124 research outputs found
Effective Ex-Situ Fabrication of F-Doped SmFeAsO Wire for High Transport Critical Current Density
We demonstrate the fabrication of superconducting SmFeAsO1-xFx (Sm-1111)
wires by using the ex-situ powder-in-tube technique. Sm-1111 powder and a
binder composed of SmF3, samarium arsenide, and iron arsenide were used to
synthesize the superconducting core. Although the F content of Sm-1111 is
reduced in the process of ex-situ fabrication, the binder compensates by
sufficiently supplementing the F content, thereby preventing a decrease in the
superconducting transition temperature and a shrinkage of the superconducting
volume fraction. Thus, in the superconducting Sm-1111 wire with the binder, the
transport critical current density reaches the highest value of ~4 kA/cm2 at
4.2 K.Comment: 11 pages, 4 figure
Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097
We present the first 100 pc scale view of the dense molecular gas in the
central ~ 1.3 kpc region of the type-1 Seyfert NGC 1097 traced by HCN (J=4-3)
and HCO+ (J=4-3) lines afforded with ALMA band 7. This galaxy shows significant
HCN enhancement with respect to HCO+ and CO in the low-J transitions, which
seems to be a common characteristic in AGN environments. Using the ALMA data,
we study the characteristics of the dense gas around this AGN and search for
the mechanism of HCN enhancement. We find a high HCN (J=4-3) to HCO+ (J=4-3)
line ratio in the nucleus. The upper limit of the brightness temperature ratio
of HCN (v2=1^{1f}, J=4-3) to HCN (J=4-3) is 0.08, which indicates that IR
pumping does not significantly affect the pure rotational population in this
nucleus. We also find a higher HCN (J=4-3) to CS (J=7-6) line ratio in NGC 1097
than in starburst galaxies, which is more than 12.7 on the brightness
temperature scale. Combined from similar observations from other galaxies, we
tentatively suggest that this ratio appears to be higher in AGN-host galaxies
than in pure starburst ones similar to the widely used HCN to HCO+ ratio. LTE
and non-LTE modeling of the observed HCN and HCO+ lines using J=4-3 and 1-0
data from ALMA, and J=3-2 data from SMA, reveals a high HCN to HCO+ abundance
ratio (5 < [HCN]/[HCO+] < 20: non-LTE analysis) in the nucleus, and that the
high-J lines (J=4-3 and 3-2) are emitted from dense (10^{4.5} < n_H2 [/cc] <
10^6), hot (70 < Tkin [K] < 550) regions. Finally we propose that the high
temperature chemistry is more plausible to explain the observed enhanced HCN
emission in NGC 1097 than the pure gas phase PDR/XDR chemistry.Comment: 28 pages, 17 figures, 10 tables. Accepted to PAS
The Kiloparsec-scale Neutral Atomic Carbon Outflow in the Nearby Type-2 Seyfert Galaxy NGC 1068: Evidence for Negative AGN Feedback
Active galactic nucleus (AGN) feedback is postulated as a key mechanism for
regulating star formation within galaxies. Studying the physical properties of
the outflowing gas from AGN is thus crucial for understanding the co-evolution
of galaxies and supermassive black holes. Here we report 55 pc resolution ALMA
neutral atomic carbon [CI] observations toward the central
1 kpc of the nearby type-2 Seyfert galaxy NGC 1068, supplemented by 55 pc
resolution CO() observations. We find that [CI] emission within
the central kpc is strongly enhanced by a factor of 5 compared to the
typical [CI]/CO intensity ratio of 0.2 for nearby starburst galaxies (in
units of brightness temperature). The most [CI]-enhanced gas (ratio 1)
exhibits a kpc-scale elongated structure centered at the AGN that matches the
known biconical ionized gas outflow entraining molecular gas in the disk. A
truncated, decelerating bicone model explains well the kinematics of the
elongated structure, indicating that the [CI] enhancement is predominantly
driven by the interaction between the ISM in the disk and the highly inclined
ionized gas outflow (which is likely driven by the radio jet). Our results
strongly favor the "CO dissociation scenario" rather than the "in-situ C
formation" one which prefers a perfect bicone geometry. We suggest that the
high [CI]/CO intensity ratio gas in NGC 1068 directly traces ISM in the disk
that is currently dissociated and entrained by the jet and the outflow, i.e.,
the "negative" effect of the AGN feedback.Comment: 12 pages, 5 figures, accepted for publication in The Astrophysical
Journal Letter
ALMA Observations of the Submillimeter Dense Molecular Gas Tracers in the Luminous Type-1 Active Nucleus of NGC 7469
We present ALMA Cycle 1 observations of the central kpc region of the
luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution
(0.5 0.4 = 165 pc 132 pc) at submillimeter wavelengths.
Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3),
HCO(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860
m continuum. The region consists of the central 1 component and
the surrounding starburst ring with a radius of 1.5-2.5. Several
structures connect these components. Except for CO(3-2), these dense gas
tracers are significantly concentrated towards the central 1,
suggesting their suitability to probe the nuclear regions of galaxies. Their
spatial distribution resembles well those of centimeter and mid-infrared
continuum emissions, but it is anti-correlated with the optical one, indicating
the existence of dust obscured star formation. The integrated intensity ratios
of HCN(4-3)/HCO(4-3) and HCN(4-3)/CS(7-6) are higher at the AGN position
than at the starburst ring, which is consistent to our previous findings
(submm-HCN enhancement). However, the HCN(4-3)/HCO(4-3) ratio at the AGN
position of NGC 7469 (1.110.06) is almost half of the corresponding value
of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.00.2), despite the
more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the
ratio is comparable to that of the close vicinity of the AGN of NGC 1068
( 1.5). Based on these results, we speculate that some other heating
mechanisms than X-ray (e.g., mechanical heating due to AGN jet) can contribute
significantly for shaping the chemical composition in NGC 1097.Comment: Fixed typos in the title. 15 pages, 8 figures, 4 tables: accepted for
publication in ApJ. Comments welcom
A dibenzoylmethane derivative protects against hydrogen peroxide-induced cell death and inhibits lipopolysaccharide-induced nitric oxide production in cultured rat astrocytes.
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