Multi-Wavelength Extragalactic Surveys: Star Formation of IR-Submm Selected Galaxies

This Thesis aims to identify and analyse galaxy populations over a range of redshifts in order to evaluate the star formation history over cosmic time. Explicitly focusing on the infrared to submillimetre regime, I carried out a comprehensive multi-wavelength approach at the North and South Ecliptic Poles (NEP/SEP). I explore four different methods to select high-z galaxies identifying a new sample of Dusty Star-Forming Galaxies (DSFGs) producing a legacy catalogue for future spectroscopic studies. These sources are modelled using contemporary spectral fitting algorithms. A detailed comparison of these algorithms concludes that the best results are obtained with the CIGALE package, deriving photometric redshifts and other physical properties. The star formation rate and stellar mass were derived defining their position on the Main Sequence of Galaxies finding a population of DSFGs lying above the MS with high star-formation efficiencies and extreme star-formation possibly due to mergers at early times. A lower redshift counterpart population at radio wavelengths was studied via radio-optical identification and multiwavelength data, calculating photometric redshifts providing better results than simply cross-matching the catalogue with heterogeneous ancillary redshift data. This sub-milliJansky population is then classified by infrared luminosity finding that the stellar mass and gas mass are one order of magnitude higher in more luminous galaxies than in less luminous galaxies. This population is segregated into AGN and DSFGs using a new infrared colour-colour diagrams concluding that using AKARI bands results in better AGN selection than that from WISE. Optical data at the SEP is reduced creating a new catalogue filling a vital gap in the multiwavelength data in this field. This new catalogue is combined with Spitzer and Herschel data identifying a population of Dust Obscured Galaxies at z∼2 the peak of the cosmic star-formation history

The AGN population in the AKARI NEP Deep Field

The AKARI North Ecliptic Pole Deep Field is a natural location to accomplish deep extragalactic surveys. It is supported by comprehensive ancillary data extending from radio to X-ray wavelengths, which have been used to classify radio sources as radio-loud and radio-quiet objects and to create a catalogue of Active Galactic Nuclei (AGN). This has been achieved by using a radio-optical classification and colour-colour diagrams rather than the more usual way based on spectroscopy Furthermore, we explore whether this technique can be extended by using a far-Infrared (FIR) colour-colour diagram which has been used to identify 268 high redshift candidates

The Radio-far Infrared Correlation in the NEP Deep Field

We report the results of a multi-wavelength study in the North Ecliptic Pole (NEP) deep field and examine the far infrared-radio correlation (FIRC) for high and low redshift objects. We have found a correlation between the GMRT data at 610 MHz and the Herschel data at 250µm that has been used to define a spectral index. This spectral index shows no evolution against redshift. As a result of the study, we show a radio colour-infrared diagram that can be used as a redshift indicator

Radio identifications in the NEP Deep Field

We have imaged the AKARI Deep Field with the GMRT radio telescope at 610 MHz, detecting 1224 radio components, which are optically identified with 455 optical galaxies having a mean r' magnitude brighter of 22.5 (to a completeness limit of 25.4 mag), and an average redshift ∼ 0.8

PANORAMIC - A Pure Parallel Wide Area Legacy Imaging Survey at 1-5 Micron

Where HST has characterized the UV universe to z=6-7 and beyond, JWST is designed to take the crucial next step and characterize the UV universe to z=12-15 (a factor of 2 in expansion rate), at only ~300 Myr after the Big Bang where we expect the first galaxies to form. Additionally, JWST for the first time allows studies of the restframe optical emission to z=10, a huge leap from the current z=3 (HST). To fully capitalize on JWST's unparalleled imaging AND spectroscopic capabilities, it is critical, however, to find the most precious intrinsically luminous candidate galaxies early in the mission. Large area imaging is thus needed from day one. Here, we propose to exploit the unique opportunity offered by pure parallel observing to efficiently obtain such a wide-area reference survey over 0.4 sq degrees in 6 NIRCam filters. By probing 7x larger area than any other currently planned (GTO/ERS) program our survey will probe a unique discovery space with unprecedented imaging at 1-5micron. These data overcome two major outstanding limitations in our current extragalactic census using yet-undiscovered populations: (1) the brightest and most distant sources that ended the cosmic Dark Ages at z>9 and (2) red sources at

Characteristics of mid-infrared PAH emission from star-forming galaxies selected at 250 μm in the North Ecliptic Pole field

Evolutionary properties of infrared (IR) luminous galaxies are important keys to understand dust-obscured star formation history and galaxy evolution. Based on near- to mid-IR imaging with nine continuous filters of the AKARI space telescope, we present the characteristics of dusty star-forming (SF) galaxies showing polycyclic aromatic hydrocarbon (PAH) features observed by the North Ecliptic Pole (NEP) wide field survey of AKARI and Herschel. All the sample galaxies from the AKARI/NEP-Wide data are selected based both on the Herschel/SPIRE 250 μm detection and optical spectroscopic redshift data. The physical modeling of spectral energy distribution (SED) using all available data points from u* to sub-mm 500 μm band, including WISE and PACS data where available, takes unique advantages of the continuous near- to mid-IR coverage, the reliable constraint on the far-IR peak, and spectroscopically determined accurate redshifts, as well as the energy balance principle by MAGPHYS. This enables us to derive physically meaningful and accurate total infrared luminosity and 8 μm (or PAH) luminosity consistently. Our sample galaxies are in the redshift range z < 1, and the majority of them appear to be normal SF/spiral populations showing PAH features near 8 μm. These SF galaxies showing PAHs in the mid-IR include various types, from quiescent to starbursts. Some of our sample show shortage of 8 μm luminosity compared to the total IR luminosity and this PAH deficit gets severe in more-luminous IR galaxies, suggesting PAH molecules in these galaxies are destroyed by a strong radiation field from the SF region or a large amount of cold dust in the interstellar medium. The specific SFR of our sample shows mass-dependent time evolution which is consistent with a downsizing evolutionary pattern

Torus Constraints in ANEPD-CXO245: A Compton-thick AGN with Double-peaked Narrow Lines

We report on the torus constraints of the Compton-thick active galactic nucleus (AGN) with double-peaked optical narrow-line region emission lines, ANEPD-CXO245, at z = 0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2–24 μm with the AKARI Infrared Camera, and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width (σ), and viewing angle (i). We analyze the X-ray spectrum as well as the UV–optical–infrared spectral energy distribution (UOI-SED) with clumpy torus models in X-ray (XCLUMPY) and infrared (CLUMPY), respectively. From our current data, the constraints on σ–i from both X-rays and UOI show that the line of sight crosses the torus as expected for a type 2 AGN. We obtain a small X-ray scattering fraction (NH from the X-ray spectrum, we find that the gas-to-dust ratio is <4 times larger than the Galactic value