FIG 2 - uploaded by Sangmo Tony Sohn
Content may be subject to copyright.
-Photometric errors as a function of magnitude in our new Mosaic camera survey of the field centered on the Carina dSph.
Source publication
A new large-area Washington M, T2+DDO51 filter survey of more than 10 deg2 around the Carina dSph galaxy reveals a spectroscopically confirmed power-law radial density "break" population of Carina giant stars extending several degrees beyond the central King profile. Magellan telescope MIKE spectroscopy establishes the existence of Carina stars to...
Contexts in source publication
Context 1
... Feb 24-27 under photometric condi- tions. DAOPHOT II/ALLSTAR (Stetson 1987) PSF-fitting photometry was derived for stars in each of the individual Mo- saic pointings, producing magnitudes with median errors of (σ M , σ T2 , σ DDO51 ) = (0.018, 0.020, 0.015) at M = 20.8, which is approximately 3.4 mag below the Carina red giant branch (RGB) tip (Fig. 2). The photometry of this new survey is about 2 times more precise at that magnitude than the Carina data presented in Paper II. Instrumental magnitudes were cal- ibrated into the standard system via multiple observations of Washington+DDO51 standards in Geisler (1996). Each star in our catalog has been corrected for reddening based on ...
Context 2
... evidence for a disruption scenario is provided by the trend of velocity across the satellite. In Figure 12 we show the mean RV (in Galactic Standard of Rest) as a func- tion of b-distance from the center of Carina (approximately the major axis of the satellite). No significant RV trend in the central part of Carina that resembles a rotation curve is ob- served. ...
Context 3
... and 3b): Very few RV outliers are found among our Carina giant candidates overall, and, in ad- dition the small number of giant candidates we find that do not share the Carina dSph RV lie predominantly in the 332 km s −1 group. Furthermore, Figure 5b suggests that the outer halo is highly substructured (at least when traced by giant stars), a re- sult that is also evident from Figure 2 in Muñoz et al. (2005). In such circumstances, to obtain substantial contamination in our survey would require a considerably unfortunate conspir- acy of phenomena to produce a second halo substructure with the same RV, approximate distance, and CMD distribution as Carina; we consider this possibility as unlikely. ...
Context 4
... more metal rich (as their calcium line strengths suggest), they are also intrinsically fainter in the V band, whereas they are also brighter in apparent magnitude relative to Carina stars of the same color. All of this suggests that the moving group must be closer than Carina, and by as much as a magnitude in distance modulus or more (see, e.g., Fig. 12a of Paper I). Interest- ingly, this places the distance of these stars to be of order the distance of the Large Magellanic Cloud (LMC), the center of which not only lies only ∼ 20 • away from the center of our Ca- rina field in the sky but has a similarly high systemic heliocen- tric velocity (262 km s −1 ; van der Marel et al. (2002, ...
Similar publications
We perform a global fit within the inert doublet model taking into account experimental observables from colliders, direct and indirect dark matter searches and theoretical constraints. In particular, we consider recent results from searches for dark matter annihilation-induced gamma-rays in dwarf spheroidal galaxies and relax the assumption that t...
The dark matter density distribution in small-scale astrophysical objects may indicate that dark matter is self-interacting, while observations from clusters of galaxies suggest that the corresponding cross section depends on the velocity. Using a model-independent approach, we show that resonant self-interacting dark matter can naturally explain s...
We study the formation and evolution of the cosmic web, using the high-resolution CosmoGrid ΛCDM simulation. In particular, we investigate the evolution of the large-scale structure around void halo groups, and compare this to observations of the VGS-31 galaxy group, which consists of three interacting galaxies inside a large void.
The structure ar...
WAVES is designed to study the growth of structure, mass and energy on scales of ~1 kpc to ~10 Mpc over a 7 Gyr timeline. On the largest length scales (1-10 Mpc) WAVES will measure the structures defined by groups, filaments and voids, and their emergence over recent times. Comparisons with bespoke numerical simulations will be used to confirm, ref...
The evolution of disk galaxies in modified gravity is studied by using high-resolution N-body simulations. More specifically, we use the weak field limit of two modified gravity theories, i.e., nonlocal gravity (NLG) and scalar-tensor-vector gravity known as MOG, and ignore the existence of dark matter halo. On the other hand, we construct the same...
