We study the stellar mass functions (SMFs) of star-forming and quiescent galaxies in 11 galaxy clusters at 1.0 <
z
< 1.4 drawn from the Gemini Observations of Galaxies in Rich Early ENvironments ...(GOGREEN) survey. Based on more than 500 h of Gemini/GMOS spectroscopy and deep multi-band photometry taken with a range of observatories, we probe the SMFs down to a stellar mass limit of 10
9.7
M
⊙
(10
9.5
M
⊙
for star-forming galaxies). At this early epoch, the fraction of quiescent galaxies is already highly elevated in the clusters compared to the field at the same redshift. The quenched fraction excess (QFE) represents the fraction of galaxies that would be star-forming in the field but are quenched due to their environment. The QFE is strongly mass dependent, and increases from ∼30% at
M
⋆
= 10
9.7
M
⊙
to ∼80% at
M
⋆
= 10
11.0
M
⊙
. Nonetheless, the shapes of the SMFs of the two individual galaxy types, star-forming and quiescent galaxies, are identical between cluster and field to high statistical precision. Nevertheless, along with the different quiescent fractions, the total galaxy SMF is also environmentally dependent, with a relative deficit of low-mass galaxies in the clusters. These results are in stark contrast with findings in the local Universe, and therefore require a substantially different quenching mode to operate at early times. We discuss these results in light of several popular quenching models.
Abstract
We present near-infrared spectroscopic confirmations of a sample of 16 photometrically selected galaxies with stellar masses
>11 at redshift
z
> 3 from the XMM-VIDEO and COSMOS-UltraVISTA ...fields using Keck/MOSFIRE as part of the Massive Ancient Galaxies At
z
> 3 NEar-infrared (MAGAZ3NE) survey. Eight of the ultramassive galaxies (UMGs) have specific star formation rates (sSFR) < 0.03 Gyr
−1
, with negligible emission lines. Another seven UMGs show emission lines consistent with active galactic nuclei and/or star formation, while only one UMG has sSFR > 1 Gyr
−1
. Model star formation histories of these galaxies describe systems that formed the majority of their stars in vigorous bursts of several hundred megayear duration around
during which hundreds to thousands of solar masses were formed per year. These formation ages of <1 Gyr prior to observation are consistent with ages derived from measurements of
D
n
(4000) and
(H
δ
). Rapid quenching followed these bursty star-forming periods, generally occurring less than 350 Myr before observation, resulting in post-starburst SEDs and spectra for half the sample. The rapid formation timescales are consistent with the extreme star formation rates observed in
dusty starbursts observed with ALMA, suggesting that such dusty galaxies are progenitors of these UMGs. While such formation histories have been suggested in previous studies, the large sample introduced here presents the most compelling evidence yet that vigorous star formation followed by rapid quenching is almost certainly the norm for high-mass galaxies in the early universe. The UMGs presented here were selected to be brighter than
K
s
= 21.7, raising the intriguing possibility that even (fainter) older quiescent UMGs could exist at this epoch.
Abstract
We report the discovery of MAGAZ3NE J095924+022537, a spectroscopically confirmed protocluster at
z
=
3.3665
−
0.0012
+
0.0009
around a spectroscopically confirmed
UVJ
-quiescent ...ultramassive galaxy (UMG;
M
⋆
=
2.34
−
0.34
+
0.23
×
10
11
M
⊙
) in the COSMOS UltraVISTA field. We present a total of 38 protocluster members (14 spectroscopic and 24 photometric), including the UMG. Notably, and in marked contrast to protoclusters previously reported at this epoch that have been found to contain predominantly star-forming members, we measure an elevated fraction of quiescent galaxies relative to the coeval field (
73.3
−
16.9
+
26.7
%
versus
11.6
−
4.9
+
7.1
%
for galaxies with stellar mass
M
⋆
≥ 10
11
M
⊙
). This high quenched fraction provides a striking and important counterexample to the seeming ubiquitousness of star-forming galaxies in protoclusters at
z
> 2 and suggests, rather, that protoclusters exist in a diversity of evolutionary states in the early universe. We discuss the possibility that we might be observing either “early mass quenching” or nonclassical “environmental quenching.” We also present the discovery of MAGAZ3NE J100028+023349, a second spectroscopically confirmed protocluster, at a very similar redshift of
z
=
3.3801
−
0.0281
+
0.0213
. We present a total of 20 protocluster members, 12 of which are photometric and eight spectroscopic including a poststarburst UMG (
M
⋆
=
2.95
−
0.20
+
0.21
×
10
11
M
⊙
). Protoclusters MAGAZ3NE J0959 and MAGAZ3NE J1000 are separated by 18′ on the sky (35 comoving Mpc), in good agreement with predictions from simulations for the size of “Coma”-type cluster progenitors at this epoch. It is highly likely that the two UMGs are the progenitors of Brightest Cluster Galaxies seen in massive virialized clusters at lower redshift.
ABSTRACT
We use photometric redshifts and statistical background subtraction to measure stellar mass functions in galaxy group-mass (4.5−8 × 1013 M⊙) haloes at 1 < z < 1.5. Groups are selected from ...COSMOS and SXDF, based on X-ray imaging and sparse spectroscopy. Stellar mass (Mstellar) functions are computed for quiescent and star-forming galaxies separately, based on their rest-frame UVJ colours. From these we compute the quiescent fraction and quiescent fraction excess (QFE) relative to the field as a function of Mstellar. QFE increases with Mstellar, similar to more massive clusters at 1 < z < 1.5. This contrasts with the apparent separability of Mstellar and environmental factors on galaxy quiescent fractions at z ∼ 0. We then compare our results with higher mass clusters at 1 < z < 1.5 and lower redshifts. We find a strong QFE dependence on halo mass at fixed Mstellar; well fit by a logarithmic slope of d(QFE)/dlog (Mhalo) ∼ 0.24 ± 0.04 for all Mstellar and redshift bins. This dependence is in remarkably good qualitative agreement with the hydrodynamic simulation bahamas, but contradicts the observed dependence of QFE on Mstellar. We interpret the results using two toy models: one where a time delay until rapid (instantaneous) quenching begins upon accretion to the main progenitor (‘no pre-processing’) and one where it starts upon first becoming a satellite (‘pre-processing’). Delay times appear to be halo mass-dependent, with a significantly stronger dependence required without pre-processing. We conclude that our results support models in which environmental quenching begins in low-mass (<1014M⊙) haloes at z > 1.
ABSTRACT
We measure the rate of environmentally driven star formation quenching in galaxies at z ∼ 1, using eleven massive ($M\approx 2\times 10^{14}\, \mathrm{M}_\odot$) galaxy clusters spanning a ...redshift range 1.0 < z < 1.4 from the GOGREEN sample. We identify three different types of transition galaxies: ‘green valley’ (GV) galaxies identified from their rest-frame (NUV − V) and (V − J) colours; ‘blue quiescent’ (BQ) galaxies, found at the blue end of the quiescent sequence in (U − V) and (V − J) colour; and spectroscopic post-starburst (PSB) galaxies. We measure the abundance of these galaxies as a function of stellar mass and environment. For high-stellar mass galaxies (log M/M⊙ > 10.5) we do not find any significant excess of transition galaxies in clusters, relative to a comparison field sample at the same redshift. It is likely that such galaxies were quenched prior to their accretion in the cluster, in group, filament, or protocluster environments. For lower stellar mass galaxies (9.5 < log M/M⊙ < 10.5) there is a small but significant excess of transition galaxies in clusters, accounting for an additional ∼5–10 per cent of the population compared with the field. We show that our data are consistent with a scenario in which 20–30 per cent of low-mass, star-forming galaxies in clusters are environmentally quenched every Gyr, and that this rate slowly declines from z = 1 to z = 0. While environmental quenching of these galaxies may include a long delay time during which star formation declines slowly, in most cases this must end with a rapid (τ < 1 Gyr) decline in star formation rate.
Ethics is integral to design in many ways. But design ethics has remained under-developed despite an increasing relevance in the Anthropocene, when many novel ethical issues and problems are ...anticipated to emerge from man-made artifacts and systems. The aim of this article is to revitalize the discourse of design ethics. Firstly, I define ‘design ethics’ in relation to the distinction between ‘ethics’ and ‘morality’. Secondly and through the perspective of ethics, I draw out new issues and questions by examining three commonly encountered categories in design, namely, ‘technology’, ‘sustainability’ and ‘responsibility’. Finally, I conclude by suggesting that it is important not to relinquish the formative potential of ethics for design despite its complexity, or its ostensible intractability.
•Ethics is integral to the activity of design in many ways.•Design ethics is however an under-developed area of research.•In the Anthropocene, many ethical issues are anticipated to emerge from man-made systems.•The categories of ‘technology’, ‘sustainability’ and ‘responsibility’ are examined.
