askap continuum s urveys of local galaxies
DESCRIPTION
ASKAP Continuum S urveys of Local Galaxies. Michael Brown ARC Future Fellow Monash University. Where are we now?. NVSS / FIRST / SUMMS 0.5 mJy RMS per beam 15”-1’ beam ~30 uJy RMS per beam in 12 hours . Future ASKAP 12. KTRANSCRIPT
ASKAP Continuum Surveys of
Local Galaxies
Michael BrownARC Future FellowMonash University
Where are we now?
• NVSS / FIRST / SUMMS• 0.5 mJy RMS per beam• 15”-1’ beam
• ~30 uJy RMS per beam in 12 hours Future ASKAP 12
K<9 Spiral Galaxies
Catalogued sources
Flux density perbeam from NVSS images
K<9 Early-type Galaxies
Brown et al. 2011
K<10.5 Spiral Galaxies & AGNs
Floyd et al. (submitted)
Radio continuum• Continuum detects “hot mode” AGNS.• Continuum can be a good SFR indicator
– Have we been misled by optical colours?– Are SFR indicators properly calibrated?
• ASKAP ADE-12 is great for low z science!– It will detect all* local galaxies (duty cycles, env).– One galaxy per beam and with known locations.– Spectroscopy, morphology, optical, mid-IR
• Done better with completed ASKAP but…
Galaxy Colour Bimodality
Galaxy Evolution
Bonne et al. (in prep.)
K-band Absolute Magnitude
Red
Spi
ral /
Tot
al S
pira
l
Kennicutt et al. 2009 Corrected L Ha
L 1.4
L 1.4 & L Ha
SFRIndicator
RescalingSpectra
Spectra and H-alpha measurements from Moustakas et al. (2006, 2010) need to be increased by 10%.
UGCA 219
NVSS 4.5 mJy Optical g=14.78
UGCA 166 g~16
NVSS 2.0 mJy Optical g=16.05
Dolley et al. (in prep.)High star-formationLow star-formation
Gal
axy
Clu
ster
ing
Stre
ngth
Projected spatial Scale
Are Red Spirals Forming Stars?
• KAB<10.5 spiral galaxies– Bonne et al. (in prep) and Floyd et al. (sub.)
• NVSS 1.4 GHz as a star formation proxy– 1.4 GHz is not impacted by dust obscuration
• WISE mid-IR to search for warm dust– Dust is heated by star formation
• 21-cm to search for neutral hydrogen– Could star formation resume?
Sample SelectionKAB<10.5T-type > -1NVSS 1.4 GHz coverage228 galaxies
Select galaxies with f1.4 < 2.5 mJy42 galaxies
SDSS Optical Colours
KAB<10.5 f1.4<2.5 mJyAll other spiral galaxies
UV-optical similar to passive E
H-alpha lost in the noise
Spiral arms are blue in UV-optical
IR excess
Red and no NVSS, but Star Forming
Radio continuum• Continuum detects “hot mode” AGNS.• Continuum can be a good SFR indicator
– Have we been misled by optical colours?– Are SFR indicators properly calibrated?
• ASKAP ADE-12 is great for low z science!– It will detect all* local galaxies (duty cycles, env).– One galaxy per beam and with known locations.– Spectroscopy, morphology, optical, mid-IR
• Done better with completed ASKAP but…
NGC 2811 f1.4 < 2.5 mJy
X
Summary• Have we been misled by colour bimodality?• Red spirals are not faded blue spirals.
– Red spirals are brighter than blue spirals (Bonne).• High and low SFR spirals live in similar halos
– The large-scale clustering is similar (Dolley).• Low SFR spirals are not passive spirals
– Infrared excess and PAH emission • Red spirals generally have HI
NVSS WISE 11 microns
Spitzer 24 microns SDSS Optical
Infrared SEDsIR excess relative to passive elliptical galaxies
NGC 4725 spectrum shows PAH and dust emission
21-cm
Catalogued HI in redUncatalogued HI in black
228 spirals with KAB < 10.5186 spirals in HI catalogues
42 spirals f1.4 < 2.5 mJy31 spirals in HI catalogues
NGC 5188 f1.4=95 mJy
X
NGC 7727 f1.4<2.5 mJy
X