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Red Star Forming Galaxies and Their Environment at z=0.4 Revealed by Panoramic H-alpha Imaging
Yusei Koyama,Tadayuki Kodama,Fumiaki Nakata,Kazuhiro Shimasaku,Sadanori Okamura
Physics , 2011, DOI: 10.1088/0004-637X/734/1/66
Abstract: We present a wide-field H-alpha imaging survey of the rich cluster CL0939+4713 (Abell 851) at z=0.41 with Suprime-Cam on the Subaru Telescope, using the narrow-band filter NB921. The survey is sensitive to active galaxies with star formation rates down to ~0.3Msun/yr throughout the 27'x27' field, and we identified 445 H-alpha emitters along the large-scale structures around the cluster. Using this sample, we find that (1) the fraction of H-alpha emitters is a strong function of environment and shows a clear decline toward the cluster central region. We also find that (2) the color of H-alpha emitters is clearly dependent on environment. The majority of the H-alpha emitters have blue colors with B-I<2, but we find H-alpha emitters with red colors as well. Such red emitters are very rare in the cluster center or its immediate surrounding regions, while they are most frequently found in groups located far away from the cluster center. These groups coincide with the environment where a sharp transition in galaxy color distribution is seen. This may suggest that dusty star formation activity tends to be involved in galaxy truncation processes that are effective in groups, and it is probably related to the "pre-processing" that generates present-day cluster S0 galaxies. Finally, we confirm that (3) the mass-normalized integrated star formation rate in clusters (i.e. the total star formation rate within 0.5xR200 from the cluster center divided by the cluster dynamical mass) rapidly increases with look-back time following approximately ~(1+z)^6, and it is also correlated with the cluster mass.
Discovery of nine extended ionized gas clouds in a z=0.4 cluster
Masafumi Yagi,Liyi Gu,Yusei Koyama,Fumiaki Nakata,Tadayuki Kodama,Takashi Hattori,Michitoshi Yoshida
Physics , 2013,
Abstract: From deep H-alpha imaging data of Suprime-Cam/Subaru, we discovered nine extended ionized gas clouds (EIG) around galaxies in Abell 851 cluster (A851) at z=0.4. We surveyed 30 x 25 arcmin region, and the EIGs were found only near the cluster center (<2.3 arcmin ~ 750 kpc). The parent galaxies of the EIGs are star-forming or post-starburst galaxies, all of which are spectroscopically confirmed members of the cluster. Four out of the nine parent galaxies show distortion of stellar distribution in the disk, which can be a sign of recent interaction, and the interaction may have made EIGs. On the other hand, six parent galaxies (one overlaps those exhibiting distortion) show H-alpha emission without stars, which implies a ram pressure stripping.The spe ctrum of the brightest parent galaxy shows a post-starburst signature, and resembles the H-alpha stripped galaxies found in the Coma cluster. Meanwhile, two brightest parent galaxies in A851 are more massive than the EIG parent galaxies in the Coma cluster. This is consistent with "downsizing" of star-forming galaxies, though it is still in a statistical fluctuation. We also analyzed Suprime-Cam data of another z=0.39 cluster, CL0024+17, but found no EIGs. The key difference between A851 and CL0024+17 would be the existence of a subcluster colliding with the main body of A851, in which six or seven out of the nine parent galaxies in A851 exist, and the fraction of EIGs in the subcluster is significantly higher than the main subcluster of A851 and CL0024+17.
Re-calibration of SDF/SXDS Photometric Catalogs of Suprime-Cam with SDSS Data Release 8
Masafumi Yagi,Nao Suzuki,Hitomi Yamanoi,Hisanori Furusawa,Fumiaki Nakata,Yutaka Komiyama
Physics , 2012, DOI: 10.1093/pasj/65.1.22
Abstract: We present photometric recalibration of the Subaru Deep Field (SDF) and Subaru/XMM-Newton Deep Survey (SXDS). Recently, Yamanoi et al. (2012) suggested the existence of a discrepancy between the SDF and SXDS catalogs. We have used the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) catalog and compared stars in common between SDF/SXDS and SDSS. We confirmed that there exists a 0.12 mag offset in B-band between the SDF and SXDS catalogs. Moreover, we found that significant zero point offsets in i-band (~ 0.10 mag) and z-band (~ 0.14 mag) need to be introduced to the SDF/SXDS catalogs to make it consistent with the SDSS catalog. We report the measured zero point offsets of five filter bands of SDF/SXDS catalogs. We studied the potential cause of these offsets, but the origins are yet to be understood.
