ABSTRACT Recently a population of large, very low surface brightness, spheroidal galaxies was identified in the Coma cluster. The apparent survival of these ultra-diffuse galaxies (UDGs) in a rich ...cluster suggests that they have very high masses. Here, we present the stellar kinematics of Dragonfly 44, one of the largest Coma UDGs, using a 33.5 hr integration with DEIMOS on the Keck II telescope. We find a velocity dispersion of = 47 − 6 + 8 km s − 1 , which implies a dynamical mass of M dyn ( < r 1 / 2 ) = 0.7 − 0.2 + 0.3 × 10 10 M within its deprojected half-light radius of r 1 / 2 = 4.6 0.2 kpc . The mass-to-light ratio is M / L I ( < r 1 / 2 ) = 48 − 14 + 21 M / L , and the dark matter fraction is 98% within r 1 / 2 . The high mass of Dragonfly 44 is accompanied by a large globular cluster population. From deep Gemini imaging taken in 0 4 seeing we infer that Dragonfly 44 has 94 − 20 + 25 globular clusters, similar to the counts for other galaxies in this mass range. Our results add to other recent evidence that many UDGs are "failed" galaxies, with the sizes, dark matter content, and globular cluster systems of much more luminous objects. We estimate the total dark halo mass of Dragonfly 44 by comparing the amount of dark matter within r = 4.6 kpc to enclosed mass profiles of NFW halos. The enclosed mass suggests a total mass of ∼ 10 12 M , similar to the mass of the Milky Way. The existence of nearly dark objects with this mass is unexpected, as galaxy formation is thought to be maximally efficient in this regime.
We present COSMOS-Drift And SHift (DASH), a Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging survey of the COSMOS field in the H160 filter. The survey comprises 456 individual WFC3 ...pointings corresponding to an area of 0.49 deg2 (0.66 deg2 when including archival data) and reaches a 5 point-source limit of H160 = 25.1 (0 3 aperture). COSMOS-DASH is the widest HST/WFC3 imaging survey in the H160 filter, tripling the extragalactic survey area in the near-infrared at HST resolution. We make the reduced H160 mosaic available to the community. We use this data set to measure the sizes of 169 galaxies with at 1.5 < z < 3.0 and augment this sample with 749 galaxies at 0.1 < z < 1.5 using archival ACS imaging. We find that the median size of galaxies in this mass range changes with redshift as kpc. Separating the galaxies into star-forming and quiescent galaxies using their rest-frame U − V and V − J colors, we find no statistical difference between the median sizes of the most massive star-forming and quiescent galaxies at : they are 4.9 0.9 kpc and 4.3 0.3 kpc, respectively. However, we do find a significant difference in the Sèrsic index between the two samples, such that massive quiescent galaxies have higher central densities than star-forming galaxies. We extend the size−mass analysis to lower masses by combining it with the 3D-HST/CANDELS sample of van der Wel et al. and derive empirical relations between size, mass, and redshift. Fitting a relation of the form , with and reff in kpc, we find log A = −0.25 log(1 + z) + 0.80 and = −0.13 log(1 + z) + 0.27. We also provide relations for the subsamples of star-forming and quiescent galaxies. Our results confirm previous studies that were based on smaller samples or ground-based imaging.
Abstract
Recent studies have indicated that the ratio between half-mass and half-light radii,
r
mass
/
r
light
, varies significantly as a function of stellar mass and redshift, complicating the ...interpretation of the ubiquitous
r
light
−
M
*
relation. To investigate, in this study we construct the light and color profiles of ∼3000 galaxies at 1 <
z
< 2 with
log
M
*
/
M
⊙
>
10.25
using
imcascade
, a Bayesian implementation of the Multi-Gaussian Expansion (MGE) technique.
imcascade
flexibly represents galaxy profiles using a series of Gaussians, free of any a priori parameterization. We find that both star-forming and quiescent galaxies have, on average, negative color gradients. For star-forming galaxies, we find steeper gradients that evolve with redshift and correlate with dust content. Using the color gradients as a proxy for gradients in the
M
/
L
ratio, we measure half-mass radii for our sample of galaxies. There is significant scatter in individual
r
mass
/
r
light
ratios, which is correlated with variation in the color gradients. We find that the median
r
mass
/
r
light
ratio evolves from 0.75 at
z
= 2 to 0.5 at
z
= 1, consistent with previous results. We characterize the
r
mass
−
M
*
relation, and we find that it has a shallower slope and shows less redshift evolution than the
r
light
−
M
*
relation. This applies both to star-forming and quiescent galaxies. We discuss some of the implications of using
r
mass
instead of
r
light
, including an investigation of the size−inclination bias and a comparison to numerical simulations.
