ﻻ يوجد ملخص باللغة العربية
Using the VLA and ALMA, we have obtained CO(2-1), [C II], [N II] line emission and multiple dust continuum measurements in a sample of normal galaxies at $z=5-6$. We report the highest redshift detection of low-$J$ CO emission from a Lyman Break Galaxy, at $zsim5.7$. The CO line luminosity implies a massive molecular gas reservoir of $(1.3pm0.3)(alpha_{rm CO}/4.5,M_odot$ (K km s$^{-1}$ pc$^2)^{-1})times10^{11},M_odot$, suggesting low star formation efficiency, with a gas depletion timescale of order $sim$1 Gyr. This efficiency is much lower than traditionally observed in $zgtrsim5$ starbursts, indicating that star forming conditions in Main Sequence galaxies at $zsim6$ may be comparable to those of normal galaxies probed up to $zsim3$ to-date, but with rising gas fractions across the entire redshift range. We also obtain a deep CO upper limit for a Main Sequence galaxy at $zsim5.3$ with $sim3$ times lower SFR, perhaps implying a high $alpha_{rm CO}$ conversion factor, as typically found in low metallicity galaxies. For a sample including both CO targets, we also find faint [N II] 205$,mu$m emission relative to [C II] in all but the most IR-luminous normal galaxies at $z=5-6$, implying more intense or harder radiation fields in the ionized gas relative to lower redshift. These radiation properties suggest that low metallicity may be common in typical $sim$10$^{10},M_odot$ galaxies at $z=5-6$. While a fraction of Main Sequence star formation in the first billion years may take place in conditions not dissimilar to lower redshift, lower metallicity may affect the remainder of the population.
We report interferometric measurements of [NII] 205 um fine-structure line emission from a representative sample of three galaxies at z=5-6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [CII] and far
We investigate the star formation histories (SFHs) of high redshift (3 <~ z <~ 5) star-forming galaxies selected based on their rest-frame ultraviolet (UV) colors in the CANDELS/GOODS-S field. By comparing the results from the spectral-energy-distrib
Aims. We present a spectroscopic study of the properties of 64 Balmer break galaxies that show signs of star formation. The studied sample of star-forming galaxies spans a redshift range from 0.094 to 1.475 with stellar masses in the range 10$^{8}-$1
We explore how the star formation efficiency in a protocluster clump is regulated by metallicity dependent stellar winds from the newly formed massive OB stars (Mstar >5 Msol). The model describes the co-evolution of the mass function of gravitationa
We investigate the relation between star formation rates ($dot{M}_{s}$) and AGN properties in optically selected type 1 quasars at $2<z<3$ using data from Herschel and the SDSS. We find that $dot{rm{M}}_s$ remains approximately constant with redshift