Atmospheric Responses to Arctic Climate Warming: Precipitation, Cyclone, and Synoptic Patterns

In recent decades, a rapidly warming lower atmosphere has been observed in the Arctic. Consequently, we wish to address a fundamental question: how do weather patterns in the northern hemisphere respond to these significant changes in the Arctic, especially sea ice loss? To gain insight about the possible linkage between warming Arctic conditions and the resultant atmospheric responses, changes in cyclone activity and synoptic weather patterns were investigated in this study. Given that precipitation can also affect weather patterns, a newly developed reanalysis precipitation was evaluated over Greenland for future hydrological cycle research in the Arctic.First, the Arctic System Reanalysis version 1 precipitation generally showed good agreement with gauge-based precipitation measured in coastal areas. However, precipitation at Summit, Greenland, a higher continental environment, indicated overestimated amounts with respect to Doppler radar measurements.Secondly, no robust changes in cyclone activity were observed, despite the changes in moisture availability, regional baroclinicity, and vertical stability. Lastly, we confirmed that persistent warm surface signals can generate a ridge at 500 hPa and a surface high-pressure system downstream of the ridge. When the Arctic surface forcing has a sufficiently long persistence over a moderately large area, it can induce mid-latitude cold-air advection

Enhanced Star Formation of Less Massive Galaxies in a Proto-Cluster at z=2.5

We investigate a correlation between star-formation rate (SFR) and stellar mass for Halpha emission line galaxies (HAEs) in one of the richest proto-clusters ever known at z~2.5, USS 1558-003 proto-cluster. This study is based on a 9.7-hour narrow-band imaging data with MOIRCS on the Subaru telescope. We are able to construct a sample, in combination with additional H-band data taken with WFC3 on Hubble Space Telescope (HST), of 100 HAEs reaching the dust-corrected SFRs down to 3 Msun/yr and the stellar masses down to $10^{8.0}$ Msun. We find that while the star-forming galaxies with >$10^{9.3}$ Msun are located on the universal SFR-mass main sequence irrespective of the environment, less massive star-forming galaxies with <$10^{9.3}$ Msun show a significant upward scatter from the main sequence in this proto-cluster. This suggests that some less massive galaxies are in a starburst phase, although we do not know yet if this is due to environmental effects.Comment: 5 pages, 3 figures, 1 table, accepted for publication in the ApJ Letter

Evolutionary phases of gas-rich galaxies in a galaxy cluster at z=1.46

We report a survey of molecular gas in galaxies in the XMMXCS J2215.9-1738 cluster at $z=1.46$. We have detected emission lines from 17 galaxies within a radius of $R_{200}$ from the cluster center, in Band 3 data of the Atacama Large Millimeter/submillimeter Array (ALMA) with a coverage of 93 -- 95 GHz in frequency and 2.33 arcmin$^2$ in spatial direction. The lines are all identified as CO $J$=2--1 emission lines from cluster members at $z\sim1.46$ by their redshifts and the colors of their optical and near-infrared (NIR) counterparts. The line luminosities reach down to $L'_{\rm CO(2-1)}=4.5\times10^{9}$ K km s$^{-1}$ pc$^2$. The spatial distribution of galaxies with a detection of CO(2--1) suggests that they disappear from the very center of the cluster. The phase-space diagram showing relative velocity versus cluster-centric distance indicates that the gas-rich galaxies have entered the cluster more recently than the gas-poor star-forming galaxies and passive galaxies located in the virialized region of this cluster. The results imply that the galaxies have experienced ram-pressure stripping and/or strangulation during the course of infall towards the cluster center and then the molecular gas in the galaxies at the cluster center is depleted by star formation.Comment: 7 pages, 4 figures, 1 table, accepted for publication in the ApJ Letter

Similarities and uniqueness of Lyα\alpha emitters among star-forming galaxies at z=2.5

We conducted a deep narrow-band imaging survey with the Subaru Prime Focus Camera on the Subaru Telescope and constructed a sample of Ly$\alpha$ emitters (LAEs) at z=2.53 in the UDS-CANDELS field where a sample of H$\alpha$ emitters (HAEs) at the same redshift is already obtained from our previous narrow-band observation at NIR. The deep narrow-band and multi broadband data allow us to find LAEs of stellar masses and star-formation rates (SFRs) down to $\gtrsim$$10^8$ M$_\odot$ and $\gtrsim$0.2 M$_\odot$/yr, respectively. We show that the LAEs are located along the same mass-SFR sequence traced by normal star-forming galaxies such as HAEs, but towards a significantly lower mass regime. Likewise, LAEs seem to share the same mass--size relation with typical star-forming galaxies, except for the massive LAEs, which tend to show significantly compact sizes. We identify a vigorous mass growth in the central part of LAEs: the stellar mass density in the central region of LAEs increases as their total galaxy mass grows. On the other hand, we see no Ly$\alpha$ line in emission for most of the HAEs. Rather, we find that the Ly$\alpha$ feature is either absent or in absorption (Ly$\alpha$ absorbers; LAAs), and its absorption strength may increase with reddening of the UV continuum slope. We demonstrate that a deep Ly$\alpha$ narrow-band imaging like this study is able to search for not only LAEs but also LAAs in a certain redshift slice. This work suggests that LAEs trace normal star-forming galaxies in the low-mass regime, while they remain as a unique population because the majority of HAEs are not LAEs.Comment: 20 pages, 18 figures, 3 tables, accepted for publication in MNRA

Trends in the Nontuberculous Mycobacterial Disease Mortality Rate in Japan: A Nationwide Observational Study, 1997–2016

Background. The incidence of nontuberculous mycobacterial (NTM) infections has been increasing worldwide, becoming a significant healthcare burden especially among elderly people. This study aimed to evaluate the trends in NTM-associated mortality in Japan. Methods. This study used vital statistics data and data on all NTM-associated deaths (N = 18 814) among individuals aged >= 40 years in Japan from 1997 to 2016. We calculated the crude and age-adjusted mortality rates by age and sex and used joinpoint regression to analyze trends and estimate the average annual percentage change (AAPC). We compared crude NTM- and tuberculosis-associated mortality rates by sex. Results. The overall crude annual mortality rate increased from 0.63/100 000/year in 1997 to 1.93/100 000/year in 2016 and was the highest among individuals aged 80-84 years. The AAPC of the crude mortality rates among men of all ages and women aged 40-59 years were stable but increased among women aged 60-79 years (3.5%; 95% confidence interval [CI ], 2.8-4.3) and >= 80 years (4.3%; 95% CI, 3.7-4.9). Among men, the age-adjusted mortality rates did not show a significant trend, while among women, the rates increased over the study period (AAPC, 4.6%; 95% CI, 2.7-6.6). In women, the crude NTM-associated mortality rate exceeded the tuberculosis mortality rate in 2014, 2015, and 2016. Conclusions. NTM mortality increased in Japan between 1997 and 2016, especially among the elderly female population. Given the increasing NTM-associated mortality and the susceptible aging population, public health authorities in Japan should pay greater attention to NTM infections