17 research outputs found
The Pedagogical Representation of Mass Functions with LEGO and their Origin
We promote the teaching of mass functions as an integral part of an
interdisciplinary science education. Mass functions characterize the frequency
distributions of objects with different masses on all cosmic scales. We intend
to enhance experiential learning of this concept with a creative LEGO brick
experiment for a diverse student audience. To our surprise, the LEGO mass
function is not only qualitatively but also quantitatively comparable to mass
functions found across the Universe. We also discuss the relation between
gravitation and mass distributions as a possible explanation for the continuity
of the universal mass function.Comment: This is the version of the article before peer review and submission.
The published version is Kautsch, Veras, & Hansotia 2021, European Journal of
Physics, 42, 035605, https://doi.org/10.1088/1361-6404/abe75
Forming Early-type Galaxies in Groups Prior to Cluster Assembly
We study a unique proto-cluster of galaxies, the supergroup SG1120-1202. We
quantify the degree to which morphological transformation of cluster galaxies
occurs prior to cluster assembly in order to explain the observed early-type
fractions in galaxy clusters at z=0. SG1120-1202 at z~0.37 is comprised of four
gravitationally bound groups that are expected to coalesce into a single
cluster by z=0. Using HST ACS observations, we compare the morphological
fractions of the supergroup galaxies to those found in a range of environments.
We find that the morphological fractions of early-type galaxies (~60 %) and the
ratio of S0 to elliptical galaxies (0.5) in SG1120-1202 are very similar to
clusters at comparable redshift, consistent with pre-processing in the group
environment playing the dominant role in establishing the observed early-type
fraction in galaxy clusters.Comment: 5 pages, 2 figures, 2 tables. Accepted for publication in ApJ Letter
A Spectroscopically Confirmed Excess of 24 micron Sources in a Super Galaxy Group at z=0.37: Enhanced Dusty Star Formation Relative to the Cluster and Field Environment
To trace how dust-obscured star formation varies with environment, we compare
the fraction of 24 micron sources in a super galaxy group to the field and a
rich galaxy cluster at z~0.35. We draw on multi-wavelength observations that
combine Hubble, Chandra, and Spitzer imaging with extensive optical
spectroscopy (>1800 redshifts) to isolate galaxies in each environment and thus
ensure a uniform analysis. We focus on the four galaxy groups in supergroup
1120-12 that will merge to form a galaxy cluster comparable in mass to Coma. We
find that 1) the fraction of supergroup galaxies with SFR(IR)>3 Msun/yr is four
times higher than in the cluster (32% vs. 7%); 2) the supergroup's infrared
luminosity function confirms that it has a higher density of IR members
compared to the cluster and includes bright IR sources not found in galaxy
clusters at z<0.35; and 3) there is a strong trend of decreasing IR fraction
with increasing galaxy density, i.e. an IR-density relation, not observed in
the cluster. These dramatic differences are surprising because the early-type
fraction in the supergroup is already as high as in clusters, i.e. the
timescales for morphological transformation cannot be strongly coupled to when
the star formation is completely quenched. The supergroup has a significant
fraction (~17%) of luminous, low-mass, IR members that are outside the group
cores (R>0.5 Mpc); once their star formation is quenched, most will evolve into
faint red galaxies. Our analysis indicates that the supergroup's 24 micron
population also differs from that in the field: 1) despite the supergroup
having twice the fraction of E/S0s as the field, the fraction of IR galaxies is
comparable in both environments, and 2) the supergroup's IR luminosity function
has a higher L(IR)* than that previously measured for the field.Comment: Accepted by the Astrophysical Journa
Roundtable 2: The Universe Explained with LEGO-Building Physics Concepts with Toy Bricks
LEGO is a versatile pedagogical tool for physical science courses. It can be used to visualize concepts qualitatively and quantitatively in physics. I will show activities using the toy bricks to promote student comprehension of abstract theories and making intellectual concepts touchable. This presentation targets all science educators.
Learning Outcomes: Use LEGO bricks to visualize science concepts Use LEGO bricks to implement hands-on student classroom activities Discuss creative teaching strategies
A search for pure disk galaxies
Flat (or superthin) galaxies are late-type edge-on spiral galaxies that exhibit large axial ratios, small stellar disk scale heights and no distinct spheroidal bulge component. This type of galaxies appears to be a pure disk system with an extended blue stellar disk embedded in a red thick layer. Flat galaxies are very common objects with low star formation rates, low metallicities, low optical surface brightness but high neutral gas fractions. Their rotation curves resemble those of dwarf and irregular galaxies. These simple disk systems offer the unique opportunity to constrain galaxy disk evolution in underevolved galaxies in the nearby Universe. They are also an evolutionary puzzle since merger scenarios do not predict the formation of pure disks. We present first results from an extensive search for flat galaxies in the Sloan Digital Sky Survey (SDSS)
A14: The Influence of Environment on the Morphological Evolution of Disk-Dominated Galaxies
Poster A14 Contribution found in citation:
Theis, C., Zeilinger, W., & Hüttemeister, S. (2005). Galaxies in Interaction. Astronomische Nachrichten, 326(7), 485-521