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Scaling Rela+ons of Early Type Galaxies in Virgo Chin-‐Wei Chen (NCU, Taiwan), (ASIAA, room1202, in the front of 12F elevator) Patrick Cote (HIA, Canada), Andrew A. West (BU, USA), Eric W. Peng (KIAA, China), Laura Ferrarese (HIA, Canada)
2010, ApJS, 191, 1
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Outline
• Introduc+on: Dwarf-‐Giant dichotomy • Data and analysis on 100 ACSVCS galaxies • Result: Comparison with the literature Scaling rela+on (Re -‐ mag, and <μe> -‐ mag) Color-‐mag rela+on
• Conclusion and Summary • Ongoing Project: Op+cal Proper+es of BCGs
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Introduction • Understanding the physical process that shaped the structure of nearby galaxies is a key goal of modern astrophysics. This goal, has proved challenging for early type galaxies which are historically believed to exhibit puzzling structural dichotomy.
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n Dichotomy: Any spli\ng of a whole into exactly two non-‐overlapping parts (h]p://en.wikipedia.org/wiki/Dichotomy)
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Dwarf-‐Giant Dichotomy (Kormendy, 1985)
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Dwarfs
Ellipticals
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Early type galaxies were divided into two, non-‐overlapping popula+ons that originated through fundamentally dis+nct forma+on channels (Kormendy, 1985).
Dwarf-‐giant dichotomy:
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However
• Sample selec+on and choice of model describing the underlying light profile may bias the scaling rela+on! (e.g., Graham et al. 2003; Graham & Guzman 2003; Gavazzi et al. 2005; Ferrarese et al. 2006; Misgeld et al. 2008, 2009; Janz & Lisker 2009; Glass et al. 2011 )
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Main purpose of this study Whether or not the giant-‐ellip2cals and dwarfs distribute smoothly along the scaling rela2on ????
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Facts of Virgo Cluster:
n 16.5 Mpc, n Abell richness class=I n Virial mass~4x1014M⊙ (Girardi et al. 1995) n 2096 cataloged galaxies (Binggeli et al. 1985) n Subcluster A: M87 n Subcluster B: M49
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• Subcluster A
M87
§ Deep V band image for 2.25 deg2 § 1 sigma Depth of 28.5 mag § +dal features reflect the
hierarchical nature for cluster assembly
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M49
M87
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ACS Virgo Cluster Survey n θ: 0.1” è 8 pc at a distance of Virgo
n FOV ~ 200”x 200”
n F475W and F850LP band (g and z) photometry were obtained for 100 early-‐type galaxies
n 100% complete for BT≦12 mag and ~60% complete for early-‐type galaxies brighter than BT=16 mag
The first study to examine simultaneously the core and global structure of a large sample of nearby galaxies using HST image (Ferrarese et al, 2006). 1. Sersic family è good representa+on! 2. Dwarfs formed a low luminosity extension to the giant ellip+cals è Successful models for small-‐scales structure froma+on should yield galaxies having their structural and photometric proper+es vary smoothly along the luminosity func+on.
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n Choice of galaxy model + limited ACS FOV???
Verify that the recent progress on the scaling rela+on of early type galaxies are robust to the choice of galaxy model. è non-‐parametric approach Whether FOV limita+on of ACSVCS has any significant effect on the derived parameters for ACSVCS galaxies. è Sersic fit on SDSS photometry
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Data and Analysis (1/2)
n Construc+on of SDSS mosaics (West et al. 2010) the sky is fi]ed with a +lted plane è final mosaics with zero sky and non-‐masked sources. 1dx1d for the five brightest galaxies, 30’x30’ for the 6th to 20th ranked galaxies and 10’x10’ for the remaining.
n Source Masking
16 VCC 1025 r
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2Rp
R50
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Measurement of Photometric and Structural Parameters:
n Parametric-‐-‐-‐-‐-‐-‐ Sersic model (Sersic 1968)
Ie: effec+ve surface brightness
ns: Sersic Index (bn= 1.9992ns-‐0.3271) (ns=1 for exponen+al, ns=4 for de Voucouleur)
Re: effec+ve radius
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u g r i z gacs
u-g g-r g-I g-z
n=5.43
n=4.69
n=2.35
n=1.83
n=1.51
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Non-‐parametric: Curve-‐of-‐growth photometry
Petrosian radius, Rp: Qp(Rp)=0.2 Petrosian Flux, Fp:
Petrosian ra+o, Qp:
Total luminosity, Re, <μe>
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Comparison to Previous Results
: E
: S0
: dwarf
: E
: S0
: dwarf
The SDSS Sersic fi\ng is in good agreement with ACS result.
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: E
: S0
: dwarf
The SDSS COG parameters is in good agreement with Janz & Lisker (2008).
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: E
: S0
: dwarf
The SDSS COG analysis is in good agreement with VCC (Binggeli et al. 1985) and ACS result.
• It is possible to measure the basic parameters of nearby early-‐type galaxies with quite reasonable accuracy: ground based vs HST and non-‐parametric vs parametric
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Photometric and Structural Scaling Rela+ons: The Role of Environment
: E
: S0
: dwarf
n The rela+onship between Mg, re, and < μ >e shows that the parameters vary smoothly as a func+on of luminosity è dose not favor the dwarf-‐giant dichotomy.
n Tidal stripping has been playing an important role during the forma+on/evolu+on of the cEs.
