Intae Jung, Swara Ravindranath, Anne E. Jaskot, Henry C. Ferguson, Bethan L. James
We performed spectroscopic analyses of five local compact star-forming galaxies (CSFGs) with extremely high [OIII]/[OII] (O$_{32}$) ratios ($>20$). These targets remarkably share similar properties with high-redshift CIV emitters at $z>6$: high H$beta$ equivalent widths (EWs $>200$AA), extreme O$_{32}$ ratios, low metallicities (12+log(O/H) $lesssim7.8$), low C/O abundances (log(C/O) $<-0.6$), and high ionization conditions (log$U>-2$). The UV spectra were acquired using the Hubble Space Telescope's (HST) Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS). We have identified a wealth of rest-frame UV emission lines (CIV, HeII, OIII], CIII]) in the HST spectra. Notably, all our targets show intense CIV emission lines with rest-frame EWs $>10$AA, indicative of hard ionizing radiation. The rest-frame UV emission line diagnostics disfavor an AGN and could be consistent with significant shock contributions to the source of ionizing radiation. Four of our targets show high CIV/CIII] ratios ($geq1.4$), suggestive of strong Lyman-continuum leakage (LyC escape fraction, $f_{rm esc,LyC}>10$%) from these sources. This is consistent with their Ly$alpha$-inferred LyC escape fractions ($f_{rm esc,LyC}=$ 9 - 31%). We derive relative C/O abundances from our sources, showing log(C/O) values from $-1.12$ to $-0.61$, comparable to those of reionization-era galaxies at $zgtrsim6$. The properties of the CSFGs, particularly their intense CIV emission and high O$_{32}$ ratios, which suggest significant LyC escape fractions, are similar to those of the reionization-era CIV emitters. These similarities reinforce the hypothesis that these CSFGs are the closest analogs of significant contributors to the reionization of the intergalactic medium.
{"title":"Local Analogs of Potential Ionizers of the Intergalactic Medium: Compact Star-Forming Galaxies with Intense CIV $λ$1550 Emission","authors":"Intae Jung, Swara Ravindranath, Anne E. Jaskot, Henry C. Ferguson, Bethan L. James","doi":"arxiv-2409.11460","DOIUrl":"https://doi.org/arxiv-2409.11460","url":null,"abstract":"We performed spectroscopic analyses of five local compact star-forming\u0000galaxies (CSFGs) with extremely high [OIII]/[OII] (O$_{32}$) ratios ($>20$).\u0000These targets remarkably share similar properties with high-redshift CIV\u0000emitters at $z>6$: high H$beta$ equivalent widths (EWs $>200$AA), extreme\u0000O$_{32}$ ratios, low metallicities (12+log(O/H) $lesssim7.8$), low C/O\u0000abundances (log(C/O) $<-0.6$), and high ionization conditions (log$U>-2$). The\u0000UV spectra were acquired using the Hubble Space Telescope's (HST) Cosmic\u0000Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS). We\u0000have identified a wealth of rest-frame UV emission lines (CIV, HeII, OIII],\u0000CIII]) in the HST spectra. Notably, all our targets show intense CIV emission\u0000lines with rest-frame EWs $>10$AA, indicative of hard ionizing radiation. The\u0000rest-frame UV emission line diagnostics disfavor an AGN and could be consistent\u0000with significant shock contributions to the source of ionizing radiation. Four\u0000of our targets show high CIV/CIII] ratios ($geq1.4$), suggestive of strong\u0000Lyman-continuum leakage (LyC escape fraction, $f_{rm esc,LyC}>10$%) from these\u0000sources. This is consistent with their Ly$alpha$-inferred LyC escape fractions\u0000($f_{rm esc,LyC}=$ 9 - 31%). We derive relative C/O abundances from our\u0000sources, showing log(C/O) values from $-1.12$ to $-0.61$, comparable to those\u0000of reionization-era galaxies at $zgtrsim6$. The properties of the CSFGs,\u0000particularly their intense CIV emission and high O$_{32}$ ratios, which suggest\u0000significant LyC escape fractions, are similar to those of the reionization-era\u0000CIV emitters. These similarities reinforce the hypothesis that these CSFGs are\u0000the closest analogs of significant contributors to the reionization of the\u0000intergalactic medium.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quentin Salomé, Philippe Salomé, Benjamin Godard, Pierre Guillard, Antoine Gusdorf
