474 research outputs found
First Census of Gas-phase Metallicity Gradients of Star-forming Galaxies in Overdense Environments at Cosmic Noon
We report the first spatially resolved measurements of gas-phase metallicity
radial gradients in star-forming galaxies in overdense environments at
. The spectroscopic data are acquired by the \mg\ survey, a Hubble
Space Telescope (HST) cycle-28 medium program. This program is obtaining 45
orbits of WFC3/IR grism spectroscopy in the density peak regions of three
massive galaxy protoclusters (BOSS 1244, BOSS 1542 and BOSS 1441) at .
Our sample in the BOSS 1244 field consists of 20 galaxies with stellar-mass
ranging from to \Msun\ , star formation rate (SFR) from
10 to 240 \Msun\,yr, and global gas-phase metallicity (\oh) from 8.2 to
8.6. At confidence level, 2/20 galaxies in our sample show positive
(inverted) gradients -- the relative abundance of oxygen increasing with
galactocentric radius, opposite the usual trend. Furthermore, 1/20 shows
negative gradients and 17/20 are consistent with flat gradients. This high
fraction of flat/inverted gradients is uncommon in simulations and previous
observations conducted in blank fields at similar redshifts. To understand
this, we investigate the correlations among various observed properties of our
sample galaxies. We find an anticorrelation between metallicity gradient and
global metallicity of our galaxies residing in extreme overdensities, and a
marked deficiency of metallicity in our massive galaxies as compared to their
coeval field counterparts. We conclude that the cold-mode gas accretion plays
an active role in shaping the chemical evolution of galaxies in the
protocluster environments, diluting their central chemical abundance, and
flattening/inverting their metallicity gradients.Comment: 13 pages, 6 figures, 1 table. Accepted for publication in ApJ
The Different Nature in Seyfert 2 Galaxies With and Without Hidden Broad-Line Regions
We compile a large sample of 120 Seyfert 2 galaxies (Sy2s) which contains 49
hidden broad-line region (HBLR) Sy2s and 71 non-HBLR Sy2s. From the difference
in the power sources between two groups, we test if HBLR Sy2s are dominated by
active galactic nuclei (AGNs), and if non-HBLR Sy2s are dominated by
starbursts. We show that: (1) HBLR Sy2s have larger accretion rates than
non-HBLR Sy2s; (2) HBLR Sy2s have larger \Nev /\Neii and \oiv /\Neii line ratios than non-HBLR
Sy2s; (3) HBLR Sy2s have smaller flux ratio which shows
the relative strength of the host galaxy and nuclear emission than non-HBLR
Sy2s. So we suggest that HBLR Sy2s and non-HBLR Sy2s are AGN-dominated and
starburst-dominated, respectively. In addition, non-HBLR Sy2s can be classified
into the luminous () and less luminous
() samples, when considering only
their obscuration. We suggest that: (1) the invisibility of polarized broad
lines (PBLs) in the luminous non-HBLR Sy2s depends on the obscuration; (2) the
invisibility of PBLs in the less luminous non-HBLR Sy2s depends on the very low
Eddington ratio rather than the obscuration.Comment: Accepted by ApJ, 11 pages, 4 figure
Systematic biases in determining dust attenuation curves through galaxy SED fitting
While the slope of the dust attenuation curve () is found to
correlate with effective dust attenuation () as obtained through spectral
energy distribution (SED) fitting, it remains unknown how the fitting
degeneracies shape this relation. We examine the degeneracy effects by fitting
SEDs of a sample of local star-forming galaxies (SFGs) selected from the Galaxy
And Mass Assembly survey, in conjunction with mock galaxy SEDs of known
attenuation parameters. A well-designed declining starburst star formation
history is adopted to generate model SED templates with intrinsic UV slope
() spanning over a reasonably wide range. The best-fitting
for our sample SFGs shows a wide coverage, dramatically differing from the
limited range of for a starburst of constant star formation. Our
results show that strong degeneracies between , , and in
the SED fitting induce systematic biases leading to a false --
correlation. Our simulation tests reveal that this relationship can be well
reproduced even when a flat -- relation is taken to build the
input model galaxy SEDs. The variations in best-fitting are dominated
by the fitting errors. We show that assuming a starburst with constant star
formation in SED fitting will result in a steeper attenuation curve, smaller
degeneracy errors, and a stronger -- relation. Our findings
confirm that the -- relation obtained through SED fitting is
likely driven by the systematic biases induced by the fitting degeneracies
between , , and .Comment: 21 pages, 13 figures, accepted for publication in the MNRAS, Comments
welcome
The Physical Properties of Star-Forming Galaxies with Strong [O III] Lines at z=3.25
We present an analysis of physical properties of 34 [O III] emission-line
galaxies (ELGs) at z=3.2540.029 in the Extended Chandra Deep Field South
(ECDFS). These ELGs are selected from deep narrow H2S(1) and broad Ks imaging
of 383 arcmin obtained with CFHT/WIRCam. We construct spectral energy
distributions (SEDs) from U to Ks to derive the physical properties of ELGs.
