299 research outputs found
The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks
Observations of HO masers from circumnuclear disks in active galaxies for
the Megamaser Cosmology Project allow accurate measurement of the mass of
supermassive black holes (BH) in these galaxies. We present the Very Long
Baseline Interferometry (VLBI) images and kinematics of water maser emission in
six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388,
NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six
megamaser galaxies, plus a seventh previously published, to determine accurate
enclosed masses within the central pc of these galaxies, smaller than
the radius of the sphere of influence of the central mass in all cases. We also
set lower limits to the central mass densities of between 0.12 and 60 ~pc. For six of the seven disks, the high central
densities rule out clusters of stars or stellar remnants as the central
objects, and this result further supports our assumption that the enclosed mass
can be attributed predominantly to a supermassive black hole. The seven BHs
have masses ranging between 0.76 and 6.510. The BH mass
errors are \%, dominated by the uncertainty of the Hubble constant.
We compare the megamaser BH mass determination with other BH mass measurement
techniques. The BH mass based on virial estimation in four galaxies is
consistent with the megamaser BH mass given the latest empirical value of
, but the virial mass uncertainty is much greater. MCP
observations continue and we expect to obtain more maser BH masses in the
future.Comment: 18 pages, 4 figures. This paper has been submitted to ApJ. An updated
version of this paper will be posted when it gets accepte
A search for signatures of interactions of X-ray binary outflows with their environments with ALMA
We observed the X-ray binaries CirX-1, ScoX-1, GRS 1915+105, GX13+1, and
CygX-1 with the Atacama Large Millimeter/submillimeter Array (ALMA). Unresolved
continuum emission is found at the positions of all the sources at a frequency
of 92 GHz, with flux densities ranging between 0.8 and 10 mJy/beam. In all
cases the emission can be associated with jets that have been extensively
observed at lower frequencies. We searched for line emission from H
recombination, SiO,H2O, and CH3OH at the positions of all the sources and, for
CirX-1 and CygX-1, also at regions where shocks associated with an interaction
between the jet and the interstellar medium had previously been observed. The
search did not yield any significant detection, resulting in 3 upper
limits between 0.65 and 3.7 K km s for the existence of line emission in
these regions. In contrast, we detected spatially unresolved SiO emission in
the field of view of GX13+1, and we tentatively associate this emission with a
SiO maser in a potential young stellar object or evolved star. We also found
spatially extended line emission at two additional sites in the field of view
of GX13+1 that we tentatively associate with emission from SO and CH3OH; we
speculate that it may be associated with a star-forming region, but again we
cannot rule out alternative origins such as emission from evolved stars.Comment: Accepted for publication in A&
The Megamaser Cosmology Project. X. High Resolution Maps and Mass Constraint for SMBHs
We present high resolution (sub-mas) VLBI maps of nuclear H2O megamasers for
seven galaxies. In UGC6093, the well-aligned systemic masers and high-velocity
masers originate in an edge-on, flat disk and we determine the mass of the
central SMBH to be M_SMBH = 2.58*10^7Msun(+-7%). For J1346+5228, the
distribution of masers is consistent with a disk, but the faint high-velocity
masers are only marginally detected, and we constrain the mass of the SMBH to
be in the range 1.5-2.0*10^7Msun. The origin of the masers in Mrk1210 is less
clear, as the systemic and high-velocity masers are misaligned and show a
disorganized velocity structure. We present one possible model in which the
masers originate in a tilted, warped disk, but we do not rule out the
possibility of other explanations including outflow masers. In NGC6926, we
detect a set of redshifted masers, clustered within a pc of each other, and a
single blueshifted maser about 4.4pc away, an offset that would be unusually
large for a maser disk system. Nevertheless, if it is a disk system, we
estimate the enclosed mass to be M_SMBH<4.8*10^7 Msun . For NGC5793, we detect
redshifted masers spaced about 1.4pc from a clustered set of blueshifted
features. The orientation of the structure supports a disk scenario as
suggested by Hagiwara et al.(2001). We estimate the enclosed mass to be M
SMBH<1.3*10^7 Msun. For NGC2824 and J0350-0127, the masers may be associated
with pc or sub-pc scale jets or outflows.Comment: Accepted by Ap
Radio continuum of galaxies with HO megamaser disks: 33 GHz VLA data
We investigate the nuclear environment of galaxies with observed 22 GHz water
megamaser in their subparsec edge-on accretion disks, using 33 GHz (9mm) radio
continuum data from VLA, with a resolution of ~ 0.2-0.5 arcsecs, and relate the
maser and host galaxy properties to those of its radio continuum emission.
Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio
continuum emission at levels of 4.5-240 . Five sources show extended
emission, including one source with two main components and one with three main
components. The remaining detected 16 sources exhibit compact cores within the
sensitivity limits. Little evidence is found for extended jets (>300 pc) in
most sources. Either they do not exist, or our chosen frequency of 33 GHz is
too high for a detection of these supposedly steep spectrum features. In only
one source among those with known maser disk orientation, NGC4388, we found an
extended jet-like feature that appears to be oriented perpendicular to the
water megamaser disk. Smaller 100-300 pc sized jets might also be present, as
is suggested by the beam-deconvolved morphology of our sources. Whenever
possible, central positions with accuracies of 20-280 mas are provided. A
correlation analysis shows that the 33 GHz luminosity weakly correlates with
the infrared luminosity. The 33 GHz luminosity is anticorrelated with the
circular velocity of the galaxy. The black hole masses show stronger
correlations with water maser luminosity than with 1.4 GHz, 33 GHz, or hard
X-ray luminosities. Furthermore, the inner radii of the disks show stronger
correlations with 1.4 GHz, 33 GHz, and hard X-ray luminosities than their outer
radii, suggesting that the outer radii may be affected by disk warping, star
formation, or peculiar density distributions.Comment: 18 pages, 10 figures, Accepted for publication in A&
ALLSMOG: an APEX Low-redshift Legacy Survey for MOlecular Gas. I - molecular gas scaling relations, and the effect of the CO/H2 conversion factor
We present ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas.
ALLSMOG is a survey designed to observe the CO(2-1) emission line with the APEX
telescope, in a sample of local galaxies (0.01 < z < 0.03), with stellar masses
in the range 8.5 < log(M*/Msun) < 10. This paper is a data release and initial
analysis of the first two semesters of observations, consisting of 42 galaxies
observed in CO(2-1). By combining these new CO(2-1) emission line data with
archival HI data and SDSS optical spectroscopy, we compile a sample of low-mass
galaxies with well defined molecular gas masses, atomic gas masses, and
gas-phase metallicities. We explore scaling relations of gas fraction and gas
consumption timescale, and test the extent to which our findings are dependent
on a varying CO/H2 conversion factor. We find an increase in the H2/HI mass
ratio with stellar mass which closely matches semi-analytic predictions. We
find a mean molecular gas fraction for ALLSMOG galaxies of MH2/M* = (0.09 -
0.13), which decreases with stellar mass. We measure a mean molecular gas
consumption timescale for ALLSMOG galaxies of 0.4 - 0.7 Gyr. We also confirm
the non-universality of the molecular gas consumption timescale, which varies
(with stellar mass) from ~100 Myr to ~2 Gyr. Importantly, we find that the
trends in the H2/HI mass ratio, gas fraction, and the non-universal molecular
gas consumption timescale are all robust to a range of recent
metallicity-dependent CO/H2 conversion factors.Comment: 25 pages, 15 figures. Accepted for publication in MNRA
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