Abridged: We present the first observation of the HCO+(1-0) and HCN(1-0) emission in the northern filaments of Centaurus A with ALMA. HCO+(1-0) is detected in 9 clumps of the Horseshoe complex, with similar velocities as the CO(1-0) emission. Conversely, the HCN(1-0) is not detected and we derive upper limits on the flux. At a resolution of ~40 pc, the line ratio of the velocity-integrated intensities I_HCO+/I_CO varies between 0.03 and 0.08, while I_HCO+/I_HCN is higher than unity with an average lower limit of 1.51. These ratios are significantly higher than what is observed in nearby star-forming galaxies. Moreover, the ratio I_HCO+/I_CO decreases with increasing CO integrated intensity, contrary to what is observed in the star-forming galaxies. This indicates that the HCO+ emission is enhanced and may not arise from dense gas within the Horseshoe complex. This hypothesis is strengthened by the average line ratio I_HCN/I_CO<0.03 which suggests that the gas density is rather low. Using non-LTE, large velocity gradient modelling with RADEX, we explored two possible phases of the gas, that we call "diffuse" and "dense", and are characterised by a significant difference in the HCO+ relative abundance to CO, respectively N_HCO+/N_CO=10^-3 and 3x10^-5. The average CO(1-0) and HCO+(1-0) integrated intensities and the upper limit on HCN(1-0) are compatible with both "diffuse" and "dense" gas. The spectral setup of the present observations also covers the SiO(2-1). While undetected, the upper limit on SiO(2-1) is not compatible with the RADEX predictions for the "dense" gas. We conclude that the 9 molecular clouds detected in HCO+(1-0) are likely dominated by diffuse molecular gas. While the exact origin of the HCO+(1-0) emission remains to be investigated, it is likely related to the energy injection within the molecular gas that prevents gravitational collapse and star formation.
{"title":"Physical conditions in Centaurus A's northern filaments II: Does the HCO$^+$ emission highlight the presence of shocks?","authors":"Quentin Salomé, Philippe Salomé, Benjamin Godard, Pierre Guillard, Antoine Gusdorf","doi":"arxiv-2409.11031","DOIUrl":"https://doi.org/arxiv-2409.11031","url":null,"abstract":"Abridged: We present the first observation of the HCO+(1-0) and HCN(1-0)\u0000emission in the northern filaments of Centaurus A with ALMA. HCO+(1-0) is\u0000detected in 9 clumps of the Horseshoe complex, with similar velocities as the\u0000CO(1-0) emission. Conversely, the HCN(1-0) is not detected and we derive upper\u0000limits on the flux. At a resolution of ~40 pc, the line ratio of the\u0000velocity-integrated intensities I_HCO+/I_CO varies between 0.03 and 0.08, while\u0000I_HCO+/I_HCN is higher than unity with an average lower limit of 1.51. These\u0000ratios are significantly higher than what is observed in nearby star-forming\u0000galaxies. Moreover, the ratio I_HCO+/I_CO decreases with increasing CO\u0000integrated intensity, contrary to what is observed in the star-forming\u0000galaxies. This indicates that the HCO+ emission is enhanced and may not arise\u0000from dense gas within the Horseshoe complex. This hypothesis is strengthened by\u0000the average line ratio I_HCN/I_CO<0.03 which suggests that the gas density is\u0000rather low. Using non-LTE, large velocity gradient modelling with RADEX, we\u0000explored two possible phases of the gas, that we call \"diffuse\" and \"dense\",\u0000and are characterised by a significant difference in the HCO+ relative\u0000abundance to CO, respectively N_HCO+/N_CO=10^-3 and 3x10^-5. The average\u0000CO(1-0) and HCO+(1-0) integrated intensities and the upper limit on HCN(1-0)\u0000are compatible with both \"diffuse\" and \"dense\" gas. The spectral setup of the\u0000present observations also covers the SiO(2-1). While undetected, the upper\u0000limit on SiO(2-1) is not compatible with the RADEX predictions for the \"dense\"\u0000gas. We conclude that the 9 molecular clouds detected in HCO+(1-0) are likely\u0000dominated by diffuse molecular gas. While the exact origin of the HCO+(1-0)\u0000emission remains to be investigated, it is likely related to the energy\u0000injection within the molecular gas that prevents gravitational collapse and\u0000star formation.