are galaxies still evolving strongly? christopher j. miller hubble heritage image
TRANSCRIPT
Are galaxies still evolving strongly?
Christopher J. Miller
Hubble Heritage Image
Part I
Defining the questions, methods, and tools of the research topic
Physical Processes ofGalaxies
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.
Field
Cluster
Ram Pressure Stripping
StrangulationInteraction
White et al.
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Galaxy Properties
Star-Formation History
Bianchi et al., Condon et al., and others
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.
Active Galactic Nuclei
vs.
Miller et al. 2003
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
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……
Concentration Index(poor man’s morphology)
Goto et al.
Galaxy Environments
Density Estimation
sdss.org
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
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
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.
Part II
What do we already know?
Star-Formation vs. Environment
Gomez, Nichol, Miller et al.
Balogh, Eke, Miller et al.
AGN fraction vs. Environment
Miller et al. 2003
Caution: Concentration Index is not a great morphology indicator (cannot separate E/S0’s for instance).
Star-formation and Clusters:
Field
Miller et al. in prep.Gomez, Miller, Nichol et al.
Part III:
A new research topic:
Phenomenological Studies of Brightest Cluster Galaxies
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
The SDSS-C4 Cluster Catalogwww.ctio.noao.edu/~chrism/C4Miller et al. 2005, AJ, 130 968
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
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
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
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)
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
Example High Density BCGs
Example Low Density BCGs
X-ray BCGsPSPC SDSS RASS
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
Results Part 2:
• X-ray detected clusters favor the BCGs in the highest density regions.
• Indicates a possible bias in BCG cluster studies.
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.
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.
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