Citations
... Initially, the kinematic data for dSphs were limited to catalogues of line-of-sight velocities ( los ). In most cases no clear evidence of rotation was found in many dSphs (Kleyna et al. 2002;Wilkinson et al. 2004;Muñoz et al. 2005;Muñoz et al. 2006;Koch et al. 2007b,a;Walker et al. 2009), albeit for Carina, Fornax, Sculptor, Sextans, and Ursa Minor some hints of rotation based on line-of-sight velocity gradients were reported (Battaglia et al. 2008(Battaglia et al. , 2011Amorisco & Evans 2012;Fabrizio et al. 2016;Zhu et al. 2016;del Pino et al. 2017;Pace et al. 2020). However, the lack of reliable proper motion (PM) measurements did not allow clarification in most cases of whether these gradients were due to actual rotation or to projection on the sky of the PMs along the line of sight (Feast et al. 1961). ...
We present a kinematic study of a thousand of dwarf satellites of MW/M31-like hosts from the IllustrisTNG50 simulation. Internal kinematics were derived for all the snapshots to obtain a historical record of their rotation velocity in the plane of the sky ($|V_T|$) and the amplitude of their velocity gradients along the line of sight ($A_{\rm grad}^{v_z}$) measured from the host. For the majority of the satellites we initially detected rotation in the plane of the sky (65%) or velocity gradients (80%), and this was progressively reduced to 45% and 68% at $z = 0$ respectively. We find that the evolution of the rotation in the plane of the sky and the velocity gradients differs according to type of dwarfs, which could be explained in terms of their different masses and orbital histories. We observe that interaction with the host has an impact on the evolution of the internal kinematics of the satellites. The rotation signal of the satellites is progressively reduced during pericentric passages, the first pericentre being especially disruptive for the initial kinematics. We observe temporary increases in $A_{\rm grad}^{v_z}$ during pericentric passage caused by tidal interaction with the host, $A_{\rm grad}^{v_z}$ increasing as the satellites approach their pericentre and dropping as they move away. In summary, we conclude that the presence of detectable rotation in dwarf satellites is not uncommon, and that the evolution of their internal kinematics is clearly affected by their interaction with the host.
... However, all of these satellites are below the stellar mass range considered in this work. Observations have also provided evidence of extended stellar halos around classical dwarfs, such as Sculptor (Westfall et al. 2006) and Carina (Muñoz et al. 2006). All of these observations suggest that the Milky Way dwarf galaxies may be more tidally disrupted than was originally known, and motivate further searches for evidence of tidal features around known satellites. ...
We present the first detailed comparison of populations of dwarf galaxy stellar streams in cosmological simulations and the Milky Way. In particular, we compare streams identified around 13 Milky Way analogs in the FIRE-2 simulations to streams observed by the Southern Stellar Stream Spectroscopic Survey ( S ⁵ ). For an accurate comparison, we produce mock Dark Energy Survey (DES) observations of the FIRE streams and estimate the detectability of their tidal tails and progenitors. The number and stellar mass distributions of detectable stellar streams is consistent between observations and simulations. However, there are discrepancies in the distributions of pericenters and apocenters, with the detectable FIRE streams, on average, forming at larger pericenters (out to >110 kpc) and surviving only at larger apocenters (≳40 kpc) than those observed in the Milky Way. We find that the population of high-stellar-mass dwarf galaxy streams in the Milky Way is incomplete. Interestingly, a large fraction of the FIRE streams would only be detected as intact satellites in DES-like observations, since their tidal tails have too low surface brightness to be detectable. We thus predict a population of yet-undetected tidal tails around Milky Way satellites, as well as a population of fully undetected low-surface-brightness stellar streams, and estimate their detectability with the Rubin Observatory. Finally, we discuss the causes and implications of the discrepancies between the stream populations in FIRE and the Milky Way, and explore future avenues for tests of satellite disruption in cosmological simulations.
... However, all of these satellites are below the stellar mass range considered in this work. Observations have also provided evidence of extended stellar halos around classical dwarfs, such as Sculptor (Westfall et al. 2006) and Carina (Muñoz et al. 2006). All of these observations suggest that the Milky Way dwarf galaxies may be more tidally disrupted than was originally known, and motivate further searches for evidence of tidal features around known satellites. ...
