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The Star Formation- Density Relation …and the Cluster Abell 901/2 in COMBO-17. Christian Wolf (Oxford) Eric Bell, Anna Gallazzi, Klaus Meisenheimer (MPIA Heidelberg) Alfonso Aragon-Salamanca, Meghan E. Gray, Kyle Lane (Nottingham). Morphology-Density Relation. Morph-density relation - PowerPoint PPT Presentation
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The The Star Formation-Star Formation-Density Relation Density Relation
…and the Cluster Abell 901/2 in COMBO-17…and the Cluster Abell 901/2 in COMBO-17
Christian Wolf (Oxford)
Eric Bell, Anna Gallazzi, Klaus Meisenheimer (MPIA Heidelberg)
Alfonso Aragon-Salamanca, Meghan E. Gray, Kyle Lane (Nottingham)
Morphology-Density Relation
• Morph-density relation– Present when averaged
over age/colour (Dressler 1980)
– No such relation • at fixed colour or age
(Ball, Loveday & Brunner 2006;
Wolf et al. 2007) • at fixed mass
(Kauffmann et al. 2004)
• SFR-/Age-density relation– Yes: at fixed mass
(Balogh et al. 1999; Kauffmann et al. 2004; Poggianti et al. 2006)
– Yes: at fixed morphology(Wolf et al. 2007)
Morphology-Age-Density
Wolf et al. 2007
• Age-density relation for ageing (E-Sb) galaxies• Age-morphology relation for fixed density (obvious?!)• No Morphology-density relation at fixed age
SF-Density () Relation
Gomez et al. 2002 (SDSS)
Kodama et al. 2001
Lewis et al. 2002 (2dF)
…or nurture?
– Stripping (Ram press., Gun & Gott 72)
– Excitation (Tidal of burst, Bekki 99)
– Harassment (Moore et al. 1999)
– Mergers (Major, Barnes 1992)
– Suffocation (Larson 1980)
– Strangulation (Balogh et al. 2000)
Nature?– Internal
feedback (SN, AGN)
SF-Density Relation Across Z
• Present-day SF-density– Optical SF indicators
• GOODS (Elbaz et al. 2007)
– z~1, includes obscured SF
– SF peaks at higher density
• Semi-analytic simulations– Typically include mergers,
but no environment physics– Recent work: IGM heating
+ ram-pressure stripping(Khochfar & Ostriker 2007)
Low-Z incl. Obscured SF
• Obscured SF: different result
from UV-optical indicators– COMBO-17 A901 + MIPS
– Obscured SF continues into high-density regions
– Not very different to z~1
• Which galaxies make the difference?– See dusty red galaxies
(Wolf, Gray & Meisenheimer 2005)
(MB<-20)
A901Gallazzi et al., in prep.
λ / nm
QE (
%)
COMBO-17 on A901 Complex
• Disturbed evolving cluster Abell 901a/b & 902– Galaxy transformation
during plenty of infall action
– 800 cluster members with MV < -17.8 and z ~ 0.006
5 Mpc
Old Red / Dusty Red @ z=0.17
Age
Dust
Old red
Dusty red
~150 atMV<-18
Wolf, Gray & Meisenheimer 2005
Mean Spectra
Type-Density RelationDusty red galaxies:
• Intermediate ages• Intermediate density• Intermediate luminosity• Intermediate morphology
• Non-virialized kinematics infall population?
WGM 2005
Optically Passive Spirals!
old
dusty
blue
E S0 Sa Sb Sc Sd Irr
The STAGES collaboration
• Passive spirals(Poggianti et al. 1999; Goto et al. 2003) – Spectra & colours:
Lack of star formation– Cluster infall regions– Might be intermediate stage
from spiral to S0
• A901 dusty red galaxies (Wolf, Gray & Meisenheimer 2005)
– 35%(!) of red members
• Red star-forming galaxies(Miller & Owen 2002, Coia et al. 2005) – Radio; ISO 15– Outskirts of merging cluster
SFR: UV-opt. vs. Obscured
Dust Extinction & IR/UV Ratio
Dusty Red = “Transition” Population
Dusty red galaxies in A901• are semi-suppressed in star formation• have star formation obscured to highest degree• star formation obscuration ~ stellar light obscuration
All galaxies appear to follow a 2 Gyr exponential SFR decline
IR-Semi-Passive Galaxies
• Transition galaxies– IR-semi-passive spirals≈ 1/2-dex-reduced central
dust-extinguished SF– No burst upon infall– No sign of major mergers– No truncation (H weak)
• Where found?– In three complex merging
cluster environments(so far)
• Star formation budget– Fraction of obscured SF
increases in infall region– Small on cosmic scale– Relevant for role of
environment– Continued central SF
may continue bulge growth
Suggestions: Observations
• Quenching Timescale?– High-S/N spectra + SED– Recent SF History
• More (super-) clusters?– Density is not only factor– 2nd parameter: “Stage”
of infall, cluster merging?– Optical SED sufficient(?)– Need:
• Redshift coverage
• Range of environments
• Accurate dust estimates or Mid-IR imaging
• Medium-band photo-z’s or spectroscopy
• 80 orbit mosaic
• ACS + WFPC2/NIC3 parallels
• multiwavelength follow-up from X-ray to radio
• primary science aim: galaxy evolution as a function of environment image: COMBO-17 contours: mass
Space Telescope A901/902 Galaxy Evolution Survey
Ratio Spectrum: Dusty/Old
WGM 2005
Selecting The Cluster Sample
zphot = 0.170 ± 0.006 795 galaxies within cz = 1900 km/s 1575 = 3.7 x 3.5 x 120 (Mpc/h)3
Luminosity Distribution
2-D Clustering
Old red = cluster coresDusty red ~ blue cloud
(x,y): old red = cluster coresdusty red ~ blue cloud
(y,z): old red ~ dusty redblue cloud = ‘voids’
v ~ 550 km/sv ~ 1400 km/s