J/MNRAS/494/2600 Properties of immediate Milky Way's neighbours (Neuzil+, 2020)
The Sheet of Giants: Unusual properties of the Milky Way's immediate
neighbourhood.
Neuzil M.K., Mansfield P., Kravtsov A.V.
<Mon. Not. R. Astron. Soc., 494, 2600-2617 (2020)>
=2020MNRAS.494.2600N 2020MNRAS.494.2600N (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry ; Radial velocities ; Optical
Keywords: catalogues - galaxies: abundances - large-scale structure of Universe
Abstract:
We quantify the shape and overdensity of the galaxy distribution in
the 'Local Sheet' within a sphere of R=8Mpc and compare these
properties with the expectations of the ΛCDM model. We measure
ellipsoidal axis ratios of c/a∼0.16 and b/a∼0.79, indicating that the
distribution of galaxies in the Local Volume can be approximated by a
flattened oblate ellipsoid, consistent with the 'sheet'-like
configuration noted in previous studies. In contrast with previous
estimates that the Local Sheet has a density close to average, we find
that the number density of faint and bright galaxies in the Local
Volume is ∼1.7 and ∼5.2 times denser, respectively, than the mean
number density of galaxies of the same luminosity. Comparison with
simulations shows that the number density contrasts of bright and
faint galaxies within 8Mpc alone make the Local Volume a ∼2.5σ
outlier in the ΛCDM cosmology. Our results indicate that the
cosmic neighbourhood of the Milky Way may be unusual for galaxies of
similar luminosity. The impact of the peculiar properties of our
neighbourhood on the properties of the Milky Way and other nearby
galaxies is not yet understood and warrants further study.
Description:
To study the distribution of galaxies in the Local Volume, we use the
LVG (Karachentsev et al. 2013AJ....145..101K 2013AJ....145..101K, Cat. J/AJ/145/101). The
LVG is a galaxy catalogue that compiles asymptotic B- and Ks-band
magnitudes, extinction corrections, distances, and a range of other
properties for all known galaxies within 11Mpc from the Milky Way. It
is continuously updated as new galaxies are discovered.
We update the LVG catalogue by performing an additional literature
review on the brightest nearby galaxies with fiducial LVG distances
smaller than 10Mpc and fiducial LVG corrected B-band magnitudes
brighter than -15 or which did not have magnitude entries in the LVG.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 142 304 Updated LVG catalog with total magnitudes BT,
extinctions and distances from the literature
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See also:
J/AJ/145/101 : Updated nearby galaxy catalog (Karachentsev+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Galaxy name
18- 22 F5.2 mag BTmag Total Vega B-band magnitude
24- 27 F4.2 mag ABg Galactic B-band extinction
29- 32 F4.2 mag ABi ? Internal B-band extinction
34 I1 --- f_BTmag Flag indicating the method used to obtain BTmag
(1)
36- 55 A20 --- r_BTmag BibCode of the source paper for BTmag
57- 61 F5.2 mag mu Best-fitting distance modulus
63- 66 F4.2 mag e_mu ? Statistical error on mu
68- 83 A16 --- f_mu Flag indicating the method used to measure the
distance (2)
85- 88 F4.2 mag esmu ? Estimated systematic error due to a lack of
homogenization for the given distance
method (2)
90- 96 F7.4 --- nx X coordinate of the unit vector pointing from
Earth to the galaxy in supergalactic
coordinates
98- 104 F7.4 --- ny Y coordinate of the unit vector pointing from
Earth to the galaxy in supergalactic
coordinates
106- 112 F7.4 --- nz Z coordinate of the unit vector pointing from
Earth to the galaxy in supergalactic
coordinates
114- 119 F6.2 arcmin a26.5 ? Major axis of the 26.5mag/arcsec2 Holmberg
isophote of the galaxy (3)
121- 124 F4.2 --- b/a ? b/a axis ratio of the Holmberg isophote
126- 131 F6.2 km/s W50 ? 50% HI linewidth of the galaxy
133- 134 I2 --- Morph Hubble morphological index of the galaxy
136- 142 F7.2 km/s RV ? Radial velocity of the galaxy relative to the
centroid of the Local Group
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Note (1): Flag as follows:
Eclipsing Binary = Eclipsing Binary (4/304)
TRGB = Tip of the Red Giant Branch (146/304)
Cepheids = Cepheids (3/304)
SBF = Surface Brightness Fluctuations (15/304)
Tully-Fisher = Tully-Fisher (104/304)
BTF = Baryonic Tully-Fisher (4/304)
BS = Brightest Stars (5/304)
NAM = Numerical Action Method: Shaya et al. 2017ApJ...850..207S 2017ApJ...850..207S,
Cat. J/ApJ/850/207 (7/304)
Membership = Redshift-space association with a nearby galaxy (16/304)
Note (2): This estimate was only performed for Eclipsing Binary, TRGB, Cepheid,
SBF and Tully-Fisher measurements
Note (3): Some galaxies have surface brightnesses too low for this Holmberg
radius to be reliably determined. In these cases the exponential
radius is used. Extreme care should be taken in interpreting this
radius for moderate-to-low surface brightness galaxies.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 30-May-2023