These [O III] ELGs are identified as starburst galaxies with strong [O III]
lines of L([O III]) ~ 10 - 10 erg s, and have stellar
masses of M* ~ 10-10 M and star formation rates of ~
10-210 M yr. Our results show that 24% of our sample galaxies
are dusty with Av > 1 mag and EW(OIII) ~ 70-500 , which are often
missed in optically selected [O III] ELG samples. Their rest-frame UV and
optical morphologies from HST/ACS and HST/WFC3 deep imaging reveal that these
[O III] ELGs are mostly multiple-component systems (likely mergers) or compact.
And 20% of them are nearly invisible in the rest-frame UV owing to heavy dust
attenuation. Interestingly, we find that our samples reside in an overdensity
consisting of two components: one southeast (SE) with an overdensity factor of
~ 41 over a volume of 13 cMpc and the other
northwest (NW) with ~ 38 over a volume of 10 cMpc.
The two overdense substructures are expected to be virialized at z=0 with a
total mass of ~ 1.1 x 10 M and ~ 4.8 x 10 M, and
probably merge into a Coma-like galaxy cluster.Comment: 22 pages, 11 figures, 3 tables. Accepted for publication in Ap
Construction of a High-Density Linkage Map and QTL Fine Mapping for Growth- and Sex-Related Traits in Channel Catfish (Ictalurus punctatus)
A high-density genetic linkage map is of particular importance in the fine mapping for important economic traits and whole genome assembly in aquaculture species. The channel catfish (Ictalurus punctatus), a species native to North America, is one of the most important commercial freshwater fish in the world. Outside of the United States, China has become the major producer and consumer of channel catfish after experiencing rapid development in the past three decades. In this study, based on restriction site associated DNA sequencing (RAD-seq), a high-density genetic linkage map of channel catfish was constructed by using single nucleotide polymorphisms (SNPs) in a F1 family composed of 156 offspring and their two parental individuals. A total of 4,768 SNPs were assigned to 29 linkage groups (LGs), and the length of the linkage map reached 2,480.25 centiMorgans (cM) with an average distance of 0.55 cM between loci. Based on this genetic linkage map, 223 genomic scaffolds were anchored to the 29 LGs of channel catfish, and a total length of 704.66 Mb was assembled. Quantitative trait locus (QTL) mapping and genome-wide association analysis identified 10 QTLs of sex-related and six QTLs of growth-related traits at LG17 and LG28, respectively. Candidate genes associated with sex dimorphism, including spata2, spata5, sf3, zbtb38, and fox, were identified within QTL intervals on the LG17. A sex-linked marker with simple sequence repeats (SSR) in zbtb38 gene of the LG17 was validated for practical verification of sex in the channel catfish. Thus, the LG17 was considered as a sex-related LG. Potential growth-related genes were also identified, including important regulators such as megf9, npffr1, and gas1. In a word, we constructed the high-density genetic linkage map and developed the sex-linked marker in channel catfish, which are important genetic resources for future marker-assisted selection (MAS) of this economically important teleost
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons
The branching fractions for the inclusive Cabibbo-favored ~K*0 and
Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample
of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with
the BES-II detector at the BEPC collider. The branching fractions for the
decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 ->
\~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and
BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching
fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X)
< 6.6%
Study of
New data are presented on from a sample of 58M
events in the upgraded BES II detector at the BEPC. There is a
conspicuous signal for and a peak at higher mass which
may be fitted with . From a combined analysis with
data, the branching ratio
is at the 95%
confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.
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