are galaxies still evolving strongly? christopher j. miller
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The Effects of Environment. Hubble Heritage Image. On Galaxy Evolution at Low-z. Are galaxies still evolving strongly? Christopher J. Miller. Part I. Defining the questions, methods, and tools of the research topic. Physical Processes of Galaxies. Galaxy Interactions. - PowerPoint PPT PresentationTRANSCRIPT
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Are galaxies still evolving strongly?
Christopher J. Miller
Hubble Heritage Image
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Part I
Defining the questions, methods, and tools of the research topic
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Physical Processes ofGalaxies
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Galaxy Interactions
• Few collisions, lots of interactions, but “horsehoes and handgrenades”
• ~ energy 108 -109 Supernovae• Quick, ~108 Years• Relatively rare (in recent times) 1-
5% maybe. Hard to measure.• Very, very hard to define
(observationally)• Field Galaxies undergo mergers
Hibbard
Hibbard and Barnes
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Ram Pressure Stripping
• Galaxies fall (gravitationally) through the hot intracluster gas.
• 107 K, 10-4cm-3
• Hydrodynamic and Nbody simulations
• Mapping of gas content in Virgo spirals shows the HI disks to be highly disturbed, but the molecular content unchanged.
• Galaxies undergo ram pressure stripping when in the cores of clusters
• Slower than colliding galaxies
Vollner (Strasbourg)
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Strangulation
• Halos are gradually (Gyrs) removed from disk galaxies
• Lack of fuel only changes the star-formation properties (not necessarily the morphologies)
Goto et al.
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Field
Cluster
Ram Pressure Stripping
StrangulationInteraction
White et al.
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Galaxy Properties
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Star-Formation History
Bianchi et al., Condon et al., and others
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SFR Indicator
PRO CON
UV cont.Glow of young stars
Young stars, large z-range and evolution.
patchy extinction (0-3), IMF-- high stellar masses (>5). Population age dependent
H EWnebular lines re-emit the stellar luminosity
Coupling between nebular emission and SFR. Spatial mappings. Well-defined, easy to measure.
Instantaneous, massive SFR ((>10). Extinction (1). Assumes SF traced by ionized gas. IMF.
[OII] EWforbidden line
Good to high-z. Not strongly dependent on metal abundance. Easy to measure.
Excitation difference, not tied to ionizing luminosity. IMF. Extinction (0-2)
FIRabsorption by dust, re-emitted in IR.
Ideally the ultimate SFR indicator. SIRTF. Weak extinction.
Dust can also be heated by older stars (at 100um). Dependent on galaxy type. IMF.
RadioSynchrotron and free-free emission from HII
Sub-arc second resolution. Since from SN, trace young stars. Weak extinction. Tight FIR/Radio correlation
Connection between SF and synchrotron not well understood. IMF.
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Active Galactic Nuclei
vs.
Miller et al. 2003
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Morphology
Elliptical
E0 E6
S0 Sa Sb Sc
S0a SBa SBb SBc
Elliptical
Lenticular Spiral Spiral Spiral
BarredLenticular
Barred Spiral
BarredSpiral
BarredSpiral
Irregular
IrrFaulkes Telescope Project
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Bulge-to-Disk Ratio
Standard Bulge-to-Disk code takes ~2 minutes per galaxy (GIM2d).
Need to get to at least seconds per galaxy to do large datasets. Close……
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Concentration Index(poor man’s morphology)
Goto et al.
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Galaxy Environments
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Density Estimation
sdss.org
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Kernel vs. Nearest-NeighborDensity Estimation
• Fixed Kernel Width is well-studied in the mathematical literature.
• Higher-order bias• Use cross-validation
to find the “optimal” aperture.
• But still, does one aperture size suit all?
• Also well studied in the mathematical literature.
• Common in past astrophysical research
• Variable kernel size• low-order bias• Never converges to
the “truth”
Kernels
Nearest Neighbors
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Galaxy Clusters
• We use the SDSS-C4 galaxy cluster catalog
• >90% complete, <5% contamination for M>2x1014 solar
• Clusters identified and studied in the spectroscopic sample
• >250 clusters in ~1000 sq. degrees
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Summary: Part I
• Galaxy interactions, ram pressure stripping and strangulation affect the properties of galaxies.
• Such properties include star-formation rate, AGN activity, and morphology.
• By measuring the environment around every galaxy, we can try to isolate which of the above processes affect which of the above properties.
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Part II
What do we already know?
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Star-Formation vs. Environment
Gomez, Nichol, Miller et al.