We present the first detailed study comparing the populations of stellar streams in cosmological simulations to observed Milky Way dwarf galaxy streams. In particular, we compare streams identified around Milky Way analogs in the FIRE-2 simulations to stellar streams observed by the Southern Stellar Stream Spectroscopic Survey (S5). For an accurate comparison between the stream populations, we produce mock Dark Energy Survey (DES) observations of the FIRE streams and estimate the detectability of their tidal tails and progenitors. The number and stellar mass distributions of detectable stellar streams is consistent between observations and simulations. However, there are discrepancies in the distributions of pericenters and apocenters, with the detectable FIRE streams, on average, forming at larger pericenters (out to > 110 kpc) and surviving only at larger apocenters (> 40 kpc) than those observed in the Milky Way. We find that the population of high-stellar mass dwarf galaxy streams in the Milky Way is incomplete. Interestingly, a large fraction of the FIRE streams would only be detected as satellites in DES-like observations, since their tidal tails are too low-surface brightness to be detectable. We thus predict a population of yet-undetected tidal tails around Milky Way satellites, as well as a population of fully undetected low surface brightness stellar streams, and estimate their detectability with the Rubin Observatory. Finally, we discuss the causes and implications of the discrepancies between the stream populations in FIRE and the Milky Way, and explore future avenues for tests of satellite disruption in cosmological simulations.
... These have allowed the study of the internal kinematics of dSphs, providing key information about their mass profile, mass-to-light ratios and also their systemic motions. Most of these works did not find clear evidence of coherent motions within dSphs, which would explain their spheroidal shape as a consequence of a mostly pressure-supported dynamics (Kleyna et al. 2002;Wilkinson et al. 2004;Muñoz et al. 2005;Muñoz et al. 2006;Koch et al. 2007b,a;Walker et al. 2009;Wheeler et al. 2017). On the other hand, some works claim the detection of velocity gradients in the line-of-sight in Sculptor, Sextans, Fornax, and Ursa Minor (Battaglia et al. 2008b(Battaglia et al. , 2011Amorisco & Evans 2012;Zhu et al. 2016;del Pino et al. 2017a;Pace et al. 2020). ...
... • Carina: no significant evidence for rotation has been found in the inner parts of the galaxy using los in GSR with a different sample of stars (Muñoz et al. 2006). As a verification, we transform our los for Carina into GSR and proceed analogously to Section 2.3 (yet using los in GSR), looking for possible gradients. ...
... As a verification, we transform our los for Carina into GSR and proceed analogously to Section 2.3 (yet using los in GSR), looking for possible gradients. We do not find any significant gradient in los in GSR (1.24 +1.84 −1.84 km s −1 kpc −1 ), being consistent with Muñoz et al. (2006). As explained above, los in GSR can be affected by perspective effects, unlike , for which shows a clear internal velocity gradient in Carina. ...
We present a kinematic study of six dwarf spheroidal galaxies (dSph) satellites of the Milky Way (MW), namely Carina, Draco, Fornax, Sculptor, Sextans, and Ursa Minor. We combine proper motions (PMs) from the $Gaia$ Data Release 3 (DR3) and line-of-sight velocities ($v_{\mathrm{los}}$) from the literature to derive their 3D internal kinematics and to study the presence of internal velocity gradients. We find significant velocity gradients along the line-of-sight for Carina, Draco, Fornax, and Ursa Minor. The value of such gradients appears to be related to the orbital history of the dwarfs, indicating that the interaction with the Milky Way (MW) is causing them. Dwarfs that are close to the MW and moving towards their orbits pericentres show, on average, larger velocity gradients. On the other hand, dwarfs that have recently left their orbits pericentres show no significant gradients. Lastly, dwarfs located at large Galactocentric distances show gradients with an intermediate intensity. Our results would indicate that the torque caused by the strong tidal forces exerted by the MW induces a strong velocity gradient when the dwarfs approach their orbits pericentres. During the pericentre passage, the rapid change in the forces direction would disrupt such gradient, which may steadily recover as the galaxies recede. We assess our findings by analyzing dwarfs satellites from the TNG50 simulation. We find a significant increase in the intensity of the detected gradients as the satellites approach their pericentre, followed by a sharp drop as they abandon it, supporting our results for the dSphs of the MW.