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The Color-‐Magnitude Rela+ons
: E
: S0
: dwarf
n The CMR is non-linear but has smooth distribution.
n Faint systems have larger scatters.
Chen et al. 2010
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: E
: S0
: dwarf
n Comared with single-burst stellar population synthesis models from Bruzual & Charlot (2003), Chabrier (2003) IMF, are show for metallicities and ages.
n For the low mass systems, we see larger dispersions in both age (2Gyr -12 Gyr) and metallicity ([Fe/H]=-0.7 to 0 dex)
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Conclusion and Summary n Our non-‐parametric measurements and those from the
literature are in good agreement. n The rela+onship between g-‐band mag, Re and <μe> shows
that the parameters vary smoothly and systema+cally as a func+on of luminosity.
n Galaxy colors show a non-‐linear but smooth varia+on with luminosity. The color-‐magnitude extends smoothly across the region normally taken to separate “giant” galaxies from “dwarfs”. There is clear evidence for enhanced sca]er in color for the faintest systems-‐-‐-‐presumably the signature of more diverse star-‐forma+on histories among the lowest-‐mass galaxies.
n Next Genera+on Virgo Cluster Survey (Dec 2008-‐Jun 2012)
Op+cal Proper+es of Brightest Cluster Galaxies with PanSTARRs
Medium Deep Survey
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Chin-‐Wei Chen (ASIAA, Taiwan), Lihwai Lin (ASIAA, Taiwan), Hung-‐Yu Jian (NTU, Taiwan), Sebas+en Foucaud (NTNU, Taiwan)
Introduc+on • Brightest Cluster Galaxies: The most luminous galaxies locate in the center of clusters or groups of galaxies.
• Simula+on performed in a hierarchical context predic+ng that BCGs are the result of mul+ple mergers and should con+nue to grow un+l z~0.5 (De Lucia and Blaizot, 2007)
• Observa+onally, BCGs are found to evolve passively since z~1 (Sto] et al. 2008, 2010; Whiley et al. 2008; Collins et al. 2009)
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PanSTARRs § 1x1.8m @ Mt. Haleakala, Maui
§ bands: g, r, i, z, y
§ May, 2010 to end of 2013
§ FOV: 7 deg2 field of view, making it one of the widest digital sky survey facility to date.
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PS1 Medium Deep Survey § Over 80% of the PS1 survey +me was a]ributed to two
strategies -‐-‐-‐ the 3-‐Pi and the medium deep (MD) survey. The main goal for 3-‐Pi survey is to have large sky coverage and will eventually cover ¾ of the sky. The MD survey is for deeper photometry on smaller frac+on of the sky.
§ We study galaxy proper+es in clusters based on the stacking of MD survey images, which consists of 10+1 fields with extensive photometric/spectroscopic study from space or ground-‐based observa+on.
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PS1 Medium Deep Survey
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Field Alt Name RA (J2000) Dec (J2000)
MD00 M31 00 42 42 +41 16 00
MD01 XMM-LSS-DXS/VVDS-02h 02 23 30 -04 15 00
MD02 CDFS/GOODS/GEMS 03 32 24 -27 48 00
MD03 IFA/Lynx 08 42 22 +44 19 00
MD04 COSMOS 10 00 00 +02 12 00
MD05 Lockman-DXS 10 47 40 +58 05 00
MD06 NGC 4258 12 20 00 +47 07 00
MD07 DEEP2-Field 1/ Extended Groth Strip
14 14 49 +53 05 00
MD08 ELAIS-N1-DXS 16 11 09 +54 57 00
MD09 SA22-DXS/VVDS-22h 22 16 45 +00 17 00
MD10 DEEP2-Field3 23 29 15 -00 26 00
Image Quality Assessment of PS1 MD fields
• 1.5 year observa+on (g, r, i, z, y) depth = (25.069, 24.944, 24.684, 24.346, 22.759)
• Mock catalog based on Millennium N-‐Body Simula+on Detec+on of 147,000 galaxies per MD field (some 1000 clusters/groups with mass > 1013 Ms per MD field )
• Deep Stacks images è Photometric z + Probability Friend-‐of-‐Friend è BCG study
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PS1 images for MD04 X-‐ray selected cluster of galaxies
• XMM-‐COSMOS cluster galaxy catalog (George et al. 2011) running via PFOF
• 26/26 X-‐ray selected galaxy clusters were recovered. 18/26 matches of the BCGs.
41 Z=0.425 Z=0.359 Z=0.735
Prospects
• In addi+on of the PS1 grizy photometry, we are also producing on the stacks of CFHT u-‐band data for MD fields. An approximate es+ma+on for its depth is ~ 26 mag.
• MD07 done, MD04, MD10 in process • The u band photometry provides be]er constraints on the photometric redshi~s for galaxies with z < 0.4.
• Probe the recent star forma+on ac+vi+es in galaxies with z ~ 0.7 by studying u-‐op,cal colors.
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Stay Tuned~~
