Radio infrared correlation for galaxies: from today's instruments to SKA
Agata P¦piak1
T.T. Takeuchi2, A. Pollo1,3, A. Solarz2, and AKARI team
1Astronomical Observatory of the Jagiellonian University, Krakow, Poland 2Department of Particle and Astrophysical Science, Nagoya University, Japan 3National Centre for Nuclear Research, Warszawa, Poland
05.06.2013
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 1 / 25 Introduction
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 2 / 25 Radio infrared correlation Introduction
Far-infrared - radio correlation (FRC)
The radio and far-infrared (FIR) luminosities of galaxies are linearly correlated. The far-infrared - radio correlation (FRC) is one of the tightest and most universal empirical correlations known among global parameters of the observed galaxies. It spans over a wide range of galaxy types and seems to be valid both for local and distant Universe.
DSS images of NGC 1566, NGC 2559, NGC 891, NGC 1637.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 3 / 25 Radio infrared correlation Introduction
The correlation between IR and radio emission in Seyfert galaxies and star-forming galaxies in the local Universe was rst observed by van der Kruit (1971, 1973).
Source: van der Kruit (1971).
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 4 / 25 Radio infrared correlation Introduction
Presently FIR-radio correlation is believed to be driven mostly by star formation.
Starburst activity in the central region of nearby dwarf galaxy NGC 1569 (Arp 210). Taken by Hubble Space
Telescope.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 5 / 25 Radio infrared correlation Introduction
The correlation as a result of recent massive star formation - scenario:
Light emitted in UV and optical wavelengths by young masive stars heats the surrounding dust. Then dust reradiates energy at infrared wavelengths. (IR emission - thermal.)
Massive stars evolve to supernovae. Supernovae remnants accelerate cosmic ray electrons, which travel through interstellar magnetic eld and produce synchrotron radio emission. (Most of radio emission - non-thermal.)
The IR and radio emission mechanisms involve very dierent physical processes and timescales. The origin and physics of the FRC remains still under debate. Moreover, the correlation is also observed for AGN-bearing galaxies. It is still to be established if it is related only to star formation activity, or maybe some other processes are involved...
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 6 / 25 FRC for AKARI nearby galaxies
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 7 / 25 Radio infrared correlation Example: FRC for AKARI galaxies
Far-infrared data: AKARI FIS WIDE S band (90µm) (AKARI FIS All-Sky Survey Bright Source Catalogue) Radio data: NRAO VLA Sky Survey (NVSS): 1.4 GHz (with 45 FWHM resolution)
DSS and NVSS images of galaxies from AKARI All Sky Survey.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 8 / 25 Radio infrared correlation Example: FRC for AKARI galaxies
SAMPLE I: FIR selected galaxies
number of sources FIS catalogue 427071 MJy Galactic extinction I100µm < 10 sr 39930 Sources with NVSS radio uxes available 19248 Galaxies with redshift information available 13430 Galaxies with AGN activity 1230 Galaxies with no known AGN activity ('normal galaxies') 12200
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 9 / 25 Radio infrared correlation Example: FRC for AKARI galaxies
SAMPLE II: FIR and MIR selected galaxies number of sources IRC catalogue 870973 FIS catalogue 427071 IRC-FIS cross-correlation 50809 MJy Galactic extinction I100µm < 10 sr 3093 Galaxies 1546 Galaxies whose positions are available for NVSS (δ > −40o) 1246 Galaxies with measurable radio ux density (>3σ) on NVSS images* 1128 Galaxies with AGN activity* 301 Galaxies with no known
AGN activity ('normal galaxies')* 827
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 10 / 25 ∗ -with redshift information available Radio infrared correlation Example: FRC for AKARI galaxies
SAMPLE I: < z >= 0.040 zmedian = 0.030 SAMPLE II: < z >= 0.026 zmedian = 0.020
The most important part of redshifts histograms for SAMPLE I (left) and SAMPLE II (right).
The sample consists of galaxies mainly from local Universe.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 11 / 25 Radio infrared correlation Example: FRC for AKARI galaxies
Radio luminosity density vs. FIR luminosity for AKARI nearby galaxies for SAMPLE I (left) and SAMPLE II (right).
Green crosses represent galaxies with AGN activity, red crosses represent galaxies with no known AGN activity
('normal galaxies'). Note dierent scale on both plots.
FRC for AKARI galaxies
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 12 / 25 Radio infrared correlation Example: FRC for AKARI galaxies
S q log 90µm index as a function of redshift for SAMPLE I (left) and SAMPLE II (right). = S 1.4GHz Green crosses represent galaxies with AGN activity, red crosses represent galaxies with no known AGN activity ('normal galaxies').