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The standard $rm Lambda$CDM cosmological model predicts that a large amount of diffuse neutral hydrogen distributes in cosmic filaments, which could be mapped through Lyman-alpha (Ly$alpha$) emission observations. We use the hydrodynamical simulation Illustris-TNG50 to investigate the evolution of surface brightness and detectability of neutral hydrogen in cosmic filaments across redshifts $z=2-5$. While the HI column density of cosmic filaments decreases with redshift, due to the rising temperature with cosmic time in filaments, the surface brightness of Ly$alpha$ emission in filaments is brighter at lower redshifts, suggesting that the detection of cosmic filaments is more feasible at lower redshifts. However, most of the Ly$alpha$ emission from cosmic filaments is around $10^{-21}$ $rm erg s^{-1}cm^{-2}arsec^{-2}$, making it extremely challenging to detect with current observational instruments. We further generate mock images using the Multi-Unit Spectroscopic Explorer (MUSE) spectrograph installed on both the Very Large Telescope (VLT) and the upcoming Extremely Large Telescope (ELT). Our finding indicates that while the VLT can only detect filamentary structures made of dense gas in galactic centers, the ELT is expected to reveal much finer filamentary structures from diffuse neutral hydrogen outside of galaxies. Compared to the VLT, both the number density and the longest length of filaments are greatly boosted with the ELT. Hence the forthcoming ELT is highly promising to provide a clearer view of cosmic filaments in Ly$alpha$ emission.
{"title":"Prospects for detecting cosmic filaments in Lyman-alpha emission across redshifts $z=2-5$","authors":"Yizhou Liu, Liang Gao, Shihong Liao, Kai Zhu","doi":"arxiv-2409.11088","DOIUrl":"https://doi.org/arxiv-2409.11088","url":null,"abstract":"The standard $rm Lambda$CDM cosmological model predicts that a large amount\u0000of diffuse neutral hydrogen distributes in cosmic filaments, which could be\u0000mapped through Lyman-alpha (Ly$alpha$) emission observations. We use the\u0000hydrodynamical simulation Illustris-TNG50 to investigate the evolution of\u0000surface brightness and detectability of neutral hydrogen in cosmic filaments\u0000across redshifts $z=2-5$. While the HI column density of cosmic filaments\u0000decreases with redshift, due to the rising temperature with cosmic time in\u0000filaments, the surface brightness of Ly$alpha$ emission in filaments is\u0000brighter at lower redshifts, suggesting that the detection of cosmic filaments\u0000is more feasible at lower redshifts. However, most of the Ly$alpha$ emission\u0000from cosmic filaments is around $10^{-21}$ $rm erg s^{-1}cm^{-2}arsec^{-2}$,\u0000making it extremely challenging to detect with current observational\u0000instruments. We further generate mock images using the Multi-Unit Spectroscopic\u0000Explorer (MUSE) spectrograph installed on both the Very Large Telescope (VLT)\u0000and the upcoming Extremely Large Telescope (ELT). Our finding indicates that\u0000while the VLT can only detect filamentary structures made of dense gas in\u0000galactic centers, the ELT is expected to reveal much finer filamentary\u0000structures from diffuse neutral hydrogen outside of galaxies. Compared to the\u0000VLT, both the number density and the longest length of filaments are greatly\u0000boosted with the ELT. Hence the forthcoming ELT is highly promising to provide\u0000a clearer view of cosmic filaments in Ly$alpha$ emission.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mathias Lipka, Jens Thomas, Roberto Saglia, Ralf Bender, Maximilian Fabricius, Christian Partmann
We analyze the dark matter (DM) halos of a sample of dwarf Ellitpicals (dE) and discuss cosmological and evolutionary implications. Using orbit modeling we recover their density slopes and, for the first time, the halo flattening. We find the `cusp-core' tension is mild, on average dEs have central slopes slightly below the Navarro Frenk White (NFW) predictions. However, the measured flattenings are still more spherical than cosmological simulations predict. Unlike brighter ETGs the total density slopes of dEs are shallower, and their average DM density does not follow their scaling relation with luminosity. Conversely, dE halos are denser and the densities steeper than in LTGs. We find average DM density and slope are strongly correlated with the environment and moderately with the angular momentum. Central, non-rotating dEs have dense and cuspy halos, whereas rotating dEs in Virgo's outskirts are more cored and less dense. This can be explained by a delayed formation of the dEs in the cluster outskirts, or alternatively, by the accumulated baryonic feedback the dEs in the outskirts have experienced during their very different star formation history. Our results suggest halo profiles are not universal (they depend on assembly conditions) and they evolve only mildly due to internal feedback. We conclude dEs in the local Universe have assembled at a higher redshift than local spirals. In these extreme conditions (e.g. star-formation, halo assembly) were very different, suggesting no new dEs are formed at present.
