68 research outputs found
Distance and mass of the M104 (Sombrero) group
Distances and radial velocities of galaxies in the vicinity of the luminous
early-type galaxy M 104 (Sombrero) are used to derive its dark matter mass.
Two dwarf galaxies: UGCA 307 and KKSG 30 situated near M 104 were observed
with the Advanced Camera for Surveys on the Hubble Space Telescope. The
distances Mpc (UGCA 307) and Mpc
(KKSG 30) were determined using the tip of the red giant branch method. These
distances are consistent with the dwarf galaxies being satellites of Sombrero.
Using radial velocities and projected separations of UGCA 307, KKSG 30, and a
third galaxy with an accurate distance (KKSG 29), as well as 12 other assumed
companions with less accurate distances, the total mass of M 104 is estimated
to be . At the K-band luminosity of the
Sombrero galaxy of , its total mass-to-luminosity ratio
is , which is about three times higher
than that of luminous bulgeless galaxies.Comment: 6 pages, 5 figures, 3 tables, accepted to Astronomy & Astrophysic
KKH 22, the first dwarf spheroidal satellite of IC 342
We present observations with the Advanced Camera for Surveys on the Hubble
Space Telescope of the nearby dwarf spheroidal galaxy KKH 22 = LEDA 2807114 in
the vicinity of the massive spiral galaxy IC 342. We derived its distance of
3.12+-0.19 Mpc using the tip of red giant branch (TRGB) method. We also used
the 6 m BTA spectroscopy to measure a heliocentric radial velocity of the
globular cluster in KKH22 to be +30+-10 km/s. The dSph galaxy KKH 22 has the
V-band absolute magnitude of -12.19 mag and the central surface brightness
mu_v,0 = 24.1 mag/sq.arcsec. Both the velocity and the distance of KKH 22 are
consistent with the dSph galaxy being gravitationally bound to IC 342. Another
nearby dIr galaxy, KKH 34, with a low heliocentric velocity of +106 km/s has
the TRGB distance of 7.28+-0.36 Mpc residing in the background with respect to
the IC 342 group. KKH 34 has a surprisingly high negative peculiar velocity of
-236+-26 km/s.Comment: 7 pages, 6 figures, accepted in A&
Standardized Luminosity of the Tip of the Red Giant Branch utilizing Multiple Fields in NGC 4258 and the CATs Algorithm
The Tip of the Red Giant Branch provides a luminous standard candle for
calibrating distance ladders that reach Type Ia supernova (SN Ia) hosts.
However, recent work reveals that tip measurements vary at the 0.1 mag
level for different stellar populations and locations within a host, which may
lead to inconsistencies along the distance ladder. We pursue a calibration of
the tip using 11 Hubble Space Telescope fields around the maser host, NGC 4258,
that is consistent with SN Ia hosts by standardizing tip measurements via their
contrast ratios. We find -band tips that exhibit a full 0.3 mag range
and 0.1 mag dispersion. We do not find any correlation between HI column
density and the apparent tip to 0.04 0.03 mag/cm. We search for a
tip-contrast relation (TCR) and measure the TCR within the fields of NGC 4258
of mag/, where is the contrast ratio. This value is
consistent with the TCR originally discovered in the GHOSTS sample (Wu et al.
2022) of mag/R. Combining these measurements, we find a global
TCR of mag/R and a calibration of mag. We also use stellar models to simulate single
age and metallicity stellar populations with [Fe/H] from to and
ages from 3 Gyr to 12 Gyr and reconstruct the global TCR found here to a factor
of 2. This work is combined in a companion analysis with tip
measurements of nearby SN Ia hosts to measure .Comment: 20 pages, 12 figures, 3 tables. Submitted to Ap
A nearby isolated dwarf: star formation and structure of ESO 006-001
Observations with the Hubble Space Telescope unexpectedly revealed that the
dwarf galaxy ESO 006-001 is a near neighbor to the Local Group at a distance of
2.70 +- 0.11 Mpc. The stellar population in the galaxy is well resolved into
individual stars to a limit of M I ~ -0.5 mag. The dominant population is older
than 12 Gyr yet displays a significant range in metallicity of -2 < [Fe/H] <
-1, as evidenced by a Red Giant Branch with substantial width. Superimposed on
the dominant population are stars on the Main Sequence with ages less than 100
Myr and Helium burning Blue Loop stars with ages of several hundred Myr. ESO
006-001 is an example of a transition dwarf; a galaxy dominated by old stars
but one that has experienced limited recent star formation in a swath near the
center. No H i gas is detected at the location of the optical galaxy in spite
of the evidence for young stars. Intriguingly, an H i cloud with a similar
redshift is detected 9 kpc away in projection. Otherwise, ESO 006-001 is a
galaxy in isolation with its nearest known neighbor IC 3104, itself a dwarf, at
a distance of ~ 500 kpc.Comment: 13 pages, 9 figures, accepted at Ap
Quantity of Vaccine Poliovirus Shed Determines the Titer of the Serum Neutralizing Antibody Response in Indian Children Who Received Oral Vaccine
Replication of oral poliovirus vaccine (OPV) in the intestine (ie, vaccine take) is associated with seroconversion and protection against poliomyelitis. We used quantitative polymerase chain reaction analysis to measure vaccine shedding in 300 seronegative infants aged 6–11 months and in 218 children aged 1–4 years 7 days after administration of monovalent or bivalent OPV. We found that the quantity of shedding correlated with the magnitude of the serum neutralizing antibody response measured 21 or 28 days after vaccination. This suggests that the immune response to OPV is on a continuum, rather than an all-or-nothing phenomenon, that depends on efficient vaccine virus replication
Comparison of culture, single and multiplex real-time PCR for detection of Sabin poliovirus shedding in recently vaccinated Indian children
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