scholarly journals IMF-induced intrinsic uncertainties on measuring galaxy distances based on the number of giant stars: the case of the ultradiffuse galaxy NGC 1052-DF2

2021 ◽  
Vol 504 (2) ◽  
pp. 1668-1675
Author(s):  
Akram Hasani Zonoozi ◽  
Hosein Haghi ◽  
Pavel Kroupa
Keyword(s):  
Surface Brightness ◽  
Distance Estimation ◽  
Star Formation History ◽  
Giant Stars ◽  
Formation History ◽  
Low Surface Brightness ◽  
Brightness Fluctuation ◽  
Low Mass ◽  
Natural Result ◽  
Mass Functions

ABSTRACT The surface brightness fluctuation (SBF) technique is one of the distance measurement methods that has been applied on the low surface brightness (LSB) galaxy NGC 1052-DF2 yielding a distance of about 20 Mpc implying it to be a dark matter deficient galaxy. We assume the number of giant stars above a given luminosity threshold to represent the SBF magnitude. The SBF magnitude depends on the distance, but this is degenerate with the star formation history (SFH). Using a stellar population synthesis model, we calculate the number of giant stars for stellar populations with different galaxy-wide stellar initial mass functions (gwIMFs), ages, metallicities, and SFHs. If the gwIMF is the invariant canonical IMF, the 1σ (3σ) uncertainty in colour allows a distance as low as 12 Mpc (8 Mpc). If instead the true underlying gwIMF is the integrated galaxy-wide IMF (IGIMF) then overestimating distances for low-mass galaxies would be a natural result, allowing NGC 1052-DF2 to have a distance of 11 Mpc within the 1σ colour uncertainty. Finally, we show that our main conclusion on the existence of a bias in the SBF distance estimation is not much affected by changing the luminosity lower limit for counting giant stars.

scholarly journals Photometric Structure and Star Formation in Blue Compact Dwarf Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 327-327
Author(s):  
P. Papaderos
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Host Galaxy ◽  
Star Forming ◽  
Formation History ◽  
Low Surface Brightness ◽  
Low Mass

The star-formation history and chemodynamical evolution of Blue Compact Dwarf (BCD) galaxies are central issues in dwarf galaxy research. In spite of being old in their vast majority, BCDs resemble in many aspects unevolved low-mass galaxies in the early universe. They are gas-rich (Hi mass fraction of typically > 30%) and metal-deficient (7.1 $\la$ 12+log(O/H) $\la$ 8.3) extragalactic systems, undergoing intense star-forming (SF) activity within an underlying low-surface brightness (LSB) host galaxy.

scholarly journals How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

2020 ◽  
Vol 501 (2) ◽  
pp. 1568-1590
Author(s):  
Lukas J Furtak ◽  
Hakim Atek ◽  
Matthew D Lehnert ◽  
Jacopo Chevallard ◽  
Stéphane Charlot
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Stellar Mass ◽  
Star Formation History ◽  
Space Telescope ◽  
Formation History ◽  
Low Mass ◽  
Stellar Masses ◽  
Dust Attenuation ◽  
The Impact

ABSTRACT We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer/IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to $M_{\star }\gt 10^{6}\, \text{M}_{\odot}$ and we find the z ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope $\alpha \simeq -1.96_{-0.08}^{+0.09}$ and a turnover at $\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$ with a curvature of $\beta \simeq 1.00_{-0.73}^{+0.87}$ for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV ≤ 0.2. We find that the z ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from $\alpha \simeq -1.82_{-0.07}^{+0.08}$ for an exponentially rising SFH to $\alpha \simeq -2.34_{-0.10}^{+0.11}$ when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF.

scholarly journals Studies of the Planetary Nebulae in NGC 5128

2003 ◽  
Vol 209 ◽  
pp. 593-593
Author(s):  
J. R. Walsh ◽  
G. H. Jacoby ◽  
R. F. Peletier ◽  
N. A. Walton
Keyword(s):  
Planetary Nebula ◽  
Surface Density ◽  
Stellar Population ◽  
Elliptical Galaxy ◽  
Small Distance ◽  
Star Formation History ◽  
Stellar Photometry ◽  
Element Abundances ◽  
Formation History ◽  
Low Mass