{"title":"The VIRUS-dE Survey II: Cuspy and round halos in dwarf ellipticals -- A result of early assembly?","authors":"Mathias Lipka, Jens Thomas, Roberto Saglia, Ralf Bender, Maximilian Fabricius, Christian Partmann","doi":"arxiv-2409.11458","DOIUrl":"https://doi.org/arxiv-2409.11458","url":null,"abstract":"We analyze the dark matter (DM) halos of a sample of dwarf Ellitpicals (dE)\u0000and discuss cosmological and evolutionary implications. Using orbit modeling we\u0000recover their density slopes and, for the first time, the halo flattening. We\u0000find the `cusp-core' tension is mild, on average dEs have central slopes\u0000slightly below the Navarro Frenk White (NFW) predictions. However, the measured\u0000flattenings are still more spherical than cosmological simulations predict.\u0000Unlike brighter ETGs the total density slopes of dEs are shallower, and their\u0000average DM density does not follow their scaling relation with luminosity.\u0000Conversely, dE halos are denser and the densities steeper than in LTGs. We find\u0000average DM density and slope are strongly correlated with the environment and\u0000moderately with the angular momentum. Central, non-rotating dEs have dense and\u0000cuspy halos, whereas rotating dEs in Virgo's outskirts are more cored and less\u0000dense. This can be explained by a delayed formation of the dEs in the cluster\u0000outskirts, or alternatively, by the accumulated baryonic feedback the dEs in\u0000the outskirts have experienced during their very different star formation\u0000history. Our results suggest halo profiles are not universal (they depend on\u0000assembly conditions) and they evolve only mildly due to internal feedback. We\u0000conclude dEs in the local Universe have assembled at a higher redshift than\u0000local spirals. In these extreme conditions (e.g. star-formation, halo assembly)\u0000were very different, suggesting no new dEs are formed at present.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marco A. Canossa-Gosteinski, Ana L. Chies-Santos, Cristina Furlanetto, Charles J. Bonatto, Rodrigo Flores-Freitas, William Schoenell, Michael A. Beasley, Roderik Overzier, Basilio X. Santiago, Adriano Pieres, Emílio J. B. Zanatta, Karla A. Alamo-Martinez, Eduardo Balbinot, Anna B. A. Queiroz, Alan Alves-Brito
Understanding faint dwarf galaxies is fundamental to the development of a robust theory of galaxy formation on small scales. Since the discovery of a population of ultra diffuse galaxies (UDGs) rich in globular clusters (GCs) in Coma, an increasing number of studies on low surface brightness dwarf galaxies (LSBds) have been published in recent years. The most massive LSBds have been observed predominantly in groups and clusters, with properties displaying dependence on the environment. In this work, we use deep DECam imaging to systematically identify LSBds and their GC populations around the low-density environment of NGC 3115. We carefully analyse the structure and morphology of 24 candidates, 18 of which are reported for the first time. Most candidates exhibit red colours suggesting a connection between their colour and distance to NGC 3115. We followed up with Gemini GMOS imaging 9 LSBds to properly identify their GC populations. We derive lower limits for the number of GCs associated with each galaxy. Our analysis reveals that they occur around of the same loci of Fornax LSB dwarf GC systems. The relationship between the number of GCs and total mass provides a tool in which, by counting the GCs in these galaxies, we estimate an upper limit for the total mass of these LSB dwarfs, obtaining the mean value of $sim 3.3times10^{10}$ M$_{odot}$. Our results align with expectations for dwarf-sized galaxies, particularly regarding the distribution and specific frequency of their GC systems.
