Fig 8 - uploaded by Yongheng Zhao
Content may be subject to copyright.
Overdensities’ positions in galactic coordinates in Aitoff projection. The gray area encloses the main area of North Galactic Cap covered by the SDSS DR5 data. Filled circles are candidates in this paper. Plus symbols are UMa II, Willman 1, UMa I, CVn I, CVn II, Her, Leo IV, Com and Seg 1. Star symbols are globular clusters in the SDSS DR5 area we detect. The triple thin solid lines are Anticenter Stream of Grillmair 2006b which may be related to the Monoceros Ring. The thin dotted line is GD-1. The thin dashed line is Orphan stream.
Source publication
Sloan Digital Sky Survey (SDSS) DR5 photometric data with $120^{\circ} <
\alpha < 270^{\circ}$, $25^{\circ} < \delta < 70^{\circ}$ are searched for new
Milky Way companions or substructures in the Galactic halo. Five candidates are
identified as overdensities of faint stellar sources that have color-magnitude
diagrams similar to those of known glob...
Context in source publication
Similar publications
A significant proportion (∼30 per cent) of the short-duration gamma-ray bursts (SGRBs) localized by Swift have no detected host galaxy coincident with the burst location to deep limits, and also no high-likelihood association with
proximate galaxies on the sky. These SGRBs may represent a population at moderately high redshifts (z ≳ 1), for which t...
We present the discovery of three new Milky Way satellites from our search
for compact stellar overdensities in the photometric catalog of the Panoramic
Survey Telescope and Rapid Response System 1 (Pan-STARRS 1, or PS1) 3pi survey.
The first satellite, Laevens 3, is located at a heliocentric distance of
d=67+/-3 kpc. With a total magnitude of Mv=-...
The aim of this work is to study the effects of environment on the growth in
size of galaxies. We examine the stellar mass-size relation for a sample of
isolated galaxies interpreted as stellar systems where evolution has been
mainly governed by internal processes. Effects of environment on the stellar
mass-size relation are evaluated by comparing...
We present a study of the faint-end of the X-ray Luminosity Function of Low
Mass X-ray binaries in the Globular Cluster system of the cD galaxy NGC 1399 by
performing a stacking experiment on 618 X-ray undetected GCs, in order to
verify the presence of faint LMXBs and to constrain the faint-end slope of the
GC-LMXBs XLF below the individual detecti...
The distinction between globular clusters and dwarf galaxies has been progressively blurred by the recent discoveries of several
extended star clusters, with size (20–30 pc) and luminosity (−6 < Mv < −2) comparable to the one of the faint dwarf spheroidals. In order to explain their sparse structure, it has been suggested
that they formed as star c...
Citations
... Though we are not able to reproduce the literature RR Lyrae distance using their same data and calibration, we do note that the above Clementini et al. (2003) calibration is only valid for [Fe/H]> −2.1, whereas Ursa Major II is ∼ 0.4 dex more metal-poor. Other literature distances to Ursa Major II are from fitting CMDs of the very shallow discovery SDSS data, or follow up data, and report a range of distances from µ = 17.34 to µ = 17.90 (e.g., Zucker et al. 2006;Liu et al. 2008). ...
We provide uniform RR Lyrae-based distances to 39 dwarf galaxies in and around the Local Group. We determine distances based on a Bayesian hierarchical model that uses periods and magnitudes of published RR Lyrae in dwarf galaxies and is anchored to well-studied Milky Way (MW) RR Lyrae with spectroscopic metallicities and Gaia eDR3 parallaxes. Gaia eDR3 parallaxes for the anchor sample are a factor of 2, on average, more precise than DR2 parallaxes, and allow for a much better constrained period-luminosity-metallicity relation. While ~75% of our distances are within 1-$\sigma$ of recent literature RR Lyrae distances, our distances are also $\sim2$-$3$ times more precise than literature distances, on average. On average, our distances are $\sim0.05$ mag closer than literature distances, as well as $\sim0.06$ mag closer than distances derived using a theoretical period-luminosity-metallicity relation. These discrepancies are largely due to our eDR3 parallax anchor. We show that the Hipparcos-anchored RR Lyrae distance scale of Carretta et al. (2000) over-predicts distances to MW RR Lyrae by $\sim0.05$ mag. The largest uncertainties in our distances are (i) the lack of direct metallicity measurements for RR Lyrae and (ii) the heterogeneity of published RR Lyrae photometry. We provide simple formulae to place new dwarf galaxies with RR Lyrae on a common distance scale with this work. We provide public code that can easily incorporate additional galaxies and data from future surveys, providing a versatile framework for cartography of the local Universe with RR Lyrae.