Combined ablation of atrial fibrillation and minimally invasive mitral valve surgery: a case report
Hironori Izutani, Masahiro Ryugo, Fumiaki Shikata, Masashi Kawamura, Tatsuhiro Nakata, Toru Okamura, Takumi Yasugi, Mitsugi Nagashima, Kanji Kawachi
Journal of Cardiothoracic Surgery , 2010, DOI: 10.1186/1749-8090-5-79
Abstract: Minimally invasive cardiac surgery with partial sternotomy for valvular heart disease has been performed for more than a decade. A partial lower sternotomy and an extended transseptal incision provide excellent exposure for minimally invasive mitral valve surgery [1,2]. We have experienced sixty minimally invasive surgeries with partial sternotomy since 2004. This approach provides excellent results in less pain, less blood loss, lower rate of wound complications, shorter length of hospital stay, and excellent cosmetics. However, there is a challenge in the patient who requires combined ablation of atrial fibrillation because of possible conduction system disturbance caused by the extended transseptal approach. We carried out cryoablation in three patients for chronic atrial fibrillation with good clinical results using a T-shaped cryoprobe with a lesion set of pulmonary vein isolation and ablation of the left and right isthmus in performing minimally invasive mitral valve surgery. We describe our technique for a creation of a lesion set for ablation of atrial fibrillation using the transseptal approach to the mitral valve through a partial lower sternotomy incision.A 72-year-old man with a history of chronic atrial fibrillation recently experienced palpitation and dyspnea on effort. His echocardiography showed an atrial septal defect, moderate mitral regurgitation, moderate tricuspid regurgitation, and slightly reduced left ventricular function with an ejection fraction of 49%. His cardiac catheterization studies showed the Qp/Qs of 3.46 and mean pulmonary pressure of 23 mmHg. The patient was recommended to undergo mitral valve repair, tricuspid valve repair, atrial septal defect closure, and ablation of atrial fibrillation. A seven centimeter midline chest skin incision was made. The sternal saw was used to perform partial sternotomy from the right second intercostal space down to the xyphoid. A 7 mm soft-flow aortic cannula was placed on the ascending aorta. Bica
Probing the evolution of early-type galaxies using multi-colour number counts and redshift distributions
Fumiaki Nakata,Kazuhiro Shimasaku,Mamoru Doi,Nobunari Kashikawa,Wataru Kawasaki,Yutaka Komiyama,Sadanori Okamura,Maki Sekiguchi,Masafumi Yagi,Naoki Yasuda
Physics , 1999, DOI: 10.1046/j.1365-8711.1999.03051.x
Abstract: We investigate pure luminosity evolution models for early-type (elliptical and S0) galaxies (i.e., no number density change or morphology transition), and examine whether these models are consistent with observed number counts in the B, I and K bands and redshift distributions of two samples of faint galaxies selected in the I and K bands. The models are characterized by the star formation time scale $\tau_{SF}$ and the time $t_{gw}$ when galactic wind blows in addition to several other conventional parameters. We find the single-burst model ($\tau_{SF}$=0.1 Gyr and $t_{gw}$=0.353 Gyr), which is known to reproduce the photometric properties of early-type galaxies in clusters, is inconsistent with redshift distributions of early-type galaxies in the field environment due to overpredictions of galaxies at $z\gsim1.4$ even with strong extinction which is at work until $t_{gw}$. In order for dust extinction to be more effective, we change $\tau_{SF}$ and $t_{gw}$ as free parameters, and find that models with $\tau_{SF}\gsim0.5$ Gyr and $t_{gw}>1.0$ Gyr can be made consistent with both the observed redshift distributions and number counts, if we introduce strong extinction $(E(B-V)\geq1$ as a peak value). These results suggest that early-type galaxies in the field environment do not have the same evolutionary history as described by the single-burst model.