{"title":"Low surface brightness dwarf galaxies and their globular cluster populations around the low-density environment of our closest S0 NGC3115","authors":"Marco A. Canossa-Gosteinski, Ana L. Chies-Santos, Cristina Furlanetto, Charles J. Bonatto, Rodrigo Flores-Freitas, William Schoenell, Michael A. Beasley, Roderik Overzier, Basilio X. Santiago, Adriano Pieres, Emílio J. B. Zanatta, Karla A. Alamo-Martinez, Eduardo Balbinot, Anna B. A. Queiroz, Alan Alves-Brito","doi":"arxiv-2409.10205","DOIUrl":"https://doi.org/arxiv-2409.10205","url":null,"abstract":"Understanding faint dwarf galaxies is fundamental to the development of a\u0000robust theory of galaxy formation on small scales. Since the discovery of a\u0000population of ultra diffuse galaxies (UDGs) rich in globular clusters (GCs) in\u0000Coma, an increasing number of studies on low surface brightness dwarf galaxies\u0000(LSBds) have been published in recent years. The most massive LSBds have been\u0000observed predominantly in groups and clusters, with properties displaying\u0000dependence on the environment. In this work, we use deep DECam imaging to\u0000systematically identify LSBds and their GC populations around the low-density\u0000environment of NGC 3115. We carefully analyse the structure and morphology of\u000024 candidates, 18 of which are reported for the first time. Most candidates\u0000exhibit red colours suggesting a connection between their colour and distance\u0000to NGC 3115. We followed up with Gemini GMOS imaging 9 LSBds to properly\u0000identify their GC populations. We derive lower limits for the number of GCs\u0000associated with each galaxy. Our analysis reveals that they occur around of the\u0000same loci of Fornax LSB dwarf GC systems. The relationship between the number\u0000of GCs and total mass provides a tool in which, by counting the GCs in these\u0000galaxies, we estimate an upper limit for the total mass of these LSB dwarfs,\u0000obtaining the mean value of $sim 3.3times10^{10}$ M$_{odot}$. Our results\u0000align with expectations for dwarf-sized galaxies, particularly regarding the\u0000distribution and specific frequency of their GC systems.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"199 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Florent Renaud, Bridget Ratcliffe, Ivan Minchev, Misha Haywood, Paola Di Matteo, Oscar Agertz, Alessandro B. Romeo
We analyze the evolution of the radial profiles and the azimuthal variations of the stellar metallicities from the Vintergatan simulation of a Milky Way-like galaxy. We find that negative gradients exist as soon as the disk settles at high redshift, and are maintained throughout the long term evolution of the galaxy, including during major merger events. The inside-out growth of the disk and an overall outward radial migration tend to flatten these gradients in time. Major merger events only have a moderate and short-lived imprint on the [Fe/H] distributions with almost no radial dependence. The reason lies in the timescale for enrichment in Fe being significantly longer than the duration of the starbursts episodes, themselves slower than dynamical mixing during typical interactions. It results that signatures of major mergers become undetectable in [Fe/H] only a few Myr after pericenter passages. We note that considering other tracers like the warm interstellar medium, or monitoring the evolution of the metallicity gradient as a single value instead of a radial full profile could lead to different interpretations, and warn against an oversimplification of this complex problem.