Balogh, Eke, Miller et al.
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AGN fraction vs. Environment
Miller et al. 2003
Caution: Concentration Index is not a great morphology indicator (cannot separate E/S0’s for instance).
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Star-formation and Clusters:
Field
Miller et al. in prep.Gomez, Miller, Nichol et al.
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Part III:
A new research topic:
Phenomenological Studies of Brightest Cluster Galaxies
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Doing Research the “VO way”
• Start with an idea– E.g., galaxy properties as a function of
environment.– Brightest Cluster Galaxy properties and their local
environment
• Explore– What images and/or catalogs are available?
• Trial run– Start small
• Production mode– Grow with time and code to re-run on newer,
bigger, better data in the future.
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ExploreQuickTime™ and aTIFF (Uncompressed) decompressor
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Inventory: What will we need?
• Data– Clusters (centers, masses, shapes, BCG)– Galaxy magnitudes, colors, shapes– Gas (X-ray) fluxes, extents
• Functions/Tools– Luminosity distances, absolute magnitudes, k-
corrections, angular diameters, statistical tools, plotting techniques, image display
• Services– Skynodes, Coneservices, SIAP services, Registry
Trial R
un
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The SDSS-C4 Cluster Catalogwww.ctio.noao.edu/~chrism/C4Miller et al. 2005, AJ, 130 968
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Get the SDSS Data
radius = zang(radius_fixed,c4data[I].z)/60.0 ; In arcminutes
siapcall,c4data[I].ra_bcgphot, c4data[I].dec_bcgphot, radius/60.0, $url=“http://casjobs.sdss.org/vo/DR4SIAP/SIAP.asmx/getSiapInfo?&FORMAT=image/jpeg” + $ “&BANDPASS=*&", root="images/sdss_c4_"+strtrim(string(c4data[I].cluster_id),2)
qry = " SELECT o.ra,o.dec, o.expAB_r, o.isoPhi_r " " FROM SDSSDR2:PhotoPrimary o " + $ " WHERE o.type = 3 AND o.petroMag_r < 23.0 " + $ " AND Region('Circle J2000 " + strtrim(string(c4data[I].ra_bcgphot,format='(f10.3)'),2) + $ " " + strtrim(string(c4data[I].dec_bcgphot, format='(f10.3)'),2) + $ " " + strtrim(string(radius, format='(f4.2)'),2) + "') ”
skyclient, qry=qry,str=sdss_gals
separ, sep, c4data[i].ra_bcgphot, sdss_gals.sdssdr2_ra, $ c4data[i].dec_bcgphot, sdss_gals.sdssdr2_dec
min = min(sep, minit)
Get the images
Get the catalog data
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Get the SDSS-2MASS Matches
qry = " SELECT o.ra,o.dec, o.modelMag_u, o.modelMagErr_u, o.modelMag_g,” + $ “ o.modelMagErr_g, o.modelMag_r, o.modelMagErr_r, o.modelMag_i, o.modelMagErr_i, “ + $ “o.modelMag_z, o.modelMagErr_z, o.extinction_u, o.extinction_g, o.extinction_r, “ + $ “o.extinction_i, o.extinction_z, t.j_m, t.k_m, t.h_m, t.j_msigcom, t.k_msigcom, t.h_msigcom " + $ " FROM SDSSDR2:PhotoPrimary o, TWOMASS:PhotoPrimary t " + $ " WHERE XMATCH(o,t)<" + strtrim(string(chisq),2) + " " + " AND o.type = 3 " + $ " AND Region('Circle J2000 " + strtrim(string(c4data[I].ra_bcgphot,format='(f10.3)'),2) + $ ” " + strtrim(string(c4data[I].dec_bcgphot, format='(f10.3)'),2) + $ " " + strtrim(string(radius, format='(f4.2)'),2) + "') "
skyclient,qry=qry,str=sdss_2mass_gals
Get the 2MASS-SDSS cross matches
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Get the X-ray data
conecall, c4data[I].ra_bcgphot, c4data[I].dec_bcgphot, radius/60.0, str=str, $ url = "http://heasarc.gsfc.nasa.gov/cgi-bin/vo/cone/coneGet.pl?table=wgacat&r"
conecall, c4data[I].ra_bcgphot, c4data[I].dec_bcgphot, radius/60.0, str=str, $ url = http://heasarc.gsfc.nasa.gov/cgi-bin/vo/cone/coneGet.pl?table=xmmssc& sizeit = size(str);If there is XMM-SSC data, get the image IF (sizeit[1] gt 1) THEN BEGIN separ, separ, c4data[i].ra_bcgphot, str.ra, c4data[i].dec_bcgphot, str.dec min = min(separ, minit) bcg_EP[I] = str[minit].ep_flux IF not (keyword_set(nosiap)) THEN siapcall,c4data[I].ra_bcgphot, c4data[I].dec_bcgphot, 0.1, $ url="http://xsa.vilspa.esa.es:8080/aio/jsp/siap.jsp", $ root="images/xmm_bcg_c4_"+strtrim(string(c4data[I].cluster_id),2), /metadata,str=str ENDIF
Get the WGACAT sources
If a WGACAT source exists, get the PSPC image
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Calculate the Absolute Magnitudeskcorrect,mags, magerrs, zs , kcorr, filterlist=filterlist, band_shift=0.0
bcg_absJ[I] = sdss_2mass_gals[minit].twomass_j_m - kcorr[5,minit] (5*alog10(lumdist(c4data[I].z)*1e6) + 5)
mR = MQ + DM(z) + KQR(z),
where mR is the apparent magnitudeMQ is the absolute magnitudeDM(z) is the distance modulus, accounting angular diameter distance and cosmological surface-brightness dimmingKQR(z) is the K-correction.