Large-scale environment of z~5.7 CIV absorption systems I: projected distribution of galaxies
C. Gonzalo Díaz,Yusei Koyama,Emma V. Ryan-Weber,Jeff Cooke,Masami Ouchi,Kazuhiro Shimasaku,Fumiaki Nakata
Physics , 2014, DOI: 10.1093/mnras/stu914
Abstract: Metal absorption systems are products of star formation. They are believed to be associated with massive star forming galaxies, which have significantly enriched their surroundings. To test this idea with high column density CIV absorption systems at z~5.7, we study the projected distribution of galaxies and characterise the environment of CIV systems in two independent quasar lines-of-sight: J103027.01+052455.0 and J113717.73+354956.9. Using wide field photometry (~80x60h$^{-1}$ comoving Mpc), we select bright (Muv(1350\AA)<-21.0 mag.) Lyman break galaxies (LBGs) at z~5.7 in a redshift slice \Delta z~0.2 and we compare their projected distribution with z~5.7 narrow-band selected Lyman alpha emitters (LAEs, \Delta z~0.08). We find that the CIV systems are located more than 10h$^{-1}$ projected comoving Mpc from the main concentrations of LBGs and no candidate is closer than ~5h$^{-1}$ projected comoving Mpc. In contrast, an excess of LAEs -lower mass galaxies- is found on scales of ~10h$^{-1}$ comoving Mpc, suggesting that LAEs are the primary candidates for the source of the CIV systems. Furthermore, the closest object to the system in the field J1030+0524 is a faint LAE at a projected distance of 212h$^{-1}$ physical kpc. However, this work cannot rule out undiscovered lower mass galaxies as the origin of these absorption systems. We conclude that, in contrast with lower redshift examples (z<3.5), strong CIV absorption systems at z~5.7 trace low-to-intermediate density environments dominated by low-mass galaxies. Moreover, the excess of LAEs associated with high levels of ionizing flux agrees with the idea that faint galaxies dominate the ionizing photon budget at this redshift.
On the evolution and environmental dependence of the star formation rate versus stellar mass relation since z~2
Yusei Koyama,Ian Smail,Jaron Kurk,James E. Geach,David Sobral,Tadayuki Kodama,Fumiaki Nakata,A. M. Swinbank,Philip N. Best,Masao Hayashi,Ken-ichi Tadaki
Physics , 2013, DOI: 10.1093/mnras/stt1035
Abstract: This paper discusses the evolution of the correlation between galaxy star formation rates (SFRs) and stellar mass (M*) over the last ~10 Gyrs, particularly focusing on its environmental dependence. We first present the mid-infrared (MIR) properties of the H-alpha-selected galaxies in a rich cluster Cl0939+4713 at z=0.4. With a MIR stacking analysis, we find that the median SFR of H-alpha emitters is higher in higher-density environment at z=0.4. We also find that star-forming galaxies in high-density environment tend to have higher specific SFR (SSFR), although the trend is much less significant compared to that of SFR. This increase of SSFR in high-density environment is not visible when we consider the SFR derived from H-alpha alone, suggesting that the dust attenuation in galaxies depends on environment; galaxies in high-density environment tend to be dustier (by up to ~0.5 mag). We then discuss the environmental dependence of the SFR-M* relation for star-forming galaxies since z~2, by compiling our comparable, narrow-band selected, large H-alpha emitter samples in both distant cluster environments (from MAHALO-Subaru) and field environments (from HiZELS). We find that the SSFR of H-alpha-selected galaxies (at the fixed mass of log(M*/Msun)=10) rapidly evolves as (1+z)^3, but the SFR-M* relation is independent of the environment since z~2, as far as we rely on the H-alpha-based SFRs (with M*-dependent extinction correction). Even if we consider the possible environmental variation in the dust attenuation, we conclude that the difference in the SFR-M* relation between cluster and field star-forming galaxies is always small (~<0.2dex level) at any time in the history of the Universe since z~2. [abridged]
Clustering Properties of Galaxies at z~4 in the Subaru/XMM Deep Survey Field
Masami Ouchi,Kazuhiro Shimasaku,Sadanori Okamura,Mamoru Doi,Hisanori Furusawa,Masaru Hamabe,Masahiko Kimura,Yutaka Komiyama,Masayuki Miyazaki,Satoshi Miyazaki,Fumiaki Nakata,Maki Sekiguchi,Masafumi Yagi,Naoki Yasuda
