%0 Generic %1 jin2019discovery %A Jin, S. %A Daddi, E. %A Magdis, G. E. %A Liu, D. %A Schinnerer, E. %A Papadopoulos, P. P. %A Gu, Q. %A Gao, Y. %A Calabro, A. %D 2019 %K dust merger temperature %T Discovery of four cold dusty galaxies at z=3.62-5.85 in the COSMOS field: direct evidence of CMB impact on high-redshift galaxy observables %U http://arxiv.org/abs/1906.00040 %X We report Atacama Large Millimetre Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-Infrared (FIR)/submm observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z=3.62--5.85 using ALMA 3mm line scans, detecting multiple CO and/or CI transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z=5.847. These redshifts are lower than we had expected as these galaxies have substantially colder dust temperatures than most literature sources at z>4. We provide direct evidence that, given their cold spectral energy distributions, CMB plays a significant role biasing their observed Rayleigh-Jeans (RJ) slopes to unlikely steep values and, possibly, reducing their CO fluxes by a factor of two. We recover standard RJ slopes when the CMB contribution is taken into account. High resolution ALMA imaging shows compact morphology and evidence for mergers. This work reveals a population of cold dusty star-forming galaxies that were under-represented in current surveys, and are even colder than typical Main Sequence galaxies at the same redshift. The observed cold dust temperatures could be a result of low star formation efficiency with rapid metal enrichment or, more likely, evidence for optically thick dust continuum in the FIR. High FIR dust optical depth might be a widespread feature of compact starbursts at any redshift.

@misc{jin2019discovery, abstract = {We report Atacama Large Millimetre Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-Infrared (FIR)/submm observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z=3.62--5.85 using ALMA 3mm line scans, detecting multiple CO and/or [CI] transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z=5.847. These redshifts are lower than we had expected as these galaxies have substantially colder dust temperatures than most literature sources at z>4. We provide direct evidence that, given their cold spectral energy distributions, CMB plays a significant role biasing their observed Rayleigh-Jeans (RJ) slopes to unlikely steep values and, possibly, reducing their CO fluxes by a factor of two. We recover standard RJ slopes when the CMB contribution is taken into account. High resolution ALMA imaging shows compact morphology and evidence for mergers. This work reveals a population of cold dusty star-forming galaxies that were under-represented in current surveys, and are even colder than typical Main Sequence galaxies at the same redshift. The observed cold dust temperatures could be a result of low star formation efficiency with rapid metal enrichment or, more likely, evidence for optically thick dust continuum in the FIR. High FIR dust optical depth might be a widespread feature of compact starbursts at any redshift.}, added-at = {2019-06-04T16:24:07.000+0200}, author = {Jin, S. and Daddi, E. and Magdis, G. E. and Liu, D. and Schinnerer, E. and Papadopoulos, P. P. and Gu, Q. and Gao, Y. and Calabro, A.}, biburl = {https://www.bibsonomy.org/bibtex/2c5a37c8de7ac5f253908126c31170576/heh15}, description = {Discovery of four cold dusty galaxies at z=3.62-5.85 in the COSMOS field: direct evidence of CMB impact on high-redshift galaxy observables}, interhash = {25d9318d583ca5859dac570aae2fcb4e}, intrahash = {c5a37c8de7ac5f253908126c31170576}, keywords = {dust merger temperature}, note = {cite arxiv:1906.00040Comment: 13 pages, 8 figures, 4 tables, submitted to ApJ}, timestamp = {2019-06-04T16:24:07.000+0200}, title = {Discovery of four cold dusty galaxies at z=3.62-5.85 in the COSMOS field: direct evidence of CMB impact on high-redshift galaxy observables}, url = {http://arxiv.org/abs/1906.00040}, year = 2019 }