54 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
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
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
The properties of dwarf spheroidal galaxies in the Cen A group
Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the Local Group, but their low luminosity and surface brightness make similar work in more distant galaxy groups challenging. Modern instrumentation unlocks the possibility of scrutinizing these faint systems in other environments, expanding the parameter space of group properties. We use MUSE spectroscopy to study the properties of 14 known or suspected dSph satellites of Cen A. Twelve targets are confirmed to be group members based on their radial velocities. Two targets are background galaxies at ∼50 Mpc: KK 198 is a face-on spiral galaxy, and dw1315−45 is an ultra-diffuse galaxy with an effective radius of ∼2300 pc. The 12 confirmed dSph members of the Cen A group have old and metal-poor stellar populations and follow the stellar metallicity-luminosity relation defined by the dwarf galaxies in the Local Group. In the three brightest dwarf galaxies (KK 197, KKs 55, and KKs 58), we identify globular clusters, as well as a planetary nebula in KK 197, although its association with this galaxy and/or the extended halo of Cen A is uncertain. Using four discrete tracers, we measure the velocity dispersion and dynamical mass of KK 197. This dSph appears dark matter dominated and lies on the radial acceleration relation of star-forming galaxies within the uncertainties. It also is consistent with predictions stemming from modified Newtonian dynamics. Surprisingly, in the dwarf KK 203 we find an extended Hα ring. Careful examination of Hubble Space Telescope photometry reveals a very low level of star formation at ages between 30 and 300 Myr. The Hα emission is most likely linked to a ∼40 Myr old supernova remnant, although other possibilities for its origin cannot be entirely ruled out
Cosmicflows-4
With Cosmicflows-4, distances are compiled for 55,877 galaxies gathered into
38,065 groups. Eight methodologies are employed, with the largest numbers
coming from the correlations between the photometric and kinematic properties
of spiral galaxies (TF) and elliptical galaxies (FP). Supernovae that arise
from degenerate progenitors (SNIa) are an important overlapping component.
Smaller contributions come from distance estimates from the surface brightness
fluctuations of elliptical galaxies (SBF) and the luminosities and expansion
rates of core collapse supernovae (SNII). Cepheid Period-Luminosity Relation
(CPLR) and Tip of the Red Giant Branch (TRGB) observations founded on local
stellar parallax measurements along with the geometric maser distance to NGC
4258 provide the absolute scaling of distances. The assembly of galaxies into
groups is an important feature of the study in facilitating overlaps between
methodologies. Merging between multiple contributions within a methodology and
between methodologies is carried out with Bayesian Markov chain Monte Carlo
procedures. The final assembly of distances is compatible with a value of the
Hubble constant of km s Mpc with the small statistical
error km s Mpc but a large potential systematic error
~3 km s Mpc. Peculiar velocities can be inferred from the
measured distances. The interpretation of the field of peculiar velocities is
complex because of large errors on individual components and invites analyses
beyond the scope of this study.Comment: 38 pages, 24 figures. catalogs available at edd.ifa.hawaii.edu.
Accepted to Ap
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