72 research outputs found
A Spitzer Spectroscopic Survey of Low Ionization Nuclear Emission-line Regions: Characterization of the Central Source
We have conducted a comprehensive mid-IR spectroscopic investigation of 67
Low Ionization Nuclear Emission Line Regions (LINERs) using archival
observations from the high resolution modules of the Infrared Spectrograph on
board the Spitzer Space Telescope. Using the [NeV] 14 and 24um lines as active
galactic nuclei (AGN) diagnostics, we detect active black holes in 39% of the
galaxies in our sample, many of which show no signs of activity in either the
optical or X-ray bands. In particular, a detailed comparison of
multi-wavelength diagnostics shows that optical studies fail to detect AGN in
galaxies with large far-IR luminosities. These observations emphasize that the
nuclear power source in a large percentage of LINERs is obscured in the
optical. Indeed, the majority of LINERs show mid-IR [NeV]14/[NeV]24um flux
ratios well below the theoretical low-density limit, suggesting that there is
substantial extinction toward even the [NeV]-emitting region . Combining
optical, X-ray, and mid-IR diagnostics, we find an AGN detection rate in LINERs
of 74%, higher than previously reported statistics of the fraction of LINERs
hosting AGN. The [NeV]24um /[OIV]26um mid-IR line flux ratio in "AGN-LINERs" is
similar to that of standard AGN, suggesting that the spectral energy
distribution (SED) of the intrinsic optical/UV continuum is similar in the two.
This result is in contrast to previous suggestions of a UV deficit in the
intrinsic broadband continuum emission in AGN-LINERs. Consistent with our
finding of extinction to the [NeV]-emitting region, we propose that extinction
may also be responsible for the observed optical/UV deficit seen in at least
some AGN-LINERs.Comment: Accepted for publication in Ap
Correlated and zonal errors of global astrometric missions: a spherical harmonic solution
We propose a computer-efficient and accurate method of estimation of
spatially correlated errors in astrometric positions, parallaxes and proper
motions obtained by space and ground-based astrometry missions. In our method,
the simulated observational equations are set up and solved for the
coefficients of scalar and vector spherical harmonics representing the output
errors, rather than for individual objects in the output catalog. Both
accidental and systematic correlated errors of astrometric parameters can be
accurately estimated. The method is demonstrated on the example of the JMAPS
mission, but can be used for other projects of space astrometry, such as SIM or
JASMINE.Comment: Accepted by AJ, to be published in 201
The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer: Evidence of High Unbeamed Luminosity in Holmberg II ULX
We present the first Spitzer Infrared Spectrograph (IRS) observations of the [O IV] 25.89 micron emission line detected from the ultraluminous X-ray source (ULX) in Holmberg II. This line is a well established signature of high excitation, usually associated with AGN. Its detection suggests that the ULX has a strong impact on the surrounding gas. A Spitzer high resolution spectral map shows that the [O IV] is coincident with the X-ray position of the Holmberg II ULX. We find that the luminosity and the morphology of the line emission is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is radiation bounded both in the line of sight direction and to the west, and probably matter bounded to the east. Evidence for a massive black hole (BH) in this ULX is mounting. Detailed photoionization models favor an intermediate mass black hole of at least 85 Solar Mass as the ionization source for the [OIV] emission. We find that the spectral type of the companion star strongly affects the expected strength of the [O IV] emission. This finding could explain the origin of [O IV] in some starburst galaxies containing black hole binaries
The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. I. Observational Results for Holmberg II ULX
We presen the first Spitzer Infrared Spectrograph (IRS) observations of the [O IV] 25.89 um emission line detected from the ultraluminous X-ray source (ULX) in Holmberg II. This line is a well established signature of high excitation usually associated with AGN. Its detection suggests that the ULX has a strong impact on the surrounding gas. A Spitzer high resolution spectral map shows that the [O IV] is coincident with the X-ray position of the ULX. The ratios of the [O IV] to lower ionization lines are similar to those observed in AGN, suggesting that a strong UV and X-ray source is responsible for the, photoionization. The best XMM-Newton data is used to model the X-ray band which is then extrapolated into the UV. We perform infrared and ultraviolet photometry, and use its previously published optical and radio data to construct the full SED for the ULX and its companion. The preferred model to describe the SED includes an accretion disk which dominates the soft X-rays but contributes little at UV and optical wavelengths. The optical counterpart is consistent with a B supergiant as previously suggested in other studies. The bolometric luminosity of the ULX suggests the presence of an intermediate-mass black hole with mass >85 M for sub-Eddington accretion or, alternatively, a stellar-mass black hole that is accreting at super-Eddington rates. In a follow-up second paper we perform detailed photoionization modeling of the infrared lines in order to constrain the bolometric luminosity of the ULX
Spitzer Uncovers Active Galactic Nuclei Missed by Optical Surveys in 7 Late-type Galaxies
