243 research outputs found
Super-solar N/C in the NLS1 Galaxy Markarian 1044
Narrow-Line Seyfert 1s (NLS1s) are known to have extreme values of a number
of properties compared to Active Galactic Nuclei (AGN) as a class. In
particular, previous emission-line studies have suggested that NLS1s are
unusually metal rich compared to broad-line AGN of comparable luminosity. We
present low- and medium-resolution spectroscopic observations of the NLS1
Markarian 1044 with the Hubble Space Telescope Imaging Spectrometer (STIS). We
identify two blueshifted intrinsic absorption systems at -1145 and -295 km/s
relative to the systemic velocity of the galaxy. Using a simple photoionization
model of the absorbing gas, we find that the strongest and best-measured of the
absorption systems has N/C approximately 6.96 times the solar value. We also
report on the discovery of three new Ly-alpha forest lines with neutral
Hydrogen column density log greater than 12.77 in the log. This number is
consistent with the 2.6 expected in the path length to the source redshift of
Mrk 1044.Comment: Submitted to ApJ. 21 pages including 4 figures & 5 table
Super-solar Metallicity in the NLS1 Galaxy Markarian 1044
The determination of the bulk metallicity and the abundance mixture of
various elements is very difficult in quasars and AGNs because only a few lines
are observed and the ionization correction is unknown. Most abundance studies
of AGNs assume the N/C ratio scales as metallicity (nitrogen goes as
metallicity squared) and so serves as a metallicity indicator. We present an
accurate metallicity determination of the narrow-line Seyfert 1 (NLS1) galaxy
Markarian 1044, using O VI column density measurements from the Far Ultraviolet
Spectroscopic Explorer (FUSE) together with C IV, N V, and H I from Hubble
Space Telescope (HST) observations. In this absorption line study we find that
the circumnuclear gas in Mrk 1044 has a metallicity of at least five times
solar. This is consistent with the expectation that NLS1s have a high
metallicity, similar to that found in high-redshift quasars. More surprisingly,
we find that the absorbing material requires a near-solar mixture. In other
words, the N/C is consistent with the solar ratio, and does not scale with the
metallicity. This suggests that the chemical enrichment scenario for this
object, and perhaps for AGNs in general, may be different from the traditional
model of galactic metal enrichment, at least in the high-metallicity regime.Comment: 14 pages, 3 Tables, 6 Figures, Submitted to Ap
Metallicity measurements in AGNs
Measuring metallicity in the nuclear regions of AGNs is difficult because
only a few lines are observed and ionization correction becomes a major
problem. Nitrogen to carbon ratio has been widely used as an indicator for
metallicity, but precise measurements have been lacking. We made such
measurements for the first time using a wide baseline of ionization states with
observations from FUSE, HST and Chandra. OVI observations with FUSE were
crucial in this effort. We measured super-solar metallicities in two AGNs and
found that N/C does not scale with metallicity. This suggests that chemical
enrichment scenario in nuclear regions of galaxies may be different from
traditional models of metal enrichment.Comment: To appear in Future Directions in Ultraviolet Astronomy (AIP Conf
Proc), Ed. Michael E. Van Steenber
Characterizing Cosmic-Ray Propagation in Massive Star-forming Regions: The Case of 30 Doradus and the Large Magellanic Cloud
Using infrared, radio, and γ-ray data, we investigate the propagation characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus (30 Dor) star-forming region in the Large Magellanic Cloud (LMC) using a phenomenological model based on the radio-far-infrared correlation within galaxies. Employing a correlation analysis, we derive an average propagation length of ~100-140 pc for ~3 GeV CR electrons resident in 30 Dor from consideration of the radio and infrared data. Assuming that the observed γ-ray emission toward 30 Dor is associated with the star-forming region, and applying the same methodology to the infrared and γ-ray data, we estimate a ~20 GeV propagation length of 200-320 pc for the CR nuclei. This is approximately twice as large as for ~3 GeV CR electrons, corresponding to a spatial diffusion coefficient that is ~4 times higher, scaling as (R/GV)δ with δ ≈ 0.7-0.8 depending on the smearing kernel used in the correlation analysis. This value is in agreement with the results found by extending the correlation analysis to include ~70 GeV CR nuclei traced by the 3-10 GeV γ-ray data (δ ≈ 0.66 ± 0.23). Using the mean age of the stellar populations in 30 Dor and the results from our correlation analysis, we estimate a diffusion coefficient D_R ≈ (0.9-1.0) × 10^(27)(R/GV)0.7 cm^(2) s^(–1). We compare the values of the CR electron propagation length and surface brightness for 30 Dor and the LMC as a whole with those of entire disk galaxies. We find that the trend of decreasing average CR propagation distance with increasing disk-averaged star formation activity holds for the LMC, and extends down to single star-forming regions, at least for the case of 30 Dor
Disrupted Brain Circuitry for Pain‐Related Reward/Punishment in Fibromyalgia
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102040/1/art38191.pd
Supermassive black holes, pseudobulges, and the narrow-line Seyfert 1 galaxies
We present HST/ACS observations of ten galaxies that host narrow-line Seyfert
1 (NLS1) nuclei, believed to contain relatively smaller mass black holes
accreting at high Eddington ratios. We deconvolve each ACS image into a nuclear
point source (AGN), a bulge, and a disk, and fitted the bulge with a Sersic
profile and the disk with an exponential profile. We find that at least five
galaxies can be classified as having pseudobulges. All ten galaxies lie below
the \mbh--L relation, confirming earlier results. Their locus is
similar to that occupied by pseudobulges. This leads us to conclude that the
growth of BHs in NLS1s is governed by secular processes rather than
merger-driven. Active galaxies in pseudobulges point to an alternative track of
black hole--galaxy co-evolution. Because of the intrinsic scatter in black hole
mass--bulge properties scaling relations caused by a combination of factors
such as the galaxy morphology, orientation, and redshift evolution, application
of scaling relations to determine BH masses may not be as straightforward as
has been hoped.Comment: Replaced with accepted versio
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