{"title":"Effects of secular growth and mergers on the evolution of metallicity gradients and azimuthal variations in a Milky Way-like galaxy","authors":"Florent Renaud, Bridget Ratcliffe, Ivan Minchev, Misha Haywood, Paola Di Matteo, Oscar Agertz, Alessandro B. Romeo","doi":"arxiv-2409.10598","DOIUrl":"https://doi.org/arxiv-2409.10598","url":null,"abstract":"We analyze the evolution of the radial profiles and the azimuthal variations\u0000of the stellar metallicities from the Vintergatan simulation of a Milky\u0000Way-like galaxy. We find that negative gradients exist as soon as the disk\u0000settles at high redshift, and are maintained throughout the long term evolution\u0000of the galaxy, including during major merger events. The inside-out growth of\u0000the disk and an overall outward radial migration tend to flatten these\u0000gradients in time. Major merger events only have a moderate and short-lived\u0000imprint on the [Fe/H] distributions with almost no radial dependence. The\u0000reason lies in the timescale for enrichment in Fe being significantly longer\u0000than the duration of the starbursts episodes, themselves slower than dynamical\u0000mixing during typical interactions. It results that signatures of major mergers\u0000become undetectable in [Fe/H] only a few Myr after pericenter passages. We note\u0000that considering other tracers like the warm interstellar medium, or monitoring\u0000the evolution of the metallicity gradient as a single value instead of a radial\u0000full profile could lead to different interpretations, and warn against an\u0000oversimplification of this complex problem.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Trofimova, I. Zinchenko, P. Zemlyanukha, M. Thomasson
The present survey represents a continuation of our study of high mass star forming regions in the lines of deuterated molecules, the first results of which were published in Trofimova et al. (2020). This paper presents the results of observations of 50 objects in the line of ortho modification of singly deuterated ammonia NH$_2$D $1_{11}^s - 1_{01}^a$ at frequency 85.9 GHz, carried out with the 20-m radio telescope of the Onsala Space Observatory (Sweden). This line is detected in 29 sources. The analysis of obtained data, as well as the fact that gas density in the investigated sources, according to independent estimates, is significantly lower than the critical density for this NH$_2$D transition, indicate non-LTE excitation of NH$_2$D. Based on non-LTE modeling, estimates of the relative content of the NH$_2$D molecule and the degree of deuterium enrichment were obtained, and the dependencies of these parameters on temperature and velocity dispersion were analyzed with and without taking into account detection limits assuming the same gas density in all sources. An anti-correlation between the NH$_2$D relative abundances and the kinetic temperature is revealed in the temperature range 15-50K. At the same time, significant decrease in the ratio of the NH$_2$D/NH$_3$ abundances with increasing temperature, predicted by the available chemical models, is not observed under the adopted assumptions. An anti-correlation was also revealed between the relative content of the main isotopologue of ammonia NH$_3$ and the velocity dispersion, while no statistically significant correlation with the kinetic temperature of sources in the same temperature range was found.
{"title":"A Survey Of High Mass Star Forming Regions In The Line Of Singly Deuterated Ammonia NH2D","authors":"E. Trofimova, I. Zinchenko, P. Zemlyanukha, M. Thomasson","doi":"arxiv-2409.10199","DOIUrl":"https://doi.org/arxiv-2409.10199","url":null,"abstract":"The present survey represents a continuation of our study of high mass star\u0000forming regions in the lines of deuterated molecules, the first results of\u0000which were published in Trofimova et al. (2020). This paper presents the\u0000results of observations of 50 objects in the line of ortho modification of\u0000singly deuterated ammonia NH$_2$D $1_{11}^s - 1_{01}^a$ at frequency 85.9 GHz,\u0000carried out with the 20-m radio telescope of the Onsala Space Observatory\u0000(Sweden). This line is detected in 29 sources. The analysis of obtained data,\u0000as well as the fact that gas density in the investigated sources, according to\u0000independent estimates, is significantly lower than the critical density for\u0000this NH$_2$D transition, indicate non-LTE excitation of NH$_2$D. Based on\u0000non-LTE modeling, estimates of the relative content of the NH$_2$D molecule and\u0000the degree of deuterium enrichment were obtained, and the dependencies of these\u0000parameters on temperature and velocity dispersion were analyzed with and\u0000without taking into account detection limits assuming the same gas density in\u0000all sources. An anti-correlation between the NH$_2$D relative abundances and\u0000the kinetic temperature is revealed in the temperature range 15-50K. At the\u0000same time, significant decrease in the ratio of the NH$_2$D/NH$_3$ abundances\u0000with increasing temperature, predicted by the available chemical models, is not\u0000observed under the adopted assumptions. An anti-correlation was also revealed\u0000between the relative content of the main isotopologue of ammonia NH$_3$ and the\u0000velocity dispersion, while no statistically significant correlation with the\u0000kinetic temperature of sources in the same temperature range was found.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Solhaug, H. -W. Chen, M. C. Chen, F. Zahedy, M. Gronke, M. -J. Hamel-Bravo, M. B. Bayliss, M. D. Gladders, S. López, N. Tejos
