Hierarchical Assembly of Stellar Envelopes in Galaxy Clusters Meng - PowerPoint PPT Presentation

Hierarchical Assembly of Stellar Envelopes in Galaxy Clusters Meng Gu (Harvard University) Collaborators: Charlie Conroy, Gabriel Brammer, David Law, Pieter van Dokkum, Renbin Yan, David Wake, Alexa Villaume, Allison Merritt, Roberto Abraham, Jielai Zhang, Paul Harding, Donald Schneider, Kai Zhang, Anne-Marie Weijmans, Dmitry Bizyaev, Niv Drory

Scaling Relations of Early-type Galaxies (ETGs) More massive ETGs Older stellar age More metal rich More alpha-enhanced Thomas et al. 2010 2 /35

Fossil Records in the Stellar Envelopes • Stellar Envelopes of ETGs preserve information about the accretion history • The Illustris simulation • Mean [Z/H] & surface brightness 1Re 4Re profiles do not evolve significantly in the central region • Accretions flatten[Z/H] & surface brightness profiles Cook et al. 2016

BCG assembly in the center of Abell 3827 (z~0.1) image credit: the NASA/ESA Hubble Space Telescope

BCG assembly in the center of Abell 3827 (z~0.1) -59 � 56’30” N13 • VLT/MUSE datacube Abell 3827 z~0.1 • 13 ETGs in the central 70 kpc of -59 � 56’20” 35” the cluster. 40” • Measure stellar populations in the N15 N8 N3 40” N9 N2 central R =1kpc N1 N4 45” N12 • N1-N4 and N9 will merge within N11 1Gyr in to a BCG with 50” 57’00” N7 log(M * /M ⊙ ) ≈ 11.7 N6 N5 55” 10 kpc 20” 330 � 29’30” 00” 28’30” 00” 27’30” 330 � 28’45” 30” 15” 00” Gu et al. 2018b RA (J2000) RA (J2000) arXiv 1805.04520 5 /35

Full-Spectrum Modeling Conroy & van Dokkum 2012 Conroy et al. 2014, 2018 Absorption (Automated) Line Fitter (alf) • Stellar ages > 1Gyr ; Metallicities from ∼ − 2.0 to +0.25 • MIST stellar isochrones, Choi et al. 2016 • MILEs + extended IRTF spectral library, 0.35 to 2.4 µm, Villaume et al. 2017 • Theoretical response functions • MCMC sampler: emcee , MPI parallelized • This work: z, σ , age, [Z/H], abundances of Fe, Mg, fixed to Kroupa IMF example, S/N=100/Å 6 /35

Coordinated Assembly of BCGs in Cluster Center -59 � 56’30” N13 Abell 3827 z~0.1 • The building blocks of Brightest Cluster -59 � 56’20” 35” Galaxies (BCGs) in cluster centers have 40” Dec (J2000) N15 N8 N3 40” N9 N2 N1 N4 45” high [ α /Fe] N12 N11 50” 57’00” N7 N6 N5 55” 10 kpc z~0.1 20” 330 � 29’30” 00” 28’30” 00” 27’30” 330 � 28’45” RA (J2000) 14 0.5 12 10 0.4 Age [Gyr] [Mg/Fe] 8 0.3 6 0.2 4 this work 0.1 Conroy et al. 2014 2 0.0 9 10 11 12 9 10 11 12 log ( M ⇤ / M � ) log ( M ⇤ / M � ) Gu et al. 2018b 10 20 30 40 50 60 70 arXiv 1805.04520 Projected Distance to Cluster Center [kpc]

Coordinated Assembly of BCGs in Cluster Center Scaling Relations Radial Profiles Coordinated [ α /Fe] or log Age [ α /Fe] or log Age Cluster Centers Assembly Random Field Assembly log M ∗ log ( R / R e ) Coordinated Assembly of BCGs: flat & high [ α /Fe] radial profiles high [ α /Fe] building blocks flat & old age radial profiles Gu et al. 2018b arXiv 1805.04520 8 /35