... Except for Sagittarius which is an obvious case that is undergoing tidal stripping by the MW , for three of other classical ★ E-mail: yanbin.yang@obspm.fr dSphs evidence or hints of tidal-debris were found: Leo I, Carina, and UMi (Sohn et al. 2007;Muñoz et al. 2006Muñoz et al. , 2005Palma et al. 2003). Using deep photometry, Battaglia et al. (2012Battaglia et al. ( , 2013 argued that Carina could be the best candidate with tidal tail detection, but this is not confirmed by McMonigal et al. (2014). ...
... In more than two-third (7/9) of the classical dSphs, a "break" has been detected in their surface density profiles. These are Sculptor (Westfall et al. 2006), Carina (Kuhn et al. 1996;Majewski et al. 2000Majewski et al. , 2005Muñoz et al. 2006), Leo I (Sohn et al. 2007), Draco (Wilkinson et al. 2004), Sextans (Gould et al. 1992), UMi (Kocevski & Kuhn 2000;Martínez-Delgado et al. 2001;Palma et al. 2003;Muñoz et al. 2005) and, of cause, Sgr (Ibata et al. 2001;Majewski et al. 2003). This break corresponds to an excess of density that extends outside the King tidal radius. ...
We have studied the extent of the Red Giant Branch stellar population in the Fornax dwarf spheroidal galaxy using the spatially extended and homogeneous data set from Gaia EDR3. Our preselection of stars belonging to Fornax is based on their proper motions, parallaxes and color-magnitude diagram. The latter criteria provide a Fornax star sample, which we further restrict by color and magnitude to eliminate contaminations due to either Milky Way stars or QSOs. The precision of the data has been sufficient to reach extremely small contaminations (0.02 to 0.3%), allowing us to reach to a background level 12 magnitudes deeper than the central surface brightness of Fornax. We discover a break in the density profile, which reveals the presence of an additional component that extents 2.1 degree in radius, i.e. 5.4 kpc, and almost seven times the half-light radius of Fornax. The extended new component represents 10% of the stellar mass of Fornax, and behaves like an extended halo. The absence of tidally elongated features at such an unprecedented depth (equivalent to $37.94\pm0.16$ mag ${\rm arcsec}^{-2}$ in V-band) rules out a possible role of tidal stripping. We suggest instead that Fornax is likely at first infall, and has lost its gas very recently, which consequently leads to a lack of gravity implying that residual stars have spherically expanded to form the newly discovered stellar halo of Fornax.
... They exhibit high velocity dispersions (e.g. Simon & Geha 2007;Koch et al. 2009); in the range of 5 − 12 km s −1 and the velocity dispersion remains approximately constant with distance from the centre of the galaxy (Kleyna et al. 2002(Kleyna et al. , 2003Muñoz et al. 2005Muñoz et al. , 2006Simon & Geha 2007;Walker et al. 2007). ...
A variety of formation models for dwarf spheroidal (dSph) galaxies have been proposed in the literature, but these generally have not been quantitatively compared with observations. We make use of a new spectroscopic data-set for the Milky Way dSph Leo I, combining 288 stars observed with Magellan/IMACS and existing Keck/DEIMOS data to provide velocity and metallicity measurements for 953 Leo I member stars. We search for chemo-dynamical patterns in this data-set, mock galaxies consisting of pure random motions, and simulated dwarfs formed via the dissolving star cluster and tidal stirring models. In the Leo I data, we report the detection of 14 candidate streams of stars that may have originated in disrupted star clusters. The angular momentum vectors of these streams are randomly oriented, consistent with the lack of rotation in Leo I. These results are consistent with the predictions of the dissolving cluster model. In contrast, we find fewer candidate stream signals in mock data-sets that lack coherent motions ~99% of the time. The chemo-dynamical analysis of the tidal stirring simulation produces streams that share a common orientation, which is inconsistent with the Leo~I data.