The hydrogen Lyman-alpha (Lya) emission line, the brightest spectral feature of a photoionized gas, is considered an indirect tracer of the escape of Lyman continuum (LyC) photons, particularly when the intergalactic medium is too opaque for direct detection. However, resonant scattering complicates interpreting the empirical properties of Lya photons, necessitating radiative transfer simulations to capture their strong coupling with underlying gas kinematics. In this study, we leverage the exceptional spatial resolution from strong gravitational lensing to investigate the connection between Lya line profiles and LyC leakage on scales of a few 100 pc in the Sunburst Arc galaxy at $zsim2.37$. New optical echelle spectra obtained using Magellan MIKE show that both the LyC leaking and non-leaking regions exhibit a classic double-peak Lya feature with an enhanced red peak, indicating outflows at multiple locations in the galaxy. Both regions also show a central Gaussian peak atop the double peaks, indicating directly escaped Lya photons independent of LyC leakage. We introduce a machine learning-based method for emulating Lya simulations to quantify intrinsic dynamics ($sigma_{mathrm{int}}$), neutral hydrogen column density ($N_{mathrm{HI}}$), outflow velocity ($v_{mathrm{exp}}$), and effective temperature ($T$) across continuous parameter spaces. By comparing the spatially and spectrally resolved Lya lines in Sunburst, we argue that the directly escaped Lya photons originate in a volume-filling, warm ionized medium spanning $sim1$ kpc, while the LyC leakage is confined to regions of $lesssim200$ pc. These sub-kpc variations in Lya profiles highlight the complexity of interpreting integrated properties in the presence of inhomogeneous mixtures of gas and young stars, emphasizing the need for spatially and spectrally resolved observations of distant galaxies.
{"title":"Deciphering spatially resolved Lyman-alpha profiles in reionization analogs: the Sunburst Arc at cosmic noon","authors":"E. Solhaug, H. -W. Chen, M. C. Chen, F. Zahedy, M. Gronke, M. -J. Hamel-Bravo, M. B. Bayliss, M. D. Gladders, S. López, N. Tejos","doi":"arxiv-2409.10604","DOIUrl":"https://doi.org/arxiv-2409.10604","url":null,"abstract":"The hydrogen Lyman-alpha (Lya) emission line, the brightest spectral feature\u0000of a photoionized gas, is considered an indirect tracer of the escape of Lyman\u0000continuum (LyC) photons, particularly when the intergalactic medium is too\u0000opaque for direct detection. However, resonant scattering complicates\u0000interpreting the empirical properties of Lya photons, necessitating radiative\u0000transfer simulations to capture their strong coupling with underlying gas\u0000kinematics. In this study, we leverage the exceptional spatial resolution from\u0000strong gravitational lensing to investigate the connection between Lya line\u0000profiles and LyC leakage on scales of a few 100 pc in the Sunburst Arc galaxy\u0000at $zsim2.37$. New optical echelle spectra obtained using Magellan MIKE show\u0000that both the LyC leaking and non-leaking regions exhibit a classic double-peak\u0000Lya feature with an enhanced red peak, indicating outflows at multiple\u0000locations in the galaxy. Both regions also show a central Gaussian peak atop\u0000the double peaks, indicating directly escaped Lya photons independent of LyC\u0000leakage. We introduce a machine learning-based method for emulating Lya\u0000simulations to quantify intrinsic dynamics ($sigma_{mathrm{int}}$), neutral\u0000hydrogen column density ($N_{mathrm{HI}}$), outflow velocity\u0000($v_{mathrm{exp}}$), and effective temperature ($T$) across continuous\u0000parameter spaces. By comparing the spatially and spectrally resolved Lya lines\u0000in Sunburst, we argue that the directly escaped Lya photons originate in a\u0000volume-filling, warm ionized medium spanning $sim1$ kpc, while the LyC leakage\u0000is confined to regions of $lesssim200$ pc. These sub-kpc variations in Lya\u0000profiles highlight the complexity of interpreting integrated properties in the\u0000presence of inhomogeneous mixtures of gas and young stars, emphasizing the need\u0000for spatially and spectrally resolved observations of distant galaxies.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"189 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the morphology of galaxies is a critical aspect of astrophysics research, providing insight into the formation, evolution, and physical properties of these vast cosmic structures. Various observational and computational methods have been developed to quantify galