Radio infrared correlation for galaxies: from today's instruments to SKA

Transcription

1 Radio infrared correlation for galaxies: from today's instruments to SKA Agata P piak 1 T.T. Takeuchi 2, A. Pollo 1,3, A. Solarz 2, and AKARI team 1 Astronomical Observatory of the Jagiellonian University, Krakow, Poland 2 Department of Particle and Astrophysical Science, Nagoya University, Japan 3 National Centre for Nuclear Research, Warszawa, Poland Agata P piak (OAUJ) FRC for galaxies / 25

2 Introduction Agata P piak (OAUJ) FRC for galaxies / 25

3 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 Agata P piak (OAUJ) FRC for galaxies / 25

4 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 / 25

5 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 / 25

6 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 / 25

7 FRC for AKARI nearby galaxies Agata P piak (OAUJ) FRC for galaxies / 25

8 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 / 25

9 Radio infrared correlation Example: FRC for AKARI galaxies SAMPLE I: FIR selected galaxies number of sources FIS catalogue Galactic extinction I 100µm < 10 MJy sr Sources with NVSS radio uxes available Galaxies with redshift information available Galaxies with AGN activity 1230 Galaxies with no known AGN activity ('normal galaxies') Agata P piak (OAUJ) FRC for galaxies / 25

10 Radio infrared correlation Example: FRC for AKARI galaxies SAMPLE II: FIR and MIR selected galaxies number of sources IRC catalogue FIS catalogue IRC-FIS cross-correlation Galactic extinction I 100µm < 10 MJy sr 3093 Galaxies 1546 Galaxies whose positions are available for NVSS (δ > 40 o ) 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 / 25

11 Radio infrared correlation Example: FRC for AKARI galaxies SAMPLE I: < z >= z median = SAMPLE II: < z >= z median = 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 / 25

12 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 / 25

13 Radio infrared correlation Example: FRC for AKARI galaxies ( ) S 90µm q = log 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 / 25

14 Radio-Infrared correlation for AKARI galaxies Example: FRC for AKARI galaxies SAMPLE I Mean Median Dispersion The whole sample < q >= Galaxies with AGN activity < q AGN >= Normal galaxies < q n >= SAMPLE II Mean Median Dispersion The whole sample < q >= Galaxies with AGN activity < q AGN >= Normal galaxies < q n >= Agata P piak (OAUJ) FRC for galaxies / 25

15 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 signicant sample of galaxies and examining FRC of local galaxies in more details with signicantly 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 / 25

16 FRC and SKA Agata P piak (OAUJ) FRC for galaxies / 25

17 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: Agata P piak (OAUJ) FRC for galaxies / 25

18 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 Source: Tabatabaei et al Agata P piak (OAUJ) FRC for galaxies / 25

19 Radio infrared correlation with SKA 1. The spatially resolved studies within galaxies Source: Tabatabaei et al 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 / 25

20 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 / 25

21 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 signicant sample of galaxies => WE NEED SKA Agata P piak (OAUJ) FRC for galaxies / 25

22 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 ; 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 / 25

23 Radio infrared correlation with SKA 3. The evolution of FRC with z Source: Murphy Agata P piak (OAUJ) FRC for galaxies / 25

24 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 / 25

25 Thank you for your attention Agata P piak (OAUJ) FRC for galaxies / 25