Radial Trends of Stellar Population Properties 26 -59 � 56’30” N13 Abell 3827 Surface Brightness in r -band [mag/arcsec 2 ] 25 -59 � 56’20” 35” 24 23 40” Dec (J2000) N15 N8 22 N3 40” N9 N2 N1 N4 45” 21 N12 20 N11 50” 57’00” 14 kpc N7 19 N6 N5 55” 18 10 kpc 10 kpc 20” 17 330 � 29’30” 00” 28’30” 00” 27’30” 330 � 28’45” 30” 15” 00” RA (J2000) RA (J2000) Gu et al. 2018b arXiv 1805.04520 9 /35

Radial Trends of Stellar Population Properties 14 12 400 Age [Gyr] σ [km/s] 10 300 8 200 6 100 0.5 0.2 0.4 0.0 [Mg/Fe] [Fe/H] 0.3 − 0.2 0.2 − 0.4 0.1 N1 N4 N2 N9 − 0.6 N3 van Dokkum+17 Gu et al. 2018b 0.0 10 − 1 10 0 10 1 10 − 1 10 0 10 1 arXiv 1805.04520 Radius [kpc] Radius [kpc] 10 /35

Beyond 100 kpc

Ancillary Deep Coma Project 6 MaNGA plates Massive Ellipticals from center to ~ 35kpc NGC 4889 • NGC 4874 • NGC 4860 • NGC 4839 • NGC 4841A • 3 Dwarf Ellipticals 3 UDGs (Gu et al. 2018a) 3 bundles on ICL 3 IFU bundles on the sky 1/3 time on nod Exposures image credit: The Dragonfly Telephoto Array

SDSS IV/MaNGA: ICL in the Coma Cluster • Three 127-fiber IFU bundles on the ICL with 13.5 hrs total exposure time • IFU diameter ~32’’ • wavelength coverage: 3622 − 10354Å • spectral resolution: 1560 − 2650 100kpc 150kpc 180kpc Gu et al. 2018c in prep.

Best-Fit Spectrum of ICL1 • ~ 100 kpc from NGC4889 • S/N 4500-5000Å =21/Å • σ ~ 700 km/s • Age ~12.7 Gyr • [Fe/H] ~ -0.7 dex Gu et al. 2018c in prep.

Stars in the ICL Recession velocities are close to two BCGs • Velocity dispersion profiles rise to ~700km/s at 100-200 kpc • Gu et al. 2018c in prep.

Age and Metallicity of Stars in the ICL • [Fe/H]: • Stellar Age: • Declining radial profiles • > 10 Gyr within 20 kpc • [Fe/H] ~ -0.1 in the center • > 5 Gyr within 35 kpc • [Fe/H] ~ -0.4 at 20-35 kpc • ICL have similar ages • Comparable or more metal poor than stellar envelopes at 10-30 kpc Gu et al. 2018c in prep.

Age and Metallicity of Stars in the ICL • Compare age and [Fe/H] of ICL to the dwarf ETGs in Coma - Stars in the ICL are similar to the current dwarf ellipticals (~10 9 Msun) Gu et al. 2018c in prep.

Age and Metallicity of Stars in the ICL • Compare age and [Fe/H] of ICL to the dwarf ETGs in Coma - Stars in the ICL are similar to the current dwarf ellipticals (~10 9 Msun). - The two BCGs have richer accretion histories than average. Gu et al. 2018c in prep.

Summary The cluster center shapes the [ α /Fe]– σ ⋆ and [ α /Fe]– M ∗ relations • differently than other environments. Coordinated assembly of BCGs : their building blocks are different from • the general low mass populations by their high [ α /Fe]. Age, [Fe/H] and σ radial profiles extended to 200 kpc. They are • consistent with the coordinated assembly picture. Age and [Fe/H] in the ICL are similar to the outskirts of massive ETGs • and dwarf ellipticals. Next Steps Stellar Population of the ICL across z=0.1-0.5 using integrated field • spectroscopy (e.g. MUSE) The Stellar Initial Mass Function in the Coma ETGs •