... In the last decade, more faint satellite galaxies have been discovered in the Local Group (e.g. Irwin et al. 2007;Liu et al. 2008;Martin et al. 2008;Zucker et al. 2007;Watkins et al. 2009;Belokurov et al. 2010), but the number of observed satellites is still much smaller than the predicted number of subhaloes in cold dark matter simulations. To explain the problem, some studies invoke the model of warm dark matter, which predicts much less surviving small substructures (e.g. ...
We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS and SDSS around isolated central galaxies (ICGs) and galaxy pairs from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to $M_V\sim-10$, and for central primary galaxies as small as $8.5<\log_{10}M_\ast/M_\odot<9.2$ and $9.2<\log_{10}M_\ast/M_\odot<9.9$, which implies there are on average 3--8 satellites with $M_V<-10$ around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our MW, we discovered that i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; ii) there are more satellites with $-15<M_V<-10$ than those in our MW; iii) there are on average 1.5 to 2.5 satellites with $M_V<-16$ around ICGs, consistent with our MW. Thus the MW and its satellite system are atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40~Mpc in the local Universe, perhaps implying the Local Volume is an under-dense region.
... (This table is available in machine-readable form.) 53 We also examined the regions around five SDSS candidates proposed by Liu et al. (2008), but we do not find any significant excesses at these locations. ...
We report the results of a systematic search for ultra-faint Milky Way satellite galaxies using data from the Dark Energy Survey (DES) and Pan-STARRS1 (PS1). Together, DES and PS1 provide multi-band photometry in optical/near-infrared wavelengths over ~80% of the sky. Our search for satellite galaxies targets ~25,000 deg2 of the high-Galactic-latitude sky reaching a 10σ point-source depth of gsim22.5 mag in the g and r bands. While satellite galaxy searches have been performed independently on DES and PS1 before, this is the first time that a self-consistent search is performed across both data sets. We do not detect any new high-significance satellite galaxy candidates, recovering the majority of satellites previously detected in surveys of comparable depth. We characterize the sensitivity of our search using a large set of simulated satellites injected into the survey data. We use these simulations to derive both analytic and machine-learning models that accurately predict the detectability of Milky Way satellites as a function of their distance, size, luminosity, and location on the sky. To demonstrate the utility of this observational selection function, we calculate the luminosity function of Milky Way satellite galaxies, assuming that the known population of satellite galaxies is representative of the underlying distribution. We provide access to our observational selection function to facilitate comparisons with cosmological models of galaxy formation and evolution.
We provide uniform RR Lyrae-based distances to 39 dwarf galaxies in and around the Local Group. We determine distances based on a Bayesian hierarchical model that uses periods and magnitudes of published RR Lyrae in dwarf galaxies and is anchored to well-studied Milky Way (MW) RR Lyrae with spectroscopic metallicities and Gaia eDR3 parallaxes. Gaia eDR3 parallaxes for the anchor sample are a factor of 2, on average, more precise than DR2 parallaxes, and allow for a much better constrained period–luminosity–metallicity relation. While ∼75% of our distances are within 1 σ of recent RR Lyrae distances in the literature, our distances are also ∼2–3 times more precise than distances in the literature, on average. On average, our distances are ∼0.05 mag closer than distances in the literature, as well as ∼0.06 mag closer than distances derived using a theoretical period–luminosity–metallicity relation. These discrepancies are largely due to our eDR3 parallax anchor. We show that the Hipparcos-anchored RR Lyrae distance scale of Carretta et al. overpredicts distances to MW RR Lyrae by ∼0.05 mag. The largest uncertainties in our distances are (i) the lack of direct metallicity measurements for RR Lyrae and (ii) the heterogeneity of published RR Lyrae photometry. We provide simple formulae to place new dwarf galaxies with RR Lyrae on a common distance scale with this work. We provide a public code that can easily incorporate additional galaxies and data from future surveys, providing a versatile framework for the cartography of the local universe with RR Lyrae.
We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS, and SDSS around isolated central galaxies (ICGs) and paired galaxies from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to MV ∼ −10, and for central primary galaxies as small as 8.5 < log10M*/M⊙ < 9.2 and 9.2 < log10M*/M⊙ < 9.9, which implies there are on average 3–8 satellites with MV < −10 around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our Milky Way (MW), we discovered that (i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; (ii) there are on average more satellites with −15 < MV < −10 than those in our MW; (iii) there are on average 1.5 to 2.5 satellites with MV < −16 around ICGs, consistent with our MW; (iv) even after accounting for the large scatter predicted by numerical simulations, the MW satellite LF is uncommon at MV > −12. Hence, the MW and its satellite system are statistically atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40 Mpc in the local Universe, perhaps implying the Local Volume is an underdense region.