Abstract
We present the census of massive (log(
M
*
/
M
⊙
) > 11) galaxies at 3 <
z
< 6 identified over the COSMOS/UltraVISTA Ultra-Deep field stripes: consisting of ≈100 and ≈20 high-confidence ...candidates at 3 <
z
< 4 and 4 <
z
< 6, respectively. The 3 <
z
< 4 population is comprised of post-starburst, UV-star-forming, and dusty star-forming galaxies in roughly equal fractions, while UV-star-forming galaxies dominate at 4 <
z
< 6 . We account for various sources of biases in the spectral energy distribution (SED) modeling, finding that the treatment of emission line contamination is essential for understanding the number densities and mass growth histories of massive galaxies at
z
> 3. The significant increase in observed number densities at
z
∼ 4 (> × 5 in ≲600 Myr) implies that this is the epoch at which log(
M
*
/
M
⊙
) > 11 galaxies emerge in significant numbers, with stellar ages (≈500–900 Myr) indicating rapid formation epochs as early as
z
∼ 7. Leveraging ancillary multiwavelength data sets, we perform panchromatic SED modeling to constrain the total star formation activity of the sample. The star formation activity of the sample is generally consistent with being on the star formation main sequence at the considered redshifts, with ≈15%–25% of the population showing evidence of suppressed star formation rates, indicating that quenching mechanisms are already at play by
z
∼ 4. We stack the available Hubble Space Telescope imaging, confirming their compact nature (
r
e
≲ 2.2 kpc), consistent with expected sizes of high-
z
star-forming galaxies. Finally, we discuss how our results are in-line with the early formation epochs and short formation timescales inferred from the fossil records of the most massive galaxies in the universe.
ABSTRACT
We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1 < z < 1.5 from the Gemini Observations ...of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determine the SFHs of individual galaxies by simultaneously fitting rest-frame optical spectroscopy and broad-band photometry to stellar population models. We confirm that the SFHs are consistent with more massive galaxies having on average earlier formation times. Comparing galaxies found in massive clusters with those in the field, we find galaxies with M* < 1011.3 M⊙ in the field have more extended SFHs. From the SFHs we calculate the mass-weighted ages, and compare age distributions of galaxies between the two environments, at fixed mass. We constrain the difference in mass-weighted ages between field and cluster galaxies to $0.31_{^{-0.33}}^{_{+0.51}}$ Gyr, in the sense that cluster galaxies are older. We place this result in the context of two simple quenching models and show that neither environmental quenching based on time since infall (without pre-processing) nor a difference in formation times alone can reproduce both the average age difference and relative quenched fractions. This is distinctly different from local clusters, for which the majority of the quenched population is consistent with having been environmentally quenched upon infall. Our results suggest that quenched population in galaxy clusters at z > 1 has been driven by different physical processes than those at play at z = 0.
Tour recommendation and itinerary planning are challenging tasks for tourists, due to their need to select points of interest (POI) to visit in unfamiliar cities and to select POIs that align with ...their interest preferences and trip constraints. We propose an algorithm called
PersTour
for recommending personalized tours using POI popularity and user interest preferences, which are automatically derived from real-life travel sequences based on geo-tagged photographs. Our tour recommendation problem is modeled using a formulation of the Orienteering problem and considers user trip constraints such as time limits and the need to start and end at specific POIs. In our work, we also reflect levels of user interest based on visit durations and demonstrate how POI visit duration can be personalized using this time-based user interest. Furthermore, we demonstrate how
PersTour
can be further enhanced by: (i) a weighted updating of user interests based on the recency of their POI visits and (ii) an automatic weighting between POI popularity and user interests based on the tourist’s activity level. Using a Flickr dataset of ten cities, our experiments show the effectiveness of
PersTour
against various collaborative filtering and greedy-based baselines, in terms of tour popularity, interest, recall, precision and F
1
-score. In particular, our results show the merits of using time-based user interest and personalized POI visit durations, compared to the current practice of using frequency-based user interest and average visit durations.
Abstract
We present new Atacama Large Millimeter/submillimeter Array (ALMA) results obtained from spatially resolved CO
J
= 2–1 line (0.″4 resolution) and 870
μ
m continuum (0.″2 resolution) ...observations of cluster galaxies in XMMXCS J2215.9-1738 at
z
= 1.46. Our sample comprises 17 galaxies within ∼0.5 Mpc (0.6
R
200
) of the cluster center, all of which have previously been detected in the CO
J
= 2–1 line at a lower resolution. The effective radii of both the CO
J
= 2–1 line and 870
μ
m dust continuum emissions are robustly measured for nine galaxies by modeling the visibilities. We find that the CO
J
= 2–1 line emission in all of the nine galaxies is more extended than the dust continuum emission by a factor of 2.8 ± 1.4. We investigate the spatially resolved Kennicutt–Schmidt (KS) relation in two regions within the interstellar medium of the galaxies. The relation for our sample reveals that the central region (0 <
r
<
R
e
,870
μ
m
) of galaxies tends to have a shorter gas depletion timescale, i.e., a higher star formation efficiency, compared to the extended region (
R
e
,870
μ
m
<
r
<
R
e
,CO
). Overall, our result suggests that star formation activities are concentrated inside the extended gas reservoir, possibly resulting in the formation of a bulge structure. We find consistency between the ALMA 870
μ
m radii of star-forming members and the Hubble Space Telescope/1.6
μ
m radii of passive members in a mass–size distribution, which suggests a transition from star-forming to passive members within ∼0.5 Gyr. In addition, no clear differences in the KS relation nor in the sizes are found between galaxies with and without a close companion.
PDF