See: http://cosmo.nyu.edu/blanton/kcorrect/v3_2-index.htmlSee: Hogg et al. (2002)
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plot, -(bcg_isophi[wkeep]-90),c4data[wkeep].ang1000, psym=4, $ xtitle="BCG Position Angle (degrees)", $ ytitle="C4 Cluster Position Angle (within 1Mpc) (degrees)"
h = histogram(abs(-(bcg_isophi[w]-90)-c4data[w].ang1000),omin=omin, binsize = 5)plot, 5*findgen(n_elements(h)) + omin, h, psym=10
kstwo, delta_phi, zran,d,prob
result = r_correlate(-(bcg_isophi[w]-90), c4data[w].ang1000)
Finally: AnalyzeMake Plots
Look for correlations
Make Histograms
Run statistical tests
Look at th
e BCGs
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Example High Density BCGs
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Example Low Density BCGs
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X-ray BCGsPSPC SDSS RASS
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Results Part 1:
• Statistical tests indicate a ~2 result that the BCG PA is aligned with the cluster PA.
• BCG ellipticity shows no significant dependence on local density
• BCG colors are 2 tenths bluer in the density regions.
• BCGs luminosity shows no significant dependence on local density
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Results Part 2:
• X-ray detected clusters favor the BCGs in the highest density regions.
• Indicates a possible bias in BCG cluster studies.
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Understanding BCG Evolution
• Lin and Mohr (2005) find evidence that BCGs grow over time and are more massive in the more massive clusters.
• Andernach et al. (2006) find BCG ellipticity decreases with cluster mass
• Harris et al. (2006) use ACS/WFC to discover strong color gradients in BCGs (old red star clusters live in the centers).
• Brough et al. find that X-ray the brightest luminous clusters have BCGs with shallow light profiles (more collisions).
• All of the above are consistent with bottom up hierarchical growth and inconsistent with top-downSee also Laine et al. (2003)
• Haruyoshi et al. (2003) find that BCG luminosities not correlated with the underlying viral density
• Collins et al. (2003) find that BCGs in high Lx clusters show no mass growth.
• Egami et al. (2006) suggest BCGs are star-forming (IR)
• Nelson et al. (2002) find that BCG sizes using NICMOS are the same size at z>0.5 as they are z=0. They find smaller radii at z=0.5 with WFPC2.
• All of the above are consistent with monolithic collapse.
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Our New Conclusions• Given a starting point (re: Inventory and plan, tools), we can
easily do and re-do research without having the majority of the data on our hard disks.
• In this case, we collected SDSS optical, 2MASS infrared, and X-ray images and catalog data for a sample of 300 BCGs in the SDS C4 cluster catalog
• We found (weak) evidence that the position angle of the BCG is aligned with the PA of the cluster.
• We find a small fraction 5-10% of our BCGs have very high local densities.
• We find a significant trend in bluer BCGs having higher local densities.
• Hypothesis: these are younger BCGs in younger systems, still under-going collapse.
• More questions to answer.
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Useful Sites:
• www.ctio.noao.edu/~chrism/VOlib• www.ctio.noao.edu/~chrism/C4• www.nvo.noao.edu• www.us-vo.org• http://us-vo.org/summer-school/2005/proceed
ings/presentations/miller/cluster_science.html