{"id":{"repo_id":"texas","oai_identifier":"oai:repositories.lib.utexas.edu:2152/72441"},"canonical_url":"https://search.dev.ndltd.org/etd/texas/oai:repositories.lib.utexas.edu:2152/72441","repository":{"repo_id":"texas","name":"University of Texas","base_url":"https://repositories.lib.utexas.edu/server/oai/request"},"display":{"title":"No evidence for millimeter continuum source overdensities in the environments of z [greater than approximately] 6 quasars","abstract":"Bright high-redshift quasars (z > 6), hosting supermassive black holes (M [subscript BH] > 10⁸M [subscript circled dot]), are expected to reside in massive host galaxies embedded within some of the earliest, most massive galaxy overdensities. We analyze 1.2mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess continuum emission as evidence for early protoclusters. We compare the detection rates of continuum sources at [greater than or equal to] 5σ significance in the fields surrounding the quasars (A [subscript eff] = 4.3 arcmin²) with millimeter number counts in blank field surveys. We discover 15 sources in the fields (excluding the quasars themselves), corresponding to an overdensity δ [subscript gal] [triple bar] (N [subscript gal] – N [subscript exp]) / N [subscript exp] = -0.07 ± 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [CII] overdensities found on the same scales to similarly-selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line of sight volume probed by a continuum survey will wash out a true overdensity signal.","abstract_html":"Bright high-redshift quasars (z > 6), hosting supermassive black holes (M [subscript BH] > 10⁸M [subscript circled dot]), are expected to reside in massive host galaxies embedded within some of the earliest, most massive galaxy overdensities. We analyze 1.2mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess continuum emission as evidence for early protoclusters. We compare the detection rates of continuum sources at [greater than or equal to] 5σ significance in the fields surrounding the quasars (A [subscript eff] = 4.3 arcmin²) with millimeter number counts in blank field surveys. We discover 15 sources in the fields (excluding the quasars themselves), corresponding to an overdensity δ [subscript gal] [triple bar] (N [subscript gal] – N [subscript exp]) / N [subscript exp] = -0.07 ± 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [CII] overdensities found on the same scales to similarly-selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line of sight volume probed by a continuum survey will wash out a true overdensity signal.","abstract_has_math":false,"creators":["Champagne, Jaclyn Bradli"],"institution":"The University of Texas at Austin","degree_name":"Master of Arts","degree_level":"Masters","degree_discipline":"Astronomy","degree_department":null,"school":null,"contributors":[],"advisors":["Casey, Caitlin M."],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-05","date_published":"2018-09-05","updated_at":"2026-07-24T05:00:54Z","subjects":["Galaxy clusters","Dust continuum","Carbon","Protoclusters","Quasars","Overdensity","Millimeter astronomy","ALMA"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["doi:10.15781/T25M62T6K"],"render_values":[{"text":"doi:10.15781/T25M62T6K","href":"https://doi.org/10.15781/T25M62T6K","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2152/72441","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Casey, Caitlin M."]},{"key":"dc:creator","label":"Author","values":["Champagne, Jaclyn Bradli"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-01-18T22:15:57Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2019-01-18T22:15:57Z"]},{"key":"dc:date.issued","label":"Date","values":["2018-09-05"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Astronomy"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Arts"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["The University of Texas at Austin"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Galaxy clusters","Dust continuum","Carbon","Protoclusters","Quasars","Overdensity","Millimeter astronomy","ALMA"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["doi:10.15781/T25M62T6K"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/2152/72441"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Bright high-redshift quasars (z > 6), hosting supermassive black holes (M [subscript BH] > 10⁸M [subscript circled dot]), are expected to reside in massive host galaxies embedded within some of the earliest, most massive galaxy overdensities. We analyze 1.2mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess continuum emission as evidence for early protoclusters. We compare the detection rates of continuum sources at [greater than or equal to] 5σ significance in the fields surrounding the quasars (A [subscript eff] = 4.3 arcmin²) with millimeter number counts in blank field surveys. We discover 15 sources in the fields (excluding the quasars themselves), corresponding to an overdensity δ [subscript gal] [triple bar] (N [subscript gal] – N [subscript exp]) / N [subscript exp] = -0.07 ± 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [CII] overdensities found on the same scales to similarly-selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line of sight volume probed by a continuum survey will wash out a true overdensity signal."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["No evidence for millimeter continuum source overdensities in the environments of z [greater than approximately] 6 quasars"]}]}],"canonical_facts":{"dc:contributor.advisor":["Casey, Caitlin M."],"dc:creator":["Champagne, Jaclyn Bradli"],"dc:date.accessioned":["2019-01-18T22:15:57Z"],"dc:date.available":["2019-01-18T22:15:57Z"],"dc:date.issued":["2018-09-05"],"dc:description.abstract":["Bright high-redshift quasars (z > 6), hosting supermassive black holes (M [subscript BH] > 10⁸M [subscript circled dot]), are expected to reside in massive host galaxies embedded within some of the earliest, most massive galaxy overdensities. We analyze 1.2mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess continuum emission as evidence for early protoclusters. We compare the detection rates of continuum sources at [greater than or equal to] 5σ significance in the fields surrounding the quasars (A [subscript eff] = 4.3 arcmin²) with millimeter number counts in blank field surveys. We discover 15 sources in the fields (excluding the quasars themselves), corresponding to an overdensity δ [subscript gal] [triple bar] (N [subscript gal] – N [subscript exp]) / N [subscript exp] = -0.07 ± 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [CII] overdensities found on the same scales to similarly-selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line of sight volume probed by a continuum survey will wash out a true overdensity signal."],"dc:format.mimetype":["application/pdf"],"dc:identifier":["doi:10.15781/T25M62T6K"],"dc:identifier.uri":["http://hdl.handle.net/2152/72441"],"dc:language.iso":["en"],"dc:subject":["Galaxy clusters","Dust continuum","Carbon","Protoclusters","Quasars","Overdensity","Millimeter astronomy","ALMA"],"dc:title":["No evidence for millimeter continuum source overdensities in the environments of z [greater than approximately] 6 quasars"],"dc:type":["Thesis"],"thesis:degree_discipline":["Astronomy"],"thesis:degree_level":["Masters"],"thesis:degree_name":["Master of Arts"],"thesis:institution_name":["The University of Texas at Austin"]},"updated_at":"2026-07-24T05:00:54Z"}