We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging of 23 very low surface brightness ( e,V ∼ 25-27.5) galaxies detected in the fields of four nearby galaxy groups. These ...objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array. Seven are newly identified, while most of the others had been seen previously in visual surveys of deep photographic plates and more recent surveys. Few have previously been studied in detail. From the ACS images, we measure distances to the galaxies using both the tip of the red giant branch method and the surface brightness fluctuations method. We demonstrate that the two methods are consistent with each other in the regime where both can be applied. The distances to 15 out of 20 galaxies with stable measurements are consistent with that of the targeted group within errors. This suggests that assuming group membership based solely on projected proximity is ∼75% successful in this regime. The galaxies are nearly round, with a median axis ratio of 0.85, and visually resemble dwarf spheroidal galaxies. The objects have a range of sizes, from Re = 0.4 kpc to Re = 1.8 kpc, with a median . They range in luminosity from MV = −11.4 to MV = −15.6, with a median . Galaxies with Re ∼ 1 kpc and MV ∼ −12 are fairly rare in the Local Group, but we find many of them in this relatively small sample. Four of the objects fall in the class of ultra-diffuse galaxies, with Re > 1.5 kpc and 0,V > 24 mag arcsec−2, including the recently identified dark matter deficient galaxy NGC 1052-DF2.
ABSTRACT
We present a new parametric lens model for the massive galaxy cluster Abell 2744 based on new ultra-deep JWST imaging taken in the framework of the UNCOVER program. These observations ...constitute the deepest JWST images of a lensing cluster to date, adding to existing deep Hubble Space Telescope (HST) images and the recent JWST Early Release Science and Director’s Discretionary Time data taken for this field. The wide field of view of UNCOVER (∼45 arcmin2) extends beyond the cluster’s well-studied central core and reveals a spectacular wealth of prominent lensed features around two massive cluster sub-structures in the north and north-west, where no multiple images were previously known. We identify 75 new multiple images and candidates of 17 sources, 43 of which allow us, for the first time, to constrain the lensing properties and total mass distribution around these extended cluster structures using strong lensing (SL). Our model yields an effective Einstein radius of θE, main = 23.2 ± 2.3 arcsec for the main cluster core (for zs = 2), enclosing a mass of M(< θE, main) = (7.7 ± 1.1) × 1013 M⊙, and θE, NW = 13.1 ± 1.3 arcsec for the newly discovered north-western SL structure enclosing M(< θE, NW) = (2.2 ± 0.3) × 1013 M⊙. The northern clump is somewhat less massive with θE, N = 7.4 ± 0.7 arcsec enclosing M(< θE, N) = (0.8 ± 0.1) × 1013 M⊙. We find the northern sub-structures of Abell 2744 to broadly agree with the findings from weak lensing analyses and align with the filamentary structure found by these previous studies. Our model in particular reveals a large area of high magnification values between the various cluster structures, which will be paramount for lensed galaxy studies in the UNCOVER field. The model is made publicly available to accompany the first UNCOVER data release.
ABSTRACT
We compare the star-forming main sequence (SFMS) of galaxies – both integrated and resolved on 1 kpc scales – between the high-resolution TNG50 simulation of IllustrisTNG and observations ...from the 3D-HST slitless spectroscopic survey at z ∼ 1. Contrasting integrated star formation rates (SFRs), we find that the slope and normalization of the star-forming main sequence in TNG50 are quantitatively consistent with values derived by fitting observations from 3D-HST with the Prospector Bayesian inference framework. The previous offsets of 0.2–1 dex between observed and simulated main-sequence normalizations are resolved when using the updated masses and SFRs from Prospector. The scatter is generically smaller in TNG50 than in 3D-HST for more massive galaxies with M*> 1010 M⊙, by ∼10–40 per cent, after accounting for observational uncertainties. When comparing resolved star formation, we also find good agreement between TNG50 and 3D-HST: average specific star formation rate (sSFR) radial profiles of galaxies at all masses and radii below, on, and above the SFMS are similar in both normalization and shape. Most noteworthy, massive galaxies with M*> 1010.5 M⊙, which have fallen below the SFMS due to ongoing quenching, exhibit a clear central SFR suppression, in both TNG50 and 3D-HST. In contrast, the original Illustris simulation and a variant TNG run without black hole kinetic wind feedback, do not reproduce the central SFR profile suppression seen in data. In TNG, inside-out quenching is due to the supermassive black hole (SMBH) feedback model operating at low accretion rates.
