The ROTSE-IIIa telescope at Siding Spring Observatory, Australia, detected prompt optical emission from Swift GRB 050401. We present observations of the early optical afterglow, first detected by the ...ROTSE-IIIa telescope 33 s after the start of g-ray emission, contemporaneous with the brightest peak of this emission. This GRB was neither exceptionally long nor bright. This is the first prompt optical detection of a GRB of typical duration and luminosity. We find that the early afterglow decay does not deviate significantly from the power-law decay observable at later times and is uncorrelated with the prompt g-ray emission. We compare this detection with the other two GRBs with prompt observations, GRB 990123 and GRB 041219a. All three bursts exhibit quite different behavior at early times.
ABSTRACT We present new molecular gas maps of NGC 5195 (alternatively known as M51b) from the Combined Array for Research in Millimeter Astronomy, including 12CO(1-0), 13CO(1-0), CN(1 - ), CS(2-1), ...and 3 mm continuum. We also detected HCN(1-0) and HCO+(1-0) using the Onsala Space Observatory. NGC 5195 has a 12CO/13CO ratio ( = 11.4 0.5) consistent with normal star-forming galaxies. The CN(1-0) intensity is higher than is seen in an average star-forming galaxy, possibly enhanced in the diffuse gas in photo-dissociation regions. Stellar template fitting of the nuclear spectrum of NGC 5195 shows two stellar populations: an 80% mass fraction of old ( 10 Gyr) and a 20% mass fraction of intermediate-aged ( 1 Gyr) stellar populations. This provides a constraint on the timescale over which NGC 5195 experienced enhanced star formation during its interaction with M51a. The average molecular gas depletion timescale in NGC 5195 is = 3.08 Gyr, a factor of larger than the depletion timescales in nearby star-forming galaxies, but consistent with the depletion seen in CO-detected early-type galaxies. While radio continuum emission at centimeter and millimeter wavelengths is present in the vicinity of the nucleus of NGC 5195, we find it is most likely associated with nuclear star formation rather than radio-loud AGN activity. Thus, despite having a substantial interaction with M51a ∼1/2 Gyr ago, the molecular gas in NGC 5195 has resettled and is currently forming stars at an efficiency consistent with settled early-type galaxies.
High-resolution (0.″03–0.″09 (9–26 pc)) ALMA (100–350 GHz (
λ
3 to 0.8 mm)) and (0.″04 (11 pc)) VLA 45 GHz measurements have been used to image continuum and spectral line emission from the ...inner (100 pc) region of the nearby infrared luminous galaxy IC 860. We detect compact (
r
∼ 10 pc), luminous, 3 to 0.8 mm continuum emission in the core of IC 860, with brightness temperatures
T
B
> 160 K. The 45 GHz continuum is equally compact but significantly fainter in flux. We suggest that the 3 to 0.8 mm continuum emerges from hot dust with radius
r
∼ 8 pc and temperature
T
d
∼ 280 K, and that it is opaque at millimetre wavelengths, implying a very large H
2
column density
N
(H
2
)≳10
26
cm
−2
. Vibrationally excited lines of HCN
ν
2
= 1f
J
= 4 − 3 and 3–2 (HCN-VIB) are seen in emission and spatially resolved on scales of 40–50 pc. The line-to-continuum ratio drops towards the inner
r
= 4 pc, resulting in a ring-like morphology. This may be due to high opacities and matching HCN-VIB excitation- and continuum temperatures. The HCN-VIB emission reveals a north–south nuclear velocity gradient with projected rotation velocities of
ν
= 100 km s
−1
at
r
= 10 pc. The brightest emission is oriented perpendicular to the velocity gradient, with a peak HCN-VIB 3–2
T
B
of 115 K (above the continuum). Vibrational ground-state lines of HCN 3–2 and 4–3, HC
15
N 4–3, HCO
+
3–2 and 4–3, and CS 7–6 show complex line absorption and emission features towards the dusty nucleus. Redshifted, reversed P-Cygni profiles are seen for HCN and HCO
+
consistent with gas inflow with
ν
in
≲ 50 km s
−1
. Foreground absorption structures outline the flow, and can be traced from the north-east into the nucleus. In contrast, CS 7–6 has blueshifted line profiles with line wings extending out to −180 km s
−1
. We suggest that a dense and slow outflow is hidden behind a foreground layer of obscuring, inflowing gas. The centre of IC 860 is in a phase of rapid evolution where an inflow is building up a massive nuclear column density of gas and dust that feeds star formation and/or AGN activity. The slow, dense outflow may be signaling the onset of feedback. The inner,
r
= 10 pc, IR luminosity may be powered by an AGN or a compact starburst, which then would likely require a top-heavy initial mass function.
