Day 632

Saturday.

1401.4459
An uncertainty principle for star formation. I. why galactic star formation relations break down below a certain spatial scale
Kruijssen, Longmore

Galactic scaling relations between the (surface densities of) the gas mass and the SFR are known to develop substantial scatter or even change form when considered below a certain spatial scale.  Quantify how this behavior should be expected due to the incomplete statistical sampling of independent SF regions.  Other included limiting factors are the incomplete sampling of SF tracers from the stellar IMF and the spatial drift between gas and stars.  Present a simple uncertainty principle for SF, which can be used to predict and interpret the failure of galactic SF relations on small spatial scales.  This uncertainty principle explains how the scatter of SF relations depends on the spatial scale and predicts a scale-dependent bias of the gas depletion time-scale when centering an aperture on gas or SF tracer peaks.  Show how the scatter and bias are sensitive to the physical size and time-scales involved in the SF process (such as its duration or the molecular cloud lifetime), and illustrate how the formalism provides a powerful tool to constrain these largely unknown quantities.  Thanks to its general form, the uncertainty principle can also be applied to other astrophysical systems, e.g. addressing the time-evolution of SF cores, protoplanetary discs, or galaxies and their nuclei.

1401.4503
Tracing the cosmic growth of super massive black holes to z~3 with Herschel
Delvecchio et al

Study a sample of Herschel-PACS selected galaxies within the GOODS-S and COSMOS fields in the framework of the PACS Evolutionary Probe (PEP) project.  Starting from the rich multi-wavelength photometric data-sets available in both fields, perform a broad-band SED decomposition to disentangle the possible AGN contribution from that related to the host galaxy.  Find that 37% of the sample shows signatures of nuclear activity at the 99% CL.  The probability to reveal AGN activity increases for bright SF galaxies (>1e11 Lsun) at z0.3, becoming about 80% for the brightest (>1e12Lsun) IR galaxies at z>=1.  Reconstruct the AGN bolometric LF and the SMBH growth rate across cosmic time up to z~3 from a FIR perspective.  This work shows general agreement with most of the panchromatic estimates from the literature, with the global BH growth peaking at z~2 and reproducing the observed local BH mass density with consistent values of the radiative efficiency e_rad(~0.07).