Our knowledge about the dynamics, the chemical abundances and the evolutionary histories of the more luminous dwarf spheroidal (dSph) galaxies is constantly growing. However, very little is known about the enrichment of the ultra-faint systems recently discovered in large numbers in large sky surveys. Current low-resolution spectroscopy and photometric data indicate that these galaxies are highly dark matter dominated and predominantly metal poor. On the other hand, recent high-resolution abundance analyses indicate that some dwarf galaxies experienced highly inhomogenous chemical enrichment, where star formation proceeds locally on small scales. In this article, I will review the kinematic and chemical abundance information of the Milky Way satellite dSphs that is presently available from low- and high resolution spectroscopy. Moreover, some of the most peculiar element and inhomogeneous enrichment patterns will be discussed and related to the question of to what extent the faintest dSph candidates could have contributed to the Galactic halo, compared to more luminous systems.
Recent high-resolution simulations that include Cold Dark Matter (CDM) and baryons have shown that baryonic physics can dramatically alter the dark matter structure of galaxies. These results modify our predictions for observed galaxy evolution and structure. Given these updated expectations, it is timely to re-examine observational constraints on the dark matter model. A few observations exist that may indirectly trace dark matter, and may help confirm or deny possible dark matter models. Warm Dark Matter (WDM) and Self-Interacting Dark Matter (SIDM) are currently the favorite alternative models to CDM. Constraints on the WDM particle mass require it to be so heavy that WDM is nearly indistinguishable from CDM. The best observational test of SIDM is likely to be in the dark matter distribution of faint dwarf galaxies, but there is a lack of theoretical predictions for galaxy structure in SIDM that account for the role of baryons.
The Sloan Digital Sky Survey has been immensely successful in detecting
new Milky Way satellite galaxies over the past seven years. It was
instrumental in finding examples of the least luminous galaxies we know
in the Universe, uncovering apparent inconsistencies between cold dark
matter theory and dwarf galaxy properties, providing first evidence for
a possible lower mass limit for dark matter halos in visible galaxies,
and reopening the discussion about the building block scenario for the
Milky Way halo. Nonetheless, these results are still drawn only from a
relatively small number of galaxies distributed over an area covering
about 29% of the sky, which leaves us currently with more questions than
answers. The study of these extreme stellar systems is a multi-parameter
problem: ages, metallicities, star formation histories, dark matter
contents, population fractions and spatial distributions must be
determined. Progress in the field is discussed and attention drawn to
some of the limitations that currently hamper our ability to fully
understand the phenomenon of the `ultra-faint dwarf galaxy'. In this
context, the Stromlo Milky Way Satellite Survey represents a new
initiative to systematically search and scrutinize optically elusive
Milky Way satellite galaxies in the Southern hemisphere. In doing so,
the program aims at investigating some of the challenging questions in
stellar evolution, galaxy formation and near-field cosmology.
It has been demonstrated that the inclusion of baryonic physics can alter the dark matter densities in the centers of low-mass galaxies, making the central dark matter slope more shallow than predicted in pure cold dark matter simulations. This flattening of the dark matter profile can occur in the most luminous subhalos around Milky Way mass galaxies. Zolotov et al. have suggested a correction to be applied to the central masses of dark matter-only satellites in order to mimic the affect of (1) the flattening of the dark matter cusp due to supernova feedback in luminous satellites and (2) enhanced tidal stripping due to the presence of a baryonic disk. In this paper, we apply this correction to the z = 0 subhalo masses from the high resolution, dark matter-only Via Lactea II (VL2) simulation, and find that the number of massive subhalos is dramatically reduced. After adopting a stellar mass to halo mass relationship for the VL2 halos, and identifying subhalos that are (1) likely to be destroyed by stripping and (2) likely to have star formation suppressed by photo-heating, we find that the number of massive, luminous satellites around a Milky Way mass galaxy is in agreement with the number of observed satellites around the Milky Way or M31. We conclude that baryonic processes have the potential to solve the missing satellites problem.
We introduce a new methodology to robustly determine the mass profile, as well as the overall distribution, of Local Group
satellite galaxies. Specifically, we employ a statistical multilevel modelling technique, Bayesian hierarchical modelling,
to simultaneously constrain the properties of individual Local Group Milky Way satellite galaxies and the characteristics
of the Milky Way satellite population. We show that this methodology reduces the uncertainty in individual dwarf galaxy mass
measurements up to a factor of a few for the faintest galaxies. We find that the distribution of Milky Way satellites inferred
by this analysis, with the exception of the apparent lack of high-mass haloes, is consistent with the Λ cold dark matter (ΛCDM)
paradigm. In particular, we find that both the measured relationship between the maximum circular velocity and the radius
at this velocity, as well as the inferred relationship between the mass within 300 pc and luminosity, match the values predicted
by ΛCDM simulations for haloes with maximum circular velocities below 20 km s−1. Perhaps more striking is that this analysis seems to suggest a more cusped ‘average’ halo shape that is shared by these
galaxies. While this study reconciles many of the observed properties of the Milky Way satellite distribution with that of
ΛCDM simulations, we find that there is still a deficit of satellites with maximum circular velocities of 20–40 km s−1.