As the nearest large elliptical galaxy, NGC 5128 is ideal for planetary nebula studies. Its size, favourable aspect, small distance and reddening allow low mass stellar evolution in a whole galaxy to be surveyed. The surface density and properties of the PN can be compared with stars of various ages, metallicities and components (bulge, halo). The PN provide the α-element abundances whilst stellar photometry is calibrated against Fe/H; applied to the same stellar population, the PN abundances can be related to those of the stars. Gradients and non-radial trends in the abundance can be mapped using spectral observations of a large number of PN, allowing star formation history to be studied.

scholarly journals Stellar Over-Densities in the Outer Halo of the Milky Way

2010 ◽  
Vol 27 (1) ◽  
pp. 45-55 ◽  
Author(s):  
Stefan C. Keller
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Local Density ◽  
Spatial Scales ◽  
Sloan Digital Sky Survey ◽  
Tidal Disruption ◽  
Giant Stars ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Model Predictions

AbstractThis study presents a tomographic survey of a subset of the outer halo (10–40 kpc) drawn from the Sloan Digital Sky Survey Data Release 6. Halo substructure on spatial scales of >3 degrees is revealed as an excess in the local density of sub-giant stars. With an appropriate assumption of a model stellar isochrone it is possible for us to then derive distances to the sub-giant population. We describe three new candidate halo substructures; the 160- and 180-degree over-densities (at distances of 17 and 19 kpc respectively and radii of 1.3 and 1.5 kpc respectively) and an extended feature at 28 kpc that covers at least 162 deg2, the Virgo Equatorial Stream. In addition, we recover the Sagittarius dwarf galaxy (Sgr) leading-arm material and the Virgo Over-Density.The derived distances, together with the number of sub-giant stars associated with each substructure, enables us to derive the integrated luminosity for the features. The tenuous, low surface brightness of the features strongly suggests an origin from the tidal disruption of an accreted galaxy or galaxies. Given the dominance of the tidal debris of Sgr in this region of the sky we investigate if our observations can be accommodated by tidal disruption models for Sgr. The clear discordance between observations and model predictions for known Sgr features means it is difficult to tell unambiguously if the new substructures are related to Sgr or not. Radial velocities in the stellar over-densities will be critical in establishing their origins.

Isolated dwarf galaxies in the Local Group

2018 ◽  
Vol 14 (S344) ◽  
pp. 81-85
Author(s):  
Clare R. Higgs ◽  
Alan W. McConnachie ◽  
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Apparent Size ◽  
Stellar Structure ◽  
Star Formation History ◽  
Wide Field ◽  
Formation History ◽  
Close Proximity ◽  
Low Mass

AbstractThe Solo (Solitary local) Dwarf Galaxy Survey is a volume limited sample of all nearby (< 3 Mpc) and isolated (> 300 kpc from the Milky Way or M31) dwarfs, with wide-field g and i imaging. This survey uses resolved stellar populations to parameterize these low mass systems. Comparison to the well studied satellite dwarfs characterizes the evolutionary impact of a large galaxy in close proximity. The deep, wide field nature of this survey also lends itself to searching for nearby substructures, both globular clusters and possible faint satellites.Current work is focused on the 16 closest Solo dwarfs, all within the virial radius (approximately 1 Mpc) of the Local Group. This subset has been characterized using consistent methods, despite their diversity in stellar mass and apparent size. The analysis highlights the extended stellar structure and morphology. We will examine trends with star formation history, and separation from a large host. This first subset emphasizes the survey’s unique challenges and advantages.The Solo Survey provides detailed look at the extended structure of dwarfs and characterizes the evolution of galaxies in the faint limit.

scholarly journals Dwarf Galaxies: From the Epoch of Peak Star Formation to the Epoch of Reionization

2018 ◽  
Vol 14 (S344) ◽  
pp. 429-436
Author(s):  
Hakim Atek
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Great Part ◽  
Star Formation History ◽  
Dark Matter Halos ◽  
Galaxy Surveys ◽  
Formation History ◽  
History Of ◽  
Low Mass

AbstractDwarf galaxies represent the dominant population at high redshift and they most likely contributed in great part to star formation history of the Universe and cosmic reionization. The importance of dwarf galaxies at high redshift has been mostly recognized in the last decade due to large progress in observing facilities allowing deep galaxy surveys to identify low-mass galaxies. This population appear to have extreme emission lines and ionizing properties that challenge stellar population models. Star formation follows a stochastic process in these galaxies, which has important implication on the ionizing photon production and its escape fraction whose measurements are challenging for both simulations and observations. Outstanding questions include: what are the physical properties at the origin of such extreme properties? What are the smallest dark matter halos that host star formation? Are dwarf galaxies responsible for cosmic reionization?

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