The Calibration of Polycyclic Aromatic Hydrocarbon Dust Emission as a Star Formation Rate Indicator in the AKARI NEP Survey
Helen Kyung Kim, Matthew A. Malkan, Toshinobu Takagi, Nagisa Oi, Denis Burgarella, Takamitsu Miyaji, Hyunjin Shim, Hideo Matsuhara, Tomotsugu Goto, Yoichi Ohyam… 展开作者
Helen Kyung Kim, Matthew A. Malkan, Toshinobu Takagi, Nagisa Oi, Denis Burgarella, Takamitsu Miyaji, Hyunjin Shim, Hideo Matsuhara, Tomotsugu Goto, Yoichi Ohyama, Veronique Buat, Seong Jin Kim
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Accepted for publication in The Astrophysical Journal. 50 pages, 27 figures, 9 tables
Polycyclic aromatic hydrocarbon (PAH) dust emission has been proposed as an effective extinction-independent star formation rate (SFR) indicator in the mid-infrared (MIR), but this may depend on conditions in the interstellar medium. The coverage of the AKARI/Infrared Camera (IRC) allows us to study the effects of metallicity, starburst intensity, and active galactic nuclei on PAH emission in galaxies with $f_ν(L18W)\lesssim 19$ AB mag. Observations include follow-up, rest-frame optical spectra of 443 galaxies within the AKARI North Ecliptic Pole survey that have IRC detections from 7-24 $μ$m. We use optical emission line diagnostics to infer SFR based on H$α$ and [O II]$λλ3726,3729$ emission line luminosities. The PAH 6.2 $μ$m and PAH 7.7 $μ$m luminosities ($L(PAH\ 6.2\ μm)$ and $L(PAH\ 7.7\ μm)$, respectively) derived using multi-wavelength model fits are consistent with those derived from slitless spectroscopy within 0.2 dex. $L(PAH\ 6.2\ μm)$ and $L(PAH\ 7.7\ μm)$ correlate linearly with the 24 $μ$m-dust corrected H$α$ luminosity only for normal, star-forming ``main-sequence" galaxies. Assuming multi-linear correlations, we quantify the additional dependencies on metallicity and starburst intensity, which we use to correct our PAH SFR calibrations at $0<z<1.2$ for the first time. We derive the cosmic star formation rate density (SFRD) per comoving volume from $0.15 \lesssim z \lesssim 1$. The PAH SFRD is consistent with that of the far-infrared and reaches an order of magnitude higher than that of uncorrected UV observations at $z\sim1$. Starburst galaxies contribute $\gtrsim 0.7$ of the total SFRD at $z\sim1$ compared to main-sequence galaxies.
The infrared Astronomical Satellite AKARI conducted deep ($\sim$ 0.4 deg$^2$) and wide ($\sim 5.4$ deg$^2$) surveys around the North Ecliptic Pole (NEP) with its InfraRed Camera (IRC) with nine filters continuously covering the 2-25 $μ$m range. These photometric bands include three filters that fill the `Spitzer gap' between the wavelength coverages of IRAC and MIPS. This unique feature has enabled us to make sensitive mid-infrared detection of AGN candidates at z$\sim$ 1-2, based on the Spectral Energy Distribution (SED) fitting including hot dust emission in the AGN torus. This enables us to…
We study the environmental dependence of the strength of polycyclic aromatic hydrocarbon (PAH) emission by AKARI observations of RX J0152.7-1357, a galaxy cluster at z=0.84. PAH emission reflects the physical conditions of galaxies and dominates 8 um luminosity (L8), which can directly be measured with the L15 band of AKARI. L8 to infrared luminosity (LIR) ratio is used as a tracer of the PAH strength. Both photometric and spectroscopic redshifts are applied to identify the cluster members. The L15-band-detected galaxies tend to reside in the outskirt of the cluster and have optically green co…
We present a preliminary analysis of clustering of galaxies luminous in the near- and mid-infrared as seen by seven various ilters of the AKARI IRC instrument from 2 $μ$m to 24 $μ$m in the the AKARI NEP-Deep field. We compare populations of galaxies detected in different filters and their clustering properties. We conclude that different AKARI filters allow to trace different populations composed mainly of star-forming galaxies located in different environments. In particular, the mid-infrared filters at redshift z $\sim$ 0.8 and higher trace a population of strongly evolving galaxies located …
The north ecliptic pole (NEP) field is a natural deep field location for many satellite observations. It has been targeted manytimes since it was surveyed by the AKARI space telescope with its unique wavelength coverage from the near- to mid-infrared(mid-IR). Many follow-up observations have been carried out and made this field one of the most frequently observed areas witha variety of facilities, accumulating abundant panchromatic data from X-ray to radio wavelength range. Recently, a deep opticalsurvey with the Hyper Suprime-Cam (HSC) at the Subaru telescope covered the NEP-Wide (NEPW) field…
We study the galaxy merger fraction and its dependence on star formation mode in the5.4 square degrees of the North Ecliptic Pole-Wide field. We select 6352 galaxies withAKARI 9μm detections, and identify mergers among them using the Gini coefficientand M20derived from the Subaru/HSC optical images. We obtain the total infraredluminosity and star formation rate of galaxies using the spectral energy distributiontemplates based on one band, AKARI 9μm. We classify galaxies into three differentstar formation modes (i.e. starbursts, main sequence, and quiescent galaxies) andcalculate the merger fra…
In this research, we provide a new, efficient method to select infrared (IR) active galatic nucleus (AGN). In the past, AGN selection in IR had been established by many studies using color-color diagrams. However, those methods have a problem in common that the number of bands is limited. The AKARI North Ecliptic Pole (NEP) survey was carried out by the AKARI Infrared Camera (IRC), which has 9 filters in mid-IR with a continuous wavelength coverage from 2 to 24$μ$m$^{-1}$. Based on the intrinsic different mid-IR features of AGN and star-forming galaxies (SFGs), we performed SED fitting to sepa…
Revealing what fraction of galaxies harbor AGN is central in understanding black hole accretion history of the Universe. However, optical and soft X-ray surveys miss the most highly obscured AGNs. Infrared (IR), instead, is more robust against absorption. Previous IR photometric surveys, however, only had 4 or 5 filters in mid-IR. Our AKARI North Ecliptic Pole (NEP) wide field sample has 18 filters in mid-IR (9 from AKARI, 4 from WISE, and 5 from Spitzer), for the first time, allowing a sophisticated mid-IR SED fitting diagnosis for a statistical number of sources (89178 over 5.4 deg$^2$). By …
In this proceedings application of a fuzzy Support Vector Machine (FSVM) learning algorithm, to classify mid-infrared (MIR) sources from the AKARI NEP Deep field into three classes: stars, galaxies and AGNs, is presented. FSVM is an improved version of the classical SVM algorithm, incorporating measurement errors into the classification process; this is the first successful application of this algorithm in the astronomy. We created reliable catalogues of galaxies, stars and AGNs consisting of objects with MIR measurements, some of them with no optical counterparts. Some examples of identified …
Context. The North Ecliptic Pole (NEP) field provides a unique set of panchromatic data, well suited for active galactic nuclei (AGN) studies. Selection of AGN candidates is often based on mid-infrared (MIR) measurements. Such method, despite its effectiveness, strongly reduces a catalog volume due to the MIR detection condition. Modern machine learning techniques can solve this problem by finding similar selection criteria using only optical and near-infrared (NIR) data. Aims. Aims of this work were to create a reliable AGN candidates catalog from the NEP field using a combination of optical …
Understanding infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution. Japanese infrared satellite, AKARI, provided unique data sets to probe this both at low and high redshift; the AKARI all sky survey in 6 bands (9-160 $μ$m), and the AKARI NEP survey in 9 bands (2-24$μ$m). The AKARI performed all sky survey in 6 IR bands (9, 18, 65, 90, 140, and 160 $μ$m) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, we measure the total…
The anomalous microwave emission (AME) still lacks a conclusive explanation. This excess of emission, roughly between 10 and 50 GHz, correlates spatially with interstellar dust, prompting a "spinning dust" hypothesis: electric dipole emission by rapidly rotating, small dust grains. The typical peak frequency range of the AME profile implicates grains on the order of ~1 nm, suggesting polycyclic aromatic hydrocarbon molecules (PAHs). We compare AKARI/Infrared Camera (IRC), with its thorough PAH-band coverage, to AME intensity estimates from the Planck Collaboration, in the λ Orionis region. We …
Evolutionary properties of infrared (IR) luminous galaxies are important keys to understand dust-obscured star formation history and galaxy evolution. Based on the near- to mid-IR imaging with 9 continuous filters of AKARI space telescope, we present the characteristics of dusty star-forming (SF) galalxies 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 dat…
The $AKARI$ infrared (IR) space telescope conducted two surveys (Deep and Wide) in the North Ecliptic Pole (NEP) field to find more than 100,000 IR sources using its Infrared Camera (IRC). IRC's 9 filters, which cover wavebands from 2 to 24 $μ$m continuously, make $AKARI$ unique in comparison with other IR observatories such as $Spitzer$ or $WISE$. However, studies of the $AKARI$ NEP-Wide field sources had been limited due to the lack of follow-up observations in the ultraviolet (UV) and optical. In this work, we present the Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam $u$-band sour…
Much of the star formation is obscured by dust. For the complete understanding of the cosmic star formation history (CSFH), infrared (IR) census is indispensable. AKARI carried out deep mid-infrared observations using its continuous 9-band filters in the North Ecliptic Pole (NEP) field (5.4 deg$^2$). This took significant amount of satellite's lifetime, $\sim$10\% of the entire pointed observations. By combining archival Spitzer (5 bands) and WISE (4 bands) mid-IR photometry, we have, in total, 18 band mid-IR photometry, which is the most comprehensive photometric coverage in mid-IR for thousa…
The $AKARI$ space infrared telescope has performed near- to mid-infrared (MIR) observations on the North Ecliptic Pole Wide (NEPW) field (5.4 deg$^2$) for about one year. $AKARI$ took advantage of its continuous nine photometric bands, compared with NASA's $Spitzer$ and WISE space telescopes, which had only four filters with a wide gap in the MIR. The $AKARI$ NEPW field lacked deep and homogeneous optical data, limiting the use of nearly half of the IR sources for extra-galactic studies owing to the absence of photometric redshifts (photo-zs). To remedy this, we have recently obtained deep opt…
Galactic infrared (IR) bubbles, which have shell-like structures in the mid-IR wavelengths, are known to contain massive stars near their centers. IR bubbles in inner Galactic regions ($|$l$|\leq$ 65$^{\circ}$, $|$b$|\leq$ 1$^{\circ}$) have so far been studied well to understand the massive star formation mechanisms. In this study, we expand the research area to the whole Galactic plane (0$^{\circ}\leq$ l $<$360$^{\circ}$, $|$b$|\leq$ 5$^{\circ}$), using the AKARI all-sky survey data. We limit our study on large bubbles with angular radii of $>1'$ to reliably identify and characterize them. Fo…
Galaxy clusters provide an excellent probe in various research fields in astrophysics and cosmology. However, the number of galaxy clusters detected so far in the $AKARI$ North Ecliptic Pole (NEP) field is limited. In this work, we provide galaxy cluster candidates in the $AKARI$ NEP field with the minimum requisites based only on coordinates and photometric redshift (photo-$z$) of galaxies. We used galaxies detected in 5 optical bands ($g$, $r$, $i$, $z$, and $Y$) by the Subaru Hyper Suprime-Cam (HSC), assisted with $u$-band from Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam, and IR…
We present a large sample of 2.5-38 $μm$ galaxy spectra drawn from a cross-archival comparison in the AKARI-Spitzer Extragalactic Spectral Survey (ASESS), and investigate a subset of 113 star-forming galaxies with prominent polycyclic aromatic hydrocarbon (PAH) emission spanning a wide range of star formation properties. With AKARI's extended 2.5-5 $μm$ wavelength coverage, we self-consistently model for the first time all PAH emission bands using a modified version of PAHFIT. We find $L_\mathrm{PAH\,3.3}/L_\mathrm{IR}$ $\sim$ 0.1% and the 3.3 $μm$ PAH feature contributes $\sim$1.5-3% to the t…
We present AKARI 2.5-5um spectra of 145 local luminous infrared galaxies in the Great Observatories All-sky LIRG Survey. In all of the spectra, we measure the line fluxes and EQWs of the polycyclic aromatic hydrocarbon (PAH) at 3.3um and the hydrogen recombination line Br-alpha, with apertures matched to the slit sizes of the Spitzer spectrograph and with an aperture covering ~95% of the total flux in the AKARI 2D spectra. The star formation rates (SFRs) derived from Br-alpha measured in the latter aperture agree well with SFRs(LIR), when the dust extinction correction is adopted based on the …
We investigate the variation in the mid-infrared spectral energy distributions of 373 low-redshift ($z<0.4$) star-forming galaxies, which reflects a variety of polycyclic aromatic hydrocarbon (PAH) emission features. The relative strength of PAH emission is parameterized as $q_\mathrm{PAH}$, which is defined as the mass fraction of PAH particles in the total dust mass. With the aid of continuous mid-infrared photometric data points covering 7-24$μ$m and far-infrared flux densities, $q_\mathrm{PAH}$ values are derived through spectral energy distribution fitting. The correlation between $q_\mat…
Galactic infrared (IR) bubbles, which can be seen as shell-like structures at mid-IR wavelengths, are known to possess massive stars within their shell boundaries. In our previous study, Hanaoka et al. (2019) expanded the research area to the whole Galactic plane ($0^{\circ} \leq l \leq 360^{\circ}$, $|b| \leq 5^{\circ}$) and studied systematic differences in the shell morphology and the IR luminosity of the IR bubbles between inner and outer Galactic regions. In this study, utilizing high spatial-resolution data of AKARI and WISE in the mid-IR and Herschel in the far-IR, we investigate the sp…
We present the physical properties of AKARI sources without optical counterparts in optical images from the Hyper Suprime-Cam (HSC) on the Subaru telescope. Using the AKARI infrared (IR) source catalog and HSC optical catalog, we select 583 objects that do not have HSC counterparts in the AKARI North Ecliptic Pole (NEP) wide survey field ($\sim 5$ deg$^{2}$). Because the HSC limiting magnitude is deep ($g_{\rm AB}$ $\sim 28.6$), these are good candidates for extremely red star-forming galaxies (SFGs) and/or active galactic nuclei (AGNs), possibly at high redshifts. We compile multi-wavelength …
