± 0.012 Results of kinematic modeling

I Good description of variations of all moments

I Does not require large anisotropies

I Direct inference of velocity offset between galaxy and cD halo ∆V ∼ 120km s−1. Scaling relations

Preliminary conclusions:

I Each modeled component follow the values predicted from scaling relations

I Components are close to virialization. Final results

I FMD modeling: galaxy + cD halo have a relative velocity of 173 km s−1 in relation to the cluster velocity (V =3683 km s−1): 20% of the velocity dispersion

I Our results + X-ray indicates a non-related halo.

I Cause of this motion: on-going sub-cluster merging. ReferencesI

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