We present a description of the Dragonfly Wide Field Survey (DWFS), a deep photometric survey of a wide area of sky. The DWFS covers 330 deg2 in the equatorial GAMA fields and the Stripe 82 fields in ...the SDSS g and r bands. It is carried out with the 48-lens Dragonfly Telephoto Array, a telescope that is optimized for the detection of low surface brightness emission. The main goal of the survey is to study the dwarf galaxy population beyond the Local Group. In this paper, we describe the survey design and show early results. We reach 1 depths of g 31 mag arcsec−2 on arcminute scales and show that Milky Way satellites such as Sextans, Bootes, and Ursa Major should be detectable out to D 10 Mpc. We also provide an overview of the elements and operation of the 48-lens Dragonfly telescope and a detailed description of its data reduction pipeline. The pipeline is fully automated, with individual frames subjected to a rigorous series of quality tests. The sky subtraction is performed in two stages, ensuring that emission features with spatial scales up to ∼0 9 × 0 6 are preserved. The DWFS provides unparalleled sensitivity to low surface brightness features on arcminute scales.
We recently found an ultra diffuse galaxy (UDG) with a half-light radius of Re = 2.2 kpc and little or no dark matter. The total mass of NGC1052-DF2 was measured from the radial velocities of bright ...compact objects that are associated with the galaxy. Here, we analyze these objects using a combination of Hubble Space Telescope (HST) imaging and Keck spectroscopy. Their average size is pc and their average ellipticity is . From a stacked Keck spectrum we derive an age of 9 Gyr and a metallicity of Fe/H = −1.35 0.12. Their properties are similar to Centauri, the brightest and largest globular cluster in the Milky Way, and our results demonstrate that the luminosity function of metal-poor globular clusters is not universal. The fraction of the total stellar mass that is in the globular cluster system is similar to that in other UDGs, and consistent with "failed galaxy" scenarios, where star formation terminated shortly after the clusters were formed. However, the galaxy is a factor of ∼1000 removed from the relation between globular cluster mass and total galaxy mass that has been found for other galaxies, including other UDGs. We infer that a dark matter halo is not a prerequisite for the formation of metal-poor globular cluster-like objects in high-redshift galaxies.
Structural Evolution in Massive Galaxies at z ∼ 2 Tadaki, Ken-ichi; Belli, Sirio; Burkert, Andreas ...
Astrophysical journal/The Astrophysical journal,
09/2020, Volume:
901, Issue:
1
Journal Article
Peer reviewed
Open access
We present 0 2 resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations at 870 m in a stellar mass-selected sample of 85 massive ( ) star-forming galaxies (SFGs) at in the ...CANDELS/3D-Hubble Space Telescope fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from to . The effective radius of the FIR emission is smaller by a factor of than the effective radius of the optical emission and is smaller by a factor of than the half-mass radius. Taking into account potential extended components, the FIR size would change only by ∼10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1 kpc, . The compact starburst puts most of the massive SFGs on the mass-size relation for quiescent galaxies (QGs) at z ∼ 2 within 300 Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300 Myr, ∼38% of massive SFGs can reach the central mass of , which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870 m and James Webb Space Telescope 3-4 m will explicitly verify this scenario.
Abstract We present the elemental abundances and ages of 19 massive quiescent galaxies at z ∼ 1.4 and z ∼ 2.1 from the Keck Heavy Metal Survey. The ultradeep LRIS and MOSFIRE spectra were modeled ...using a full-spectrum stellar population fitting code with variable abundance patterns. The galaxies have iron abundances between Fe/H = −0.5 and −0.1 dex, with typical values of −0.2 −0.3 at z ∼ 1.4 z ∼ 2.1. We also find a tentative log σ v –Fe/H relation at z ∼ 1.4. The magnesium-to-iron ratios span Mg/Fe = 0.1–0.6 dex, with typical values of 0.3 0.5 dex at z ∼ 1.4 z ∼ 2.1. The ages imply formation redshifts of z form = 2–8. Compared to quiescent galaxies at lower redshifts, we find that Fe/H was ∼0.2 dex lower at z = 1.4–2.1. We find no evolution in Mg/Fe out to z ∼ 1.4, though the z ∼ 2.1 galaxies are 0.2 dex enhanced compared to z = 0–0.7. A comparison of these results to a chemical evolution model indicates that galaxies at higher redshift form at progressively earlier epochs and over shorter star formation timescales, with the z ∼ 2.1 galaxies forming the bulk of their stars over 150 Myr at z form ∼ 4. This evolution cannot be solely attributed to an increased number of quiescent galaxies at later times; several Heavy Metal galaxies have extreme chemical properties not found in massive galaxies at z ∼ 0.0–0.7. Thus, the chemical properties of individual galaxies must evolve over time. Minor mergers also cannot fully account for this evolution as they cannot increase Fe/H, particularly in galaxy centers. Consequently, the buildup of massive quiescent galaxies since z ∼ 2.1 may require further mechanisms, such as major mergers and/or central star formation.
PDF