We present the results of a search for untriggered gamma-ray burst (GRB) afterglows with the Robotic Optical Transient Search Experiment-III (ROTSE-III) telescope array. This search covers ...observations from 2003 September to 2005 March. We have an effective coverage of 1.74 deg super(2) yr for rapidly fading transients that remain brighter than 617.5 mag for more than 30 minutes. This search is the first large-area survey to be able to detect typical untriggered GRB afterglows. Our background rate is very low and purely astrophysical. We have found four previously unknown cataclysmic variables (CVs) and one new flare star. We have not detected any candidate afterglow events or other unidentified transients. We can place an upper limit on the rate of fading optical transients with quiescent counterparts dimmer than 620th magnitude at a rate of less than 1.9 deg super(-2) yr super(-1) with 95% confidence. This places limits on the optical characteristics of off-axis (orphan) GRB afterglows. As a by-product of this search, we have an effective 652 deg super(2) yr of coverage for very slowly decaying transients, such as CVs. This implies an overall rate of outbursts from high Galactic latitude CVs of 0.1 deg super(-2) yr super(-1).
We present the unfiltered ROTSE-III light curve of the optical transient associated with GRB 050319 beginning 4 s after the cessation of g-ray activity. We fit a power-law function to the data using ...the revised trigger time given by Chincarini and coworkers, and a smoothly broken power-law to the data using the original trigger disseminated through the GCN notices. Including the RAPTOR data from Wo zniak and coworkers, the best-fit power-law indices are a = -0.854 c 0.014 for the single power-law and a sub(1) = -0.364 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(2) sub(1) super(0) sub(9), a sub(2) = -0.881 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(3) sub(3) super(0) sub(1), with a break at t sub(b) = 418 super(+) sub(-) super(3) sub(3) super(1) sub(0) s for the smoothly broken fit. We discuss the fit results, with emphasis placed on the importance of knowing the true start time of the optical transient for this multipeaked burst. As Swift continues to provide prompt GRB locations, it becomes more important to answer the question, "when does the afterglow begin?" in order to correctly interpret the light curves.
Abstract
We map for the first time the two-dimensional H
2
excitation of warm intergalactic gas in Stephan's Quintet on group-wide (50 × 35 kpc
2
) scales to quantify the temperature, mass, and warm ...H
2
mass fraction as a function of position using
Spitzer
. Molecular gas temperatures are seen to rise (to
T
> 700 K) and the slope of the power-law density–temperature relation flattens along the main ridge of the filament, defining the region of maximum heating. We also performed MHD modeling of the excitation properties of the warm gas, to map the velocity structure and energy deposition rate of slow and fast molecular shocks. Slow magnetic shocks were required to explain the power radiated from the lowest-lying rotational states of H
2
, and strongly support the idea that energy cascades down to small scales and low velocities from the fast collision of NGC 7318b with group-wide gas. The highest levels of heating of the warm H
2
are strongly correlated with the large-scale stirring of the medium as measured by C
ii
spectroscopy with
Herschel
. H
2
is also seen associated with a separate bridge that extends toward the Seyfert nucleus in NGC 7319, from both
Spitzer
and CARMA CO observations. This opens up the possibility that both galaxy collisions and outflows from active galactic nuclei can turbulently heat gas on large scales in compact groups. The observations provide a laboratory for studying the effects of turbulent energy dissipation on group-wide scales, which may provide clues about the heating and cooling of gas at high
z
in early galaxy and protogalaxy formation.
We map for the first time the two-dimensional H{sub 2} excitation of warm intergalactic gas in Stephan's Quintet on group-wide (50 × 35 kpc{sup 2}) scales to quantify the temperature, mass, and warm ...H{sub 2} mass fraction as a function of position using Spitzer . Molecular gas temperatures are seen to rise (to T > 700 K) and the slope of the power-law density–temperature relation flattens along the main ridge of the filament, defining the region of maximum heating. We also performed MHD modeling of the excitation properties of the warm gas, to map the velocity structure and energy deposition rate of slow and fast molecular shocks. Slow magnetic shocks were required to explain the power radiated from the lowest-lying rotational states of H{sub 2}, and strongly support the idea that energy cascades down to small scales and low velocities from the fast collision of NGC 7318b with group-wide gas. The highest levels of heating of the warm H{sub 2} are strongly correlated with the large-scale stirring of the medium as measured by C ii spectroscopy with Herschel . H{sub 2} is also seen associated with a separate bridge that extends toward the Seyfert nucleus in NGC 7319, from both Spitzer and CARMA CO observations. This opens up the possibility that both galaxy collisions and outflows from active galactic nuclei can turbulently heat gas on large scales in compact groups. The observations provide a laboratory for studying the effects of turbulent energy dissipation on group-wide scales, which may provide clues about the heating and cooling of gas at high z in early galaxy and protogalaxy formation.
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