Physics , 2001, DOI: 10.1086/323598
Abstract: We study the clustering properties of about 1200 z~4 Lyman Break Galaxy (LBG) candidates with i'<26 which are selected by color from deep BRi' imaging data of a 618 arcmin^2 area in the Subaru/XMM-Newton Deep Field taken with Subaru Prime Focus Camera. The contamination and completeness of our LBG sample are evaluated, on the basis of the Hubble Deep Field North (HDFN) objects, to be 17% and 45%, respectively. We derive the angular correlation function over theta = 2''-1000'', and find that it is fitted fairly well by a power law, omega(theta)=A_omega theta^{-0.8}, with A_omega = 0.71 +/- 0.26. We then calculate the correlation length r0 (in comoving units) of the two-point spatial correlation function xi(r) = (r/r0)^{-1.8} from A_omega using the redshift distribution of LBGs derived from the HDFN, and find r0=2.7 (+0.5/-0.6) h^{-1} Mpc in a Lambda-dominated universe (Omega_m=0.3 and Omega_Lambda=0.7). This is twice larger than the correlation length of the dark matter at z~4 predicted from an analytic model by Peacock & Dodds but about twice smaller than that of bright galaxies predicted by a semi-analytic model of Baugh et al. We find an excess of omega(theta) on small scales (theta < 5'') departing from the power law fit over 3 sigma significance levels. Interpreting this as due to galaxy mergers, we estimate the fraction of galaxies undergoing mergers in our LBG sample to be 3.0 +/- 0.9%, which is significantly smaller than those of galaxies at intermediate redshifts.
Statistical Properties of Lyman Break Galaxies at z~4
Masami Ouchi,Kazuhiro Shimasaku,Sadanori Okamura,Mamoru Doi,Hisanori Furusawa,Masaru Hamabe,Masahiko Kimura,Yutaka Komiyama,Masayuki Miyazaki,Satoshi Miyazaki,Fumiaki Nakata,Maki Sekiguchi,Masafumi Yagi,Naoki Yasuda
Physics , 2001,
Abstract: We study the luminosity function and the correlation function of about 1200 z~4 Lyman break galaxies (LBGs) with i'<26 that are photometrically selected from deep BRi' imaging data of a 618 arcmin^2 area in the Subaru/XMM-Newton Deep Field taken with Subaru Prime Focus Camera. The contamination and completeness of our LBG sample are evaluated, on the basis of the Hubble Deep Field-North (HDF-N) objects, to be 17% and 45%, respectively. We derive the UV (rest 1700A) luminosity functions (LFs) and find a large population of UV-luminous galaxies at z~4. The LFs of the red and blue subsamples imply that the bright LBGs are redder in the UV continuum than the average color of the LBGs. Then we calculate the correlation function over theta = 2''-1000'' and find that it is fitted fairly well by a power law, omega(theta)=A_omega theta^(-0.8), with A_omega=0.71 +/- 0.26. We estimate the correlation length r_0 (in comoving units) of the two-point spatial correlation function xi(r) = (r/r_0)^(-1.8) to be r_0=2.7 +0.5/-0.6 h^(-1) Mpc (Omega_m=0.3 and Omega_Lambda=0.7). The correlation function shows an excess of omega (theta) on small scales (theta < 5''), departing from the power-law fit at > 3 sigma significance level. Interpreting this as being due to galaxy mergers, we evaluate the fraction of galaxies undergoing mergers to be 3.0 +/- 0.9%, which is significantly smaller than those of galaxies at intermediate redshifts.
Behaviors of Crystallization for Osmotic Pressure under Microwave Irradiation  [PDF]
Ryosuke Nakata, Yusuke Asakuma
Journal of Crystallization Process and Technology (JCPT) , 2015, DOI: 10.4236/jcpt.2015.51002
Abstract: We studied chemical garden in order to investigate precipitation behavior for osmotic pressure under microwave irradiation. The salt concentration and microwave irradiation power were varied. Microwave irradiation induced release of osmotic pressure and change of precipitation pattern because polar molecules vibrate and rotate in an electromagnetic field. For example, the width of precipitation increased and the number of rapture of the membrane decreased due to the release of osmotic pressure by the irradiation. Accordingly, microwave irradiation accelerated the diffusion of ionic molecules through the membrane.
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