How much Microwave Emission can we See from Interplanetary Dust?

Valeri Dikarev

at the Cosmic Structure and Evolution Workshop

on September, 24, 2009 in Bielefeld

Why was interplanetary dust ignored?

• IPD is not on the list of biases for WMAP

Why does IPD’s emissivity drops?

• Standard emissivity law λ-2 for λ >> size

• IPD sizes from 10 to 100 μm

• Grün et al. (1985): the interplanetary meteoroid flux model

How do we know dust size distribution?

• In the size range above 100 μm: from Earth-bound measurements only!

Is interplanetary dust really ignorable?

• ‘Clouds’ are composed of macroscopic particles

A proper estimate of microwave emission should answer two questions

• How big should meteoroids be in order to stay hidden in the infrared light and mimic the CMB spectrum in the microwaves?

• How many such meteoroids are in the Solar system?

The optical constants

• Homogeneous silicate spheres

The optical constants

• Homogeneous carbonaceous spheres

The optical constants

• Homogeneous iron spheres

The absorption efficiencies

• Homogeneous silicate spheres

The absorption efficiencies

• Homogeneous carbonaceous spheres

The absorption efficiencies

• Homogeneous iron spheres

The excess temperature spectra

• Homogeneous silicate spheres, τIR=10-7

The excess temperature spectra

• Homogeneous carbonaceous spheres

How many big meteoroids are there?• The radial number density

distribution of 135 short-period comets, time-averaged

• The cumulative number of meteoroids from SP comets on the line of sight from the Earth in the anti-solar direction

• The optical depth of big (>100μm) meteoroids can reach 10-7 and match that of the ‘visible’ dust (from 10 to 100μm in size)

Summary

• Thermal emission from dust in the microwaves estimated as ~10 μK– Intriguingly close to anomaly magnitude (~30 μK)– Alarmingly higher than the currently presumed

systematic biases of WMAP data (5 μK)• Dust can be a low noise for the CMB studies• CMB (~100 μK) is a huge noise for the dust

studies

Results to appear in November’s ApJ