We present the North Ecliptic Pole (NEP) Surveys with Infrared Camera (IRC) onboard the AKARI inf... more We present the North Ecliptic Pole (NEP) Surveys with Infrared Camera (IRC) onboard the AKARI infrared satellite. Two NEP surveys were designed: NEP-Deep was deep and NEP-Wide was wide, but shallow. One of the unique characteristics of IRC is nine broad-band filters which cover the continuous wavelength from 2 to 26 mum and all IRC filters were used for both
Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-ban... more Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-band large-area surveys around the ecliptic poles. The north ecliptic pole (NEP) is the best region for AKARI which has a sun-synchronous orbit that allows it conduct legacy surveys with all AKARI bands, i.e. nine bands in 2 -- 24 mum and 4 bands in 65 -- 160
The observation of the north ecliptic pole (NEP) region was carried out over nine photometric nig... more The observation of the north ecliptic pole (NEP) region was carried out over nine photometric nights between 2004 August 22 and September 22 using the 3.6m CFHT telescope located at Mauna Kea, Hawaii. The u* g' r' i' z' filter system provided with MegaCam is basically the same as that used by the Sloan Digital Sky Survey (SDSS; York et
We present the status of the AKARI Mission Program on the evolution of cluster of galaxies, CLEVL... more We present the status of the AKARI Mission Program on the evolution of cluster of galaxies, CLEVL. In order to understand the evolution of galaxies in cluster environment, we have conducted an AKARI imaging survey of galaxy clusters over a wide redshift range. For 8 low redshift clusters (z < 0.3), we performed 2-24 micron imaging in 6 passbands. For
We have conducted the largest extragalactic survey with IRC pointed observations, towards the nor... more We have conducted the largest extragalactic survey with IRC pointed observations, towards the north ecliptic pole (NEP). Using this survey, which covers 0.38 deg2, we demonstrate that IRC all-band photometry at 2-24 mum is capable of tracing the steep rise of flux at the blue side of PAH 6.2 mum feature. Single mid-infrared colors, such as S11-S7 and L15-S9W, can
Here we use the multi-wavelength data set of the AKARI NEP-deep survey, described in detail in Wa... more Here we use the multi-wavelength data set of the AKARI NEP-deep survey, described in detail in Wada et al. (2008PASJ...60S.517W). (1 data file).
We describe observational characteristics of three Extremely Red MIR-bright Objects (ERMOs, satis... more We describe observational characteristics of three Extremely Red MIR-bright Objects (ERMOs, satisfying R - [15] >= 6.5 AB mag) found in the AKARI North Ecliptic Pole (NEP) deep field at z=1.5-2.2, showing broad Mg II emission (˜5000 km sec-1) while their broad-band spectral energy distributions (SEDs) at optical and mid-infrared are power-law, similar to that of the type-2 AGN. Since
We describe the AKARI InfraRed Camera (IRC) imaging observation of early-type galaxies (ETGs) in ... more We describe the AKARI InfraRed Camera (IRC) imaging observation of early-type galaxies (ETGs) in A2218 at z ≅ 0.175. With the imaging capability at 11 and 15 mum, we investigate mid-infrared (MIR) properties of ETGs in the cluster environment. Among our flux-limited sample of 22 optical red sequence ETGs, we find that more than 50% have MIR-excess emission, and the
ABSTRACT The radio observations presented in this paper were observed during 2004 with the WSRT o... more ABSTRACT The radio observations presented in this paper were observed during 2004 with the WSRT operated at 20cm wavelength. (1 data file).
We present multi-band results for GRB071010B based on \Swift, \Suzaku, and ground-based optical o... more We present multi-band results for GRB071010B based on \Swift, \Suzaku, and ground-based optical observations. This burst is an ideal target to evaluate the robustness of the ${\rm E^{src}_{peak}-E_{iso}}$ and ${\rm E^{src}_{peak}-E_{\gamma}}$ relations, whose studies have been in stagnation due to the lack of the combined estimation of $\rm E^{src}_{peak}$ and long term optical monitoring. The joint prompt spectral fitting using
ABSTRACT Using a stellar mass limited sample of $\sim 46,600$ galaxies ($M_* &gt; 10^{9.1}\,M... more ABSTRACT Using a stellar mass limited sample of $\sim 46,600$ galaxies ($M_* &gt; 10^{9.1}\,M_{\odot}$) at $0.5 &lt; z &lt; 2$, we show that the tellar mass, rather than the environment, is the main parameter controlling quenching of star formation in galaxies with $M_* &gt; 10^{10}\,M_{\odot}$ out to $z=2$. On the other hand, the environmental quenching becomes efficient at $z &lt; 1$ regardless of galaxy mass, and it serves as a main star formation quenching mechanism for lower mass galaxies. Our result is based on deep optical and near-infrared imaging data over 2800 arcmin$^2$, enabling us to negate cosmic variance and identify 46 galaxy cluster candidates with $M \sim 10^{14}\,M_{\odot}$. From $M_* \sim 10^{9.5}$ to $10^{10.5}\,M_{\odot}$, the fraction of quiescent galaxies increases by a factor of $\sim 10$ over the entire redshift range, but the difference between cluster and field environment is negligible. Rapid evolution in the quiescent fraction is seen from $z=2$ to $z=1.3$ for massive galaxies suggesting a build-up of massive quiescent galaxies at $z &gt; 1.3$. For galaxies with $M_* &lt; 10^{10}\,M_{\odot}$ at $z &lt; 1.0$, the quiescent fraction is found to be as much as a factor of 2 larger in clusters than in field, showing the importance of environmental quenching in low mass galaxies at low redshift. Most high mass galaxies are already quenched at $z &gt; 1$, therefore environmental quenching does not play a significant role for them, although the environmental quenching efficiency is nearly identical between high and low mass galaxies.
There is a huge gap between properties of red-sequence selected massive galaxy clusters at z <... more There is a huge gap between properties of red-sequence selected massive galaxy clusters at z < 1 and Lyman-break selected proto-clusters at z> 3. It is important to understand when and how the z> 3 proto-clusters evolve into passive clusters at z < 1. We aim to fill this cluster desert by using the space-based N4(4µm) imaging with the AKARI. The z ′ −N4 color is a powerful separator of cluster galaxies at z> 1, taking advantage of the 4000˚A break and the 1.6µm bump. We carefully selected 16 promising cluster candidates at 0.9 < z < 1.7, which all show obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S15µm/S9µm flux ratio is an extinction-free indicator of galaxy star formation activity due to the redshifted PAH emission lines (6.2,7.7 and 8.6µm). We show statistically that the cluster galaxies have a lower S15µm/S9µm flux ratio than field galaxies, i.e., cluster galaxies already have lower star-formation ac...
We present the North Ecliptic Pole (NEP) Surveys with Infrared Camera (IRC) onboard the AKARI inf... more We present the North Ecliptic Pole (NEP) Surveys with Infrared Camera (IRC) onboard the AKARI infrared satellite. Two NEP surveys were designed: NEP-Deep was deep and NEP-Wide was wide, but shallow. One of the unique characteristics of IRC is nine broad-band filters which cover the continuous wavelength from 2 to 26 mum and all IRC filters were used for both
Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-ban... more Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-band large-area surveys around the ecliptic poles. The north ecliptic pole (NEP) is the best region for AKARI which has a sun-synchronous orbit that allows it conduct legacy surveys with all AKARI bands, i.e. nine bands in 2 -- 24 mum and 4 bands in 65 -- 160
The observation of the north ecliptic pole (NEP) region was carried out over nine photometric nig... more The observation of the north ecliptic pole (NEP) region was carried out over nine photometric nights between 2004 August 22 and September 22 using the 3.6m CFHT telescope located at Mauna Kea, Hawaii. The u* g' r' i' z' filter system provided with MegaCam is basically the same as that used by the Sloan Digital Sky Survey (SDSS; York et
We present the status of the AKARI Mission Program on the evolution of cluster of galaxies, CLEVL... more We present the status of the AKARI Mission Program on the evolution of cluster of galaxies, CLEVL. In order to understand the evolution of galaxies in cluster environment, we have conducted an AKARI imaging survey of galaxy clusters over a wide redshift range. For 8 low redshift clusters (z < 0.3), we performed 2-24 micron imaging in 6 passbands. For
We have conducted the largest extragalactic survey with IRC pointed observations, towards the nor... more We have conducted the largest extragalactic survey with IRC pointed observations, towards the north ecliptic pole (NEP). Using this survey, which covers 0.38 deg2, we demonstrate that IRC all-band photometry at 2-24 mum is capable of tracing the steep rise of flux at the blue side of PAH 6.2 mum feature. Single mid-infrared colors, such as S11-S7 and L15-S9W, can
Here we use the multi-wavelength data set of the AKARI NEP-deep survey, described in detail in Wa... more Here we use the multi-wavelength data set of the AKARI NEP-deep survey, described in detail in Wada et al. (2008PASJ...60S.517W). (1 data file).
We describe observational characteristics of three Extremely Red MIR-bright Objects (ERMOs, satis... more We describe observational characteristics of three Extremely Red MIR-bright Objects (ERMOs, satisfying R - [15] >= 6.5 AB mag) found in the AKARI North Ecliptic Pole (NEP) deep field at z=1.5-2.2, showing broad Mg II emission (˜5000 km sec-1) while their broad-band spectral energy distributions (SEDs) at optical and mid-infrared are power-law, similar to that of the type-2 AGN. Since
We describe the AKARI InfraRed Camera (IRC) imaging observation of early-type galaxies (ETGs) in ... more We describe the AKARI InfraRed Camera (IRC) imaging observation of early-type galaxies (ETGs) in A2218 at z ≅ 0.175. With the imaging capability at 11 and 15 mum, we investigate mid-infrared (MIR) properties of ETGs in the cluster environment. Among our flux-limited sample of 22 optical red sequence ETGs, we find that more than 50% have MIR-excess emission, and the
ABSTRACT The radio observations presented in this paper were observed during 2004 with the WSRT o... more ABSTRACT The radio observations presented in this paper were observed during 2004 with the WSRT operated at 20cm wavelength. (1 data file).
We present multi-band results for GRB071010B based on \Swift, \Suzaku, and ground-based optical o... more We present multi-band results for GRB071010B based on \Swift, \Suzaku, and ground-based optical observations. This burst is an ideal target to evaluate the robustness of the ${\rm E^{src}_{peak}-E_{iso}}$ and ${\rm E^{src}_{peak}-E_{\gamma}}$ relations, whose studies have been in stagnation due to the lack of the combined estimation of $\rm E^{src}_{peak}$ and long term optical monitoring. The joint prompt spectral fitting using
ABSTRACT Using a stellar mass limited sample of $\sim 46,600$ galaxies ($M_* &gt; 10^{9.1}\,M... more ABSTRACT Using a stellar mass limited sample of $\sim 46,600$ galaxies ($M_* &gt; 10^{9.1}\,M_{\odot}$) at $0.5 &lt; z &lt; 2$, we show that the tellar mass, rather than the environment, is the main parameter controlling quenching of star formation in galaxies with $M_* &gt; 10^{10}\,M_{\odot}$ out to $z=2$. On the other hand, the environmental quenching becomes efficient at $z &lt; 1$ regardless of galaxy mass, and it serves as a main star formation quenching mechanism for lower mass galaxies. Our result is based on deep optical and near-infrared imaging data over 2800 arcmin$^2$, enabling us to negate cosmic variance and identify 46 galaxy cluster candidates with $M \sim 10^{14}\,M_{\odot}$. From $M_* \sim 10^{9.5}$ to $10^{10.5}\,M_{\odot}$, the fraction of quiescent galaxies increases by a factor of $\sim 10$ over the entire redshift range, but the difference between cluster and field environment is negligible. Rapid evolution in the quiescent fraction is seen from $z=2$ to $z=1.3$ for massive galaxies suggesting a build-up of massive quiescent galaxies at $z &gt; 1.3$. For galaxies with $M_* &lt; 10^{10}\,M_{\odot}$ at $z &lt; 1.0$, the quiescent fraction is found to be as much as a factor of 2 larger in clusters than in field, showing the importance of environmental quenching in low mass galaxies at low redshift. Most high mass galaxies are already quenched at $z &gt; 1$, therefore environmental quenching does not play a significant role for them, although the environmental quenching efficiency is nearly identical between high and low mass galaxies.
There is a huge gap between properties of red-sequence selected massive galaxy clusters at z <... more There is a huge gap between properties of red-sequence selected massive galaxy clusters at z < 1 and Lyman-break selected proto-clusters at z> 3. It is important to understand when and how the z> 3 proto-clusters evolve into passive clusters at z < 1. We aim to fill this cluster desert by using the space-based N4(4µm) imaging with the AKARI. The z ′ −N4 color is a powerful separator of cluster galaxies at z> 1, taking advantage of the 4000˚A break and the 1.6µm bump. We carefully selected 16 promising cluster candidates at 0.9 < z < 1.7, which all show obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S15µm/S9µm flux ratio is an extinction-free indicator of galaxy star formation activity due to the redshifted PAH emission lines (6.2,7.7 and 8.6µm). We show statistically that the cluster galaxies have a lower S15µm/S9µm flux ratio than field galaxies, i.e., cluster galaxies already have lower star-formation ac...
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