Note dierent scale on both plots.
No evolution of q parameter with redshift in the considered redshift range.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 13 / 25 Radio-Infrared correlation for AKARI galaxies Example: FRC for AKARI galaxies
SAMPLE I Mean Median Dispersion The whole sample < q >= 2.18 2.21 0.26 Galaxies with AGN activity < qAGN >= 2.02 2.13 0.46 Normal galaxies < qn >= 2.20 2.22 0.23
SAMPLE II Mean Median Dispersion The whole sample < q >= 2.23 2.25 0.44 Galaxies with AGN activity < qAGN >= 2.04 2.18 0.65 Normal galaxies < qn >= 2.30 2.27 0.31
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 14 / 25 Radio infrared correlation Example: FRC for AKARI galaxies: motivation
Why is it worth to examine FRC for nearby AKARI galaxies?
AKARI provides the rst after IRAS all-sky survey of the sky in FIR wavelengths and gives a possibility of collecting statistically signi cant sample of galaxies and examining FRC of local galaxies in more details with signi cantly better resolution and sensitivity. Hence, we are able to determine the parameters of the correlation with better accuracy.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 15 / 25 FRC and SKA
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 16 / 25 Radio infrared correlation Perspectives: SKA
Just like in case of IR data, we need more accurate radio data. Since the Square Kilometre Array will be the world's largest and most sensitive radio telescope, it can help to answer many questions related to radio infrared correlation.
Source: http://www.skatelescope.org/.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 17 / 25 Radio infrared correlation with SKA 1. The spatially resolved studies within galaxies
Studies of FRC: possible not only in terms of global parameters (IR and radio luminosities) but also on dierent scales within galaxies An example: Tabatabaei et al. 2012: The SED of Galaxies, Proceedings of the IAU, IAU Symposium, Volume 284, p. 400-403
Source: Tabatabaei et al. 2012
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 18 / 25 Radio infrared correlation with SKA 1. The spatially resolved studies within galaxies
Source: Tabatabaei et al. 2012
The scale dependence of the synchrotron-FIR correlation can be explained by the turbulent-to-ordered magnetic eld ratio (=diusion length of CRe−) => FRC depends on properties of the magnetic eld in galaxies.
SKA with its resolution and sensitivity: very useful tool => WE NEED SKA!
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 19 / 25 Radio infrared correlation with SKA 2. The picture of FRC at low radio frequencies
So far, both spatially resolved and global observational studies of the FRC has been done primarily for radio emission at 1.4 GHz and higher frequencies.
Scarce low radio frequencies examination:
at global scales Cox et al., 1988, MNRAS 235, 1227; 150 MHz spatially resolved studies at ≈ 1 kpc scales Basu et al., 2012, ApJ, accepted to be published; 333 MHz
The reason: no required observational tools! => WE NEED SKA!
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 20 / 25 Radio infrared correlation with SKA 2. The picture of FRC at low radio frequencies
Why is the low radio frequencies examination so important for understanding FRC for galaxies? Answer: for that regime galaxies' emission is largely non-thermal (the thermal component is very low). Hence, this fact gives a chance for more detailed exhibition of the relation between the magnetic eld and star formation processes in galaxies! To identify the correct scenario we need observation at low frequencies for statistically signi cant sample of galaxies => WE NEED SKA
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 21 / 25 Radio infrared correlation with SKA 3. The evolution of FRC with z
The deep radio continuum surveys which may become possible using SKA: a possibility of studying the evolution of FRC with redshift
A predictive analysis for the behaviour of the FRC as a function of redshift (Murphy, E.J.; The Astrophysical Journal, Volume 706, Issue 1, pp. 482-496; 2009) shows that evolution in the FRC should occur with infrared/radio ratios increasing with redshift.
SKA can give a chance to characterize the high-z star formation history of the universe. => WE NEED SKA
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 22 / 25 Radio infrared correlation with SKA 3. The evolution of FRC with z
Source: Murphy 2009.
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 23 / 25 Radio infrared correlation with SKA Summary
SKA perspectives for answering the questions about radio infrared correlation:
What are the mechanisms responsible for the origin of radio infrared correlation?
Does radio infrared correlation hold for low radio frequencies and what are its parameters?
To what extend does the correlation hold in small scales within galaxies and what does it tell us about the properties of galaxies?
How does the radio infrared correlation evolve with dierent cosmic epochs?
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 24 / 25 Thank you for your attention
Agata P¦piak (OAUJ) FRC for galaxies 05.06.2013 25 / 25