We report the discovery using Spitzers high resolution spectrograph of 7
Active Galactic Nuclei (AGN) in a sample of 32 late-type galaxies that show no
definitive signatures of AGN in their optical spectra. Our observations suggest
that the AGN detection rate in late-type galaxies is possibly 4 times larger
than what optical spectroscopic observations alone suggest. We demonstrate
using photoionization models with an input AGN and an extreme EUV-bright
starburst ionizing radiation field that the observed mid-infrared line ratios
cannot be replicated unless an AGN contribution, in some cases as little as 10%
of the total galaxy luminosity, is included. These models show that when the
fraction of the total luminosity due to the AGN is low, optical diagnostics are
insensitive to the presence of the AGN. In this regime of parameter space, the
mid-infrared diagnostics offer a powerful tool for uncovering AGN missed by
optical spectroscopy. The AGN bolometric luminosities in our sample range from
~3 X 10^41 - ~2 X 10^43 ergs s^-1, which, based on the Eddington limit,
corresponds to a lower mass limit for the black hole that ranges from ~3 X
10^3Mdot to as high as ~1.5 X 10^5Mdot. These lower mass limits however do not
put a strain on the well-known relationship between the black hole mass and the
host galaxy's stellar velocity dispersion established in predominantly
early-type galaxies. Our findings add to the growing evidence that black holes
do form and grow in low-bulge environments and that they are significantly more
common than optical studies indicate.Comment: 8 figures, 17 pages, astro-ph\0801.2766 (Abel & Satyapal 2008; ApJ
accepted) and this posting designed to form a two-part investigatio
The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX
This is the second of two papers examining Spitzer Infrared Spectrograph
(IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here
we perform detailed photoionization modeling of the infrared lines. Our
analysis suggests that the luminosity and morphology of the [O IV] 25.89 m
emission line is consistent with photoionization by the soft X-ray and far
ultraviolet (FUV) radiation from the accretion disk of the binary system and
inconsistent with narrow beaming. We show that the emission nebula is
matter-bounded both in the line of sight direction and to the east, and
probably radiation-bounded to the west. A bolometric luminosity in excess of
10 erg s would be needed to produce the measured [O IV] flux. We
use modeling and previously published studies to conclude that shocks likely
contribute very little, if at all, to the high-ionization line fluxes observed
in the Holmberg II ULX. Additionally, we find that the spectral type of the
companion star has a surprisingly strong effect on the predicted strength of
the [O IV] emission. This finding could explain the origin of [O IV] in some
starburst systems containing black hole binaries.Comment: Accepted by Ap
Pemanfaatan Teknologi Pembangkit Listrik Hybrid Pada Peternakan Ayam Desa Sukonolo Kabupaten Malang
Our lives are now so dependent on electricity. Loss of electricity could cause our lives could not walk normally. Various aspects of life becomes blocked, either from our daily lives to efforts that require electrical energy. The high cost of electricity tariff barriers add to the long facing entrepreneurs. Chicken farm is one of the types of businesses that require a constant electrical energy, in case of rolling blackouts it will directly affect the production process. In addition, the location of the chicken farm that is usually placed at distant places, also very influential on the continuous supply of electrical energy. Hybrid power plant technology is the right solution to respond all these problems. The plant can harness the energy that is around us, such as wind and sunlight. Then make it a stable supply of electrical energy, constant, and environment friendly. Hybrid plant is capable of producing electrical energy 12 kWh / day while the partner needs to reach 5.31 kWh / day and a chicken farmer can save electricity cost of Rp. 173,600 / month. With the results of the application of Hybrid Generating proven to reduce production costs by utilizing renewable energy on a chicken farm village Sukonolo Malang, so that energy independence can be achieved
Spitzer Observations of MF 16 Nebula and the associated Ultraluminous X-ray Source
We present Spitzer Infrared Spectrograph (IRS) observations of the
ultra-luminous X-ray source (ULX) NGC 6946 X-1 and its associated nebula MF 16.
This ULX has very similar properties to the famous Holmberg II ULX, the first
ULX to show a prominent infrared [O IV] emission line comparable to those found
in AGN. This paper attempts to constrain the ULX Spectral Energy Distribution
(SED) given the optical/UV photometric fluxes and high-resolution X-ray
observations. Specifically, Chandra X-ray data and published Hubble optical/UV
data are extrapolated to produce a model for the full optical to X-ray SED. The
photoionization modeling of the IR lines and ratios is then used to test
different accretion spectral models. While either an irradiated disk model or
an O-supergiant plus accretion disk model fit the data very well, we prefer the
latter because it fits the nebular parameters slightly better. In this second
case the accretion disk alone dominates the extreme-UV and X-ray emission,
while an O-supergiant is responsible for most of the far-UV emission.Comment: 26 pages, 7 figures, accepted by Ap
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