The SEDs of Interacting Galaxies
Lauranne LanzNicola Brassington, Andreas Zezas, Howard A. Smith, Matthew L. N. Ashby,
Elisabete da Cunha, Christopher Klein, Patrik Jonsson, Chris HaywardLars Hernquist, Giovanni Fazio
Harvard-Smithsonian Center for [email protected]
NGC 520:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Outline
• What is Spitzer Interacting Galaxy Survey (SIGS)?
• SED shapes• SED fitting• sSFR comparisons• Trends with interaction stage
N3226-N32273.6 µm, 4.5 µm, & 8 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection• Keel-Kennicutt (Keel et al. 1985) “complete” and
“Arp” samples:– Selected based on association likelihood– Require |Δv|< 600 km s-1 to remove non-associated pairs
• Imposed distance constraint cz < 4000 km s-1
• Resulting sample: 111 galaxies in 50 systems
NGC 2976:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Observations
• Complete Spitzer coverage: – IRAC, MIPS, and nuclear IRS spectra
• Almost complete GALEX coverage• Some Herschel coverage• Ancillary data– WISE coverage– Some Chandra/XMM coverage– Hα fluxes
M51NUV, IRAC 3.6 µm, & SPIRE 250 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection and Observation Set Benefits
• Not morphologically selected: large range of interaction parameters
• Not infrared selected: less active systems included• Not based on optical line diagnostics• UV and IR coverage gives complete SFR
NGC 470 & NGC 474:FUV, 3.6 and 4.5 µm, & 8.0 µm
NGC 520:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Example: M51 and NGC 3430/3424
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry
• S-Extractor used to determine NUV and 3.6 µm apertures
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry
• S-Extractor used to determine NUV and 3.6 µm apertures
• Fluxes determined in larger aperture in all bands• Uncertainty: Calibration and Poisson
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
SED shapes
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
M51 A
NGC 3424 NGC 3430
M51 B
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Two blackbodies + β=1.5 graybody
4367 K 356.2 K 28.6 K 4058 K 357.1 K 25.8 K
3572 K 303.5 K 29.2 K 3307 K 339.5 K 25.2 K
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
M51 A
NGC 3424 NGC 3430
M51 B
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
MagPhys SED-fitting Code
• Optical stellar from Bruzual & Charlot 2003 and infrared dust from da Cunha, Charlot, & Elbaz 2008 spectral libraries
• Energy absorbed in UV/optical is re-emitted in IR• No AGN contribution considered• Likelihood distributions constructed for model
parameters to determine best fit SED
Elisabete da Cunha’s talk this afternoon
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDsLo
g( λ
L λ /
L )
Log(
λL λ
/ L
)
sSFR
TwarmTcold
sSFR
TwarmTcold
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDsLo
g( λ
L λ /
L )
Log(
λL λ
/ L
)
sSFR
TwarmTcold
sSFR
TwarmTcold
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit comparisonsFIR β=1.5 gray-body temperature falls between SED-fitted warm and cold temperatures
The integrated 8-1000 µm 3-component fit agrees well with the dust luminosity determined from fitting the SED.
Log( LDust, SED / L) F
rac.
Diff
eren
ce
Log
( L8-
1000
µm, 3p
art /
L)
TWarm
TCold
TGraybody / K
T SED
/ K
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Log(sSFR/yr-1) SED Fitting
Log(
sSFR
/yr-1
) Pre
scrip
tion
Comparison of Specific Star Formation Rates
M51A
N 3430
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary• SIGS will provide a sample of interacting
galaxies from first pass to coalescence with a range of interaction parameters.
IC 1801 and NGC 935NUV, 3.6 and 4.5 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary• With the first 10 groups with SPIRE data, we:– find a range of SED shapes, especially in the ratio
of MIR to optical/UV.– measured sSFR and temperatures using the
MagPhys (da Cunha et al. 2008) SED-fitting code.– find an increase in warm component temperature
with interaction stage, but no significant change in sSFR.
M81:NUV, 8.0 µm, & 250 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Thank you for the attention and stay tuned for more:• 40 more interacting groups
• Nuclear activity• Comparison with simulated systems
N3448 – U6016:FUV, 3.6 µm, 4.5 µm, & 8 µm
M101:NUV, 3.6 µm, & 8 µm
Cox et al. 2006
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011