3 research outputs found
JCMT/SCUBA-2 uncovers an excess of m counts on megaparsec scales around high-redshift quasars. Characterization of the overdensities and their alignment with the quasars' Ly nebulae
We conducted a systematic survey of the environment of high-z quasars at
submillimeter wavelengths to unveil and characterize the surrounding
distribution of dusty submillimeter galaxies (SMGs). We took sensitive
JCMT/SCUBA-2 observations for 3 enormous Lyman-alpha nebulae (ELANe) and 17
quasar fields in the redshift range 2<z<4.2 selected from recent Ly
surveys. These observations uncovered 523 and 101 sources at 850m and
450m, respectively, with S/N>4 or detected in both bands at S/N>3. We ran
Monte Carlo simulations to construct 850m number counts and unveil an
excess of sources in 75% of the targeted fields. Overall, regions around ELANe
and quasars are overabundant with respect to blank fields by a factor of
and , respectively. Therefore, the excess of SMGs is
likely part of the Mpc-scale environment around these systems. By combining all
fields and repeating the count analysis in radial apertures, we find a decrease
in the overdensity factor from >3 within cMpc to at the edge
of the surveyed field ( cMpc), suggesting that the physical extent of
the overdensities is larger than our maps. We computed preferred directions for
the overdensities of SMGs from the positions of the sources and used them to
orient and create stacked maps of source densities for the quasars'
environment. This stacking unveils an elongated structure reminiscent of a
large-scale filament with a scale width of cMpc. Finally, the
directions of the overdensities are roughly aligned with the major axis of the
Ly nebulae, suggesting that the latter trace, on hundreds of kpc, the
central regions of the projected large-scale structure described by the SMGs on
Mpc scales. Confirming member associations of the SMGs is required to further
characterize their spatial and kinematic distribution around ELANe and quasars.Comment: 37 pages, 12 figures, 8 appendix; A&A in pres
A MUltiwavelength Study of ELAN Environments (AMUSE
We have been undertaking a systematic survey at 850 μm based on a sample of four prototypical z ∼ 2 − 3 enormous Lyα nebulae (ELANe) as well as their megaparsec-scale (Mpc-scale) environments to study the physical connections between ELANe and their coeval dusty submillimeter galaxies (SMGs). By analysing the SCUBA-2 data with self-consistent Monte Carlo simulations to construct the number counts, here, we report on the overabundance of 850 μm-selected submillimeter sources around all the four ELANe, by a factor of 3.6 ± 0.6 (weighted average) compared to the blank fields. This suggests that the excessive number of submillimeter sources are likely to be part of the Mpc-scale environment around the ELANe, corroborating the co-evolution scenario for SMGs and quasars; this is a process which may be more commonly observed in the ELAN fields. If the current form of the underlying count models continues toward the fainter end, our results would suggest an excess of the 850 μm extragalactic background light by a factor of between 2–10, an indication of significant background light fluctuations on the survey scales. Finally, by assuming that all the excessive submillimeter sources are associated with their corresponding ELAN environments, we estimate the SFR densities of each ELAN field, as well as a weighted average of ΣSFR = 1200 ± 300 M⊙ yr−1 Mpc−3, consistent with that found in the vicinity of other quasar systems or proto-clusters at similar redshifts; in addition, it is a factor of about 300 greater than the cosmic mean
Target Selection and Sample Characterization for the DESI LOW-Z Secondary Target Program
We introduce the DESI LOW-Z Secondary Target Survey, which combines the wide area capabilities of the Dark Energy Spectroscopic Instrument (DESI) with an efficient, low-redshift target selection method. Our selection consists of a set of color and surface brightness cuts, combined with modern machine learning methods, to optimally target low-redshift dwarf galaxies (z 95% complete in target selection at z < 0.03 between 19 <r < 21. The full five-year DESI program will expand the LOW-Z sample, densely mapping the low-redshift Universe and providing critical information about how to pursue effective and efficient low-redshift surveys