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Deep MIR surveys have revealed numerous strongly star-forming galaxies at redshift z~<2. Their MIR fluxes are produced by a combination of continuum and PAH emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy. We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR up to z~=0.5, by paying particular attention to their PAH properties. We conducted a low-resolution (R~=50) slitless spectroscopic survey at 5-13um of 9um flux-selected sources (>0.3 mJy) around the North Ecliptic Pole with the Infrared Camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identified 48 PAH galaxies with PAH 6.2, 7.7, and 8.6um features at z<0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and AKARI/IRC imaging covering 0.37-18um were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7um PAH feature over the 3.5um stellar component of the SEDs. The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7um bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identified a PAH-enhanced population at z~>0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we could not confirm this optically thick component from our spectral analysis., Comment: 61 pages, 24 figures, accepted for publication in Astronomy and Astrophysics

We aim to study star-forming galaxies by using a blind spectroscopic survey at mid-infrared (MIR) wavelengths to understand evolution of their star formation rate (SFR) and specific SFR (SFR per stellar mass) up to z in the order of 0.5, by paying particular attention to their Polycyclic Aromatic Hydrocarbon (PAH) properties. We conducted a low-resolution (R approximately equal to 50) slitless spectroscopic survey at 5-13 micrometers of 9 micrometers flux-selected sources (approximately greater than 0.3 mJy) around the North Ecliptic Pole with the Infrared Camera (IRC) onboard AKARI. We identified 48 PAH galaxies with PAH 6.2, 7.7, and 8.6 micrometers features at z approximately less than 0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and AKARI/IRC imaging are produced and analyzed in conjunction with the PAH spectroscopy. The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7 micrometers (PAH) bumps, except that the PAH enhancement (luminosity ratio of the 7.7 micrometers PAH feature over the 3.5 micrometers stellar bump) significantly varies as a function of the PAH luminosities. We identified a PAH-enhanced population at z approximately less than 0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a young and dusty starburst with a very old population can successfully reproduce most SED characteristics., Meeting Information: The 4th AKARI International Conference: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (October 17-20, 2017. The University of Tokyo), Bunkyo-ku, Tokyo, Japan, Number of authors: 27, Physical characteristics: Original contains color illustrations, 会議情報: 第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京, 著者人数: 27名, 形態: カラー図版あり

Multi-wavelength data from the far-UV to the far-IR have been collected in the North Ecliptic Pole (NEP). These data are crucial to understand the galaxy populations detected in this study. More specifically, this work made use of GALEX data in far- and near-UV, SUBARU HSC data in the optical, AKARI and WISE data in the near- and mid-IR and Herschel data in the far-IR to try and identify a sample of candidate high-redshift, possibly lensed galaxies. From the list of candidates, we have obtained follow-up observations at IRAM/30m, NOEMA, Gemini North and SMA to better understand our galaxies. This work is the beginning of a promising project dedicated to the study of high-redshift galaxies in the NEP., Meeting Information: The 4th AKARI International Conference: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (October 17-20, 2017. The University of Tokyo), Bunkyo-ku, Tokyo, Japan, Physical characteristics: Original contains color illustrations, 会議情報: 第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京, 形態: カラー図版あり

Deep MIR surveys have revealed numerous strongly star-forming galaxies at redshift z~<2. Their MIR fluxes are produced by a combination of continuum and PAH emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy. We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR up to z~=0.5, by paying particular attention to their PAH properties. We conducted a low-resolution (R~=50) slitless spectroscopic survey at 5-13um of 9um flux-selected sources (>0.3 mJy) around the North Ecliptic Pole with the Infrared Camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identified 48 PAH galaxies with PAH 6.2, 7.7, and 8.6um features at z<0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and AKARI/IRC imaging covering 0.37-18um were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7um PAH feature over the 3.5um stellar component of the SEDs. The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7um bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identified a PAH-enhanced population at z~>0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we could not confirm this optically thick component from our spectral analysis., Comment: 61 pages, 24 figures, accepted for publication in Astronomy and Astrophysics

$\mathit{Herschel}$ extragalactic surveys offer a unique opportunity to efficiently select a significant number of rare and massive dusty objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. To search for $z\geq4$ dusty star-forming galaxies, in this work we consider red SPIRE objects with fluxes rising from 250 $\mu$m to $500\:\mu$m (so-called "500 $\mu$m-risers"). We aim to implement a novel method to obtain a statistical sample of "500 $\mu$m-risers" and fully evaluate our selection inspecting different models of galaxy evolution. We consider one of the largest and deepest ${\it Herschel}$ surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. We select 133 "500 $\mu$m-risers" over 55 deg$^{2}$, imposing the criteria: $S_{500}>S_{350}>S_{250}$, $S_{250}>13.2$ mJy and $S_{500}>$30 mJy. Differential number counts are in a fairly good agreement with models, displaying better match than other existing samples. In order to interpret the statistical properties of selected sources, which has been proven as a very challenging task due the complexity of observed artefacts, we make end-to-end simulations including physical clustering and lensing. The estimated fraction of strongly lensed sources is $24^{+6}_{-5}\%$ based on models. We present the faintest known statistical sample of "500 $\mu$m-risers" and show that noise and strong lensing have crucial impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at $44$ sources., Comment: 28 pages, 13 figures, version accepted for publication in A&A

$\mathit{Herschel}$ extragalactic surveys offer a unique opportunity to efficiently select a significant number of rare and massive dusty objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. To search for $z\geq4$ dusty star-forming galaxies, in this work we consider red SPIRE objects with fluxes rising from 250 $\mu$m to $500\:\mu$m (so-called "500 $\mu$m-risers"). We aim to implement a novel method to obtain a statistical sample of "500 $\mu$m-risers" and fully evaluate our selection inspecting different models of galaxy evolution. We consider one of the largest and deepest ${\it Herschel}$ surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. We select 133 "500 $\mu$m-risers" over 55 deg$^{2}$, imposing the criteria: $S_{500}>S_{350}>S_{250}$, $S_{250}>13.2$ mJy and $S_{500}>$30 mJy. Differential number counts are in a fairly good agreement with models, displaying better match than other existing samples. In order to interpret the statistical properties of selected sources, which has been proven as a very challenging task due the complexity of observed artefacts, we make end-to-end simulations including physical clustering and lensing. The estimated fraction of strongly lensed sources is $24^{+6}_{-5}\%$ based on models. We present the faintest known statistical sample of "500 $\mu$m-risers" and show that noise and strong lensing have crucial impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at $44$ sources., Comment: 28 pages, 13 figures, version accepted for publication in A&A