31 research outputs found
Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region
We have performed a systematic study of several regions in the sky where the
number of galaxies exhibiting star formation (SF) activity is greater than
average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced
sample. By statistically comparing the KUG and non-KUG distributions, we
discovered four KUG-rich regions with a size of . One of these regions corresponds spatially to a filament of length
Mpc in the Lynx-Ursa Major region (). We call this ``the Lynx-Ursa
Major (LUM) filament''. We obtained surface photometry of 11 of
the KUGs in the LUM filament and used these to investigate the integrated
colors, distribution of SF regions, morphologies, and local environments. We
found that these KUGs consist of distorted spiral galaxies and compact galaxies
with blue colors. Their star formation occurs in the entire disk, and is not
confined to just the central regions. The colors of the SF regions imply that
active star formation in the spiral galaxies occurred yr ago,
while that of the compact objects occurred yr ago. Though the
photometric characteristics of these KUGs are similar to those of interacting
galaxies or mergers, most of these KUGs do not show direct evidence of merger
processes.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The
Title of the previous one was truncated by the author's mistake, and is
corrected. Main body of the paper is unchange
A search for steep spectrum radio relics and halos with the GMRT
Context: Diffuse radio emission, in the form of radio halos and relics,
traces regions in clusters with shocks or turbulence, probably produced by
cluster mergers. Some models of diffuse radio emission in clusters indicate
that virtually all clusters should contain diffuse radio sources with a steep
spectrum. External accretion shocks associated with filamentary structures of
galaxies could also accelerate electrons to relativistic energies and hence
produce diffuse synchrotron emitting regions. Here we report on Giant Metrewave
Radio Telescope (GMRT) observations of a sample of steep spectrum sources from
the 74 MHz VLSS survey. These sources are diffuse and not associated with
nearby galaxies.
Aims: The main aim of the observations is to search for diffuse radio
emission associated with galaxy clusters or the cosmic web.
Methods: We carried out GMRT 610 MHz continuum observations of unidentified
diffuse steep spectrum sources.
Results: We have constructed a sample of diffuse steep spectrum sources,
selected from the 74 MHz VLSS survey. We identified eight diffuse radio sources
probably all located in clusters. We found five radio relics, one cluster with
a giant radio halo and a radio relic, and one radio mini-halo. By complementing
our observations with measurements from the literature we find correlations
between the physical size of relics and the spectral index, in the sense that
smaller relics have steeper spectra. Furthermore, larger relics are mostly
located in the outskirts of clusters while smaller relics are located closer to
the cluster center.Comment: 20 pages, 26 figures, accepted for publication in A&A on October 7,
200
Quiescent Isolation: The Extremely Extended HI Halo of the Optically Compact Dwarf Galaxy ADBS 113845+2008
We present new optical imaging and spectroscopy and HI spectral line imaging
of the dwarf galaxy ADBS 113845+2008 (hereafter ADBS 1138). This metal-poor
(Z~30% Z_Sun), "post-starburst" system has one of the most compact stellar
distributions known in any galaxy to date (B-band exponential scale length
=0.57 kpc). In stark contrast to the compact stellar component, the neutral gas
is extremely extended; HI is detected to a radial distance of ~25 kpc at the
10^19 cm^-2 level (>44 B-band scale lengths). Comparing to measurements of
similar "giant disk" dwarf galaxies in the literature, ADBS 1138 has the
largest known HI-to-optical size ratio. The stellar component is located near
the center of a broken ring of HI that is ~15 kpc in diameter; column densities
peak in this structure at the ~3.5x10^20 cm^-2 level. At the center of this
ring, in a region of comparatively low HI column density, we find ongoing star
formation traced by H alpha emission. We sample the rotation curve to the point
of turn over; this constrains the size of the dark matter halo of the galaxy,
which outweighs the luminous component (stars + gas) by at least a factor of
15. To explain these enigmatic properties, we examine "inside-out" and
"outside-in" evolutionary scenarios. Calculations of star formation energetics
indicate that "feedback" from concentrated star formation is not capable of
producing the ring structure; we posit that this is a system where the large HI
disk is evolving in quiescent isolation. In a global sense, this system is
exceedingly inefficient at converting neutral gas into stars.Comment: Astrophysical Journal, in pres
The Second Byurakan Survey Galaxies. I. The Optical Database
A database for the entire catalog of the Second Byurakan Survey (SBS)
galaxies is presented. It contains new measurements of their optical parameters
and additional information taken from the literature and other databases. The
measurements were made using Ipg(near-infrared), Fpg(red) and Jpg(blue) band
images from photographic sky survey plates obtained by the Palomar Schmidt
telescope and extracted from the STScI Digital Sky Survey (DSS). The database
provides accurate coordinates, morphological type, spectral and activity
classes, apparent magnitudes and diameters, axial ratios, and position angles,
as well as number counts of neighboring objects in a circle of radius 50 kpc.
The total number of individual SBS objects in the database is now 1676. The 188
Markarian galaxies which were re-discovered by SBS are not included in this
database. We also include redshifts that are now available for 1576 SBS
objects, as well as 2MASS infrared magnitudes for 1117 SBS galaxies.Comment: 13 pages, 1 figure, 1 tabl
A randomized phase II trial of erlotinib versus S-1 as a third- or fourth-line therapy for patients with wild-type EGFR non-small cell lung cancer (HOT1002)
Purpose: A high proportion of patients with wild-type EGFR non-small cell lung cancer (NSCLC) receive third-line therapy and beyond, with no prospective randomized trials addressing the issue. This study aimed to select the most suitable regimen as a third- or fourth-line therapy for wild-type EGFR NSCLC. Methods: This multicenter, randomized phase II study in Japan included patients with recurrent or advanced NSCLC with wild-type or unknown EGFR, who progressed after two or three previous chemotherapies. The patients were randomly assigned to erlotinib (150 mg/day, days 1-21) or S-1 (80-120 mg/day, days 1-14) every 3 weeks until disease progression or unacceptable toxicity. The primary endpoint was disease control rate (DCR). The secondary endpoints included overall survival (OS), progression-free survival (PFS), objective response rate (ORR), toxicity, and quality of life (QOL). Results: From 2011 to 2016, 37 patients were randomly assigned to receive erlotinib (E arm, n = 19) and S-1 (S arm, n = 18). This study was terminated prematurely because of poor patient accrual. DCR/ORR were 42.1%/15.8% in the E arm and 66.7%/16.7% in the S arm. Median PFS/OS were 1.6 months/8.0 months in the E arm and 3.3 months/12.2 months in the S arm. In both groups, the most commonly reported grade 3-4 toxicities were fatigue, anorexia, and nausea. One grade 5 pneumonitis occurred in the S arm. No significant difference was seen in QOL. Conclusions: S-1 as a third- or fourth-line therapy for wild-type EGFR NSCLC showed numerically better clinical outcomes than erlotinib. Clinical trial registration no. UMIN000005308