... Both Majewski et al. ( 2008 ) and Carrera et al. ( 2011 ) find a decrease in the mean metallicity of RGB stars beyond a LMC galactocentric radius of ∼7 • , with mean [Fe/H] ∼−1 at distances of ≥10 • , with a scatter of ∼1 dex at these large distances. We also note that Munoz et al. ( 2006 ) measure a mean [Fe/H] = −0.67 and a dispersion of 0.62 dex -somewhat higher than our measurements -for a group of 15 stars in the vicinity of the Carina dwarf (located near the armlike feature at φ 1 ∼12.5 • ) with heliocentric velocities indicating a potential LMC association. Ho we ver, cross-matching these stars against Gaia EDR3 returns at least three stars with proper motions strongly inconsistent with being associated with the LMC, suggesting their reported mean metallicity could be too high (assuming the non-Magellanic stars are metal-rich Galactic contaminants). ...
... Ho we ver, cross-matching these stars against Gaia EDR3 returns at least three stars with proper motions strongly inconsistent with being associated with the LMC, suggesting their reported mean metallicity could be too high (assuming the non-Magellanic stars are metal-rich Galactic contaminants). Unfortunately, Munoz et al. ( 2006 ) do not report individual [Fe/H] measurements so we cannot calculate a corrected value. ...
The highly-substructured outskirts of the Magellanic Clouds provide ideal locations for studying the complex interaction history between both Clouds and the Milky Way (MW). In this paper, we investigate the origin of a >20○ long arm-like feature in the northern outskirts of the Large Magellanic Cloud (LMC) using data from the Magellanic Edges Survey (MagES) and Gaia EDR3. We find that the arm has a similar geometry and metallicity to the nearby outer LMC disk, indicating that it is comprised of perturbed disk material. Whilst the azimuthal velocity and velocity dispersions along the arm are consistent with those in the outer LMC, the in-plane radial velocity and out-of-plane vertical velocity are significantly perturbed from equilibrium disk kinematics. We compare these observations to a new suite of dynamical models of the Magellanic/MW system, which describe the LMC as a collection of tracer particles within a rigid potential, and the SMC as a rigid Hernquist potential. Our models indicate the tidal force of the MW during the LMC’s infall is likely responsible for the observed increasing out-of-plane velocity along the arm. Our models also suggest close LMC/SMC interactions within the past Gyr, particularly the SMC’s pericentric passage ∼150 Myr ago and a possible SMC crossing of the LMC disk plane ∼400 Myr ago, likely do not perturb stars that today comprise the arm. Historical interactions with the SMC prior to ∼1 Gyr ago may be required to explain some of the observed kinematic properties of the arm, in particular its strongly negative in-plane radial velocity.
... We find 1443 stars with RV data (Muñoz et al. 2006b;Walker et al. 2009;Fabrizio et al. 2016) in our full EDR3 catalog. From those 1190 have RV that are within 3 of the RV as obtained from S19. ...
We use Gaia EDR3 data to identify stars associated with six classical dwarf spheroidals (Draco, Ursa Minor, Sextans, Sculptor, Fornax, Carina) at their outermost radii, beyond their nominal King stellar limiting radius. For all of the dSphs examined, we find radial velocity matches with stars residing beyond the King limiting radius and with $> 50\%$ astrometric probability (four in Draco, two in Ursa Minor, eight in Sextans, two in Sculptor, twelve in Fornax, and five in Carina), indicating that these stars are associated with their respective dwarf spheroidals (dSphs) at high probability. We compare the positions of our candidate "extra-tidal" stars with the orbital tracks of the galaxies, and identify stars, both with and without radial velocity matches, that are consistent with lying along the orbital track of the satellites. Cross matching with publicly available catalogs of RR Lyrae, we find one RR Lyrae candidate with $> 50\%$ astrometric probability outside the limiting radius in each of Sculptor and Fornax, two such candidates in Draco, nine in Ursa Minor, seven in Sextans, and zero in Carina. Follow-up spectra on all of our candidates, including possible metallicity information, will help confirm association with their respective dSphs, and could represent evidence for extended stellar halos or tidal debris around these classical dSphs.
... Both Majewski et al. (2008) and Carrera et al. (2011) find a decrease in the mean metallicity of RGB stars beyond a LMC galactocentric radius of~7 • , with mean [Fe/H]~−1 at distances of ≥10 • , with a scatter of~1dex at these large distances. We also note that Munoz et al. (2006) measure a mean [Fe/H]= −0.67 and a dispersion of 0.62dex -somewhat higher than our measurements -for a group of 15 stars in the vicinity of the Carina dwarf (located near the armlike feature at 1~1 2.5 • ) with heliocentric velocities indicating a potential LMC association. However, cross-matching these stars against Gaia EDR3 returns at least three stars with proper motions strongly inconsistent with being associated with the LMC, suggesting their reported mean metallicity could be too high (assuming the non-Magellanic stars are metal-rich Galactic contaminants). ...
... However, cross-matching these stars against Gaia EDR3 returns at least three stars with proper motions strongly inconsistent with being associated with the LMC, suggesting their reported mean metallicity could be too high (assuming the non-Magellanic stars are metal-rich Galactic contaminants). Unfortunately, Munoz et al. (2006) outer LMC disk fields (Paper I), and given the negative metallicity gradient at smaller LMC radii (Carrera et al. 2011;Majewski et al. 2008), a mild negative metallicity gradient could be expected under the assumption that the feature is an overdensity in the extreme LMC disk outskirts, such that stars currently located at large distances along the feature had their origin at larger radii than stars currently located at smaller galactocentric radii. We explore formation mechanisms for the feature using models to test this idea in §4. ...
The highly-substructured outskirts of the Magellanic Clouds provide ideal locations for studying the complex interaction history between both Clouds and the Milky Way (MW). In this paper, we investigate the origin of a >20$^\circ$ long arm-like feature in the northern outskirts of the Large Magellanic Cloud (LMC) using data from the Magellanic Edges Survey (MagES) and Gaia EDR3. We study the metallicity, structure, and kinematics of the arm, finding it has a similar geometry and [Fe/H] abundance to the nearby outer LMC disk, and is likely comprised of perturbed disk material. Whilst the azimuthal velocity and velocity dispersions along the arm are consistent with those in the outer LMC, the in-plane radial velocity and out-of-plane vertical velocity are significantly perturbed from equilibrium disk kinematics. Comparison with a new suite of dynamical models of the Magellanic/MW system reveals the tidal force of the MW during the LMC's infall is primarily responsible for the formation of the arm. Close LMC/SMC interactions within the past Gyr, particularly the SMC's pericentric passage ~150 Myr ago and a recent SMC crossing of the LMC disk plane ~400 Myr ago, do not perturb stars that today comprise the arm, and are instead likely responsible for structures in the western LMC disk. Nonetheless, historical interactions with the SMC prior to ~1 Gyr ago may be required to explain some of the observed kinematic properties of the arm, in particular a strongly negative in-plane radial velocity.
... Our Local Group constitutes an excellent workplace to perform Galactic Archaeology because many clues about galaxy assembly and evolution processes persist -often as coherent substructures -in the faint outskirts of galaxies (Bekki & Chiba 2005;Muñoz et al. 2006;Read, Pontzen & Viel 2006;Harmsen et al. 2017;Kallivayalil et al. 2018;Mackey et al. 2018;Belokurov & Erkal 2019). Hence, studying the dynamically unrelaxed edges of nearby galaxies is particularly effective. ...
The periphery of the Small Magellanic Cloud (SMC) can unlock important information regarding galaxy formation and evolution in interacting systems. Here, we present a detailed study of the extended stellar structure of the SMC using deep colour–magnitude diagrams, obtained as part of the Survey of the MAgellanic Stellar History (SMASH). Special care was taken in the decontamination of our data from Milky Way (MW) foreground stars, including from foreground globular clusters NGC 362 and 47 Tuc. We derived the SMC surface brightness using a ‘conservative’ approach from which we calculated the general parameters of the SMC, finding a staggered surface brightness profile. We also traced the fainter outskirts by constructing a stellar density profile. This approach, based on stellar counts of the oldest main-sequence turn-off stars, uncovered a tidally disrupted stellar feature that reaches as far out as 12 deg from the SMC centre. We also serendipitously found a faint feature of unknown origin located at ∼14 deg from the centre of the SMC and that we tentatively associated with a more distant structure. We compared our results to in-house simulations of a 1 × 109 M⊙ SMC, finding that its elliptical shape can be explained by its tidal disruption under the combined presence of the MW and the Large Magellanic Cloud. Finally, we found that the older stellar populations show a smooth profile while the younger component presents a jump in the density followed by a flat profile, confirming the heavily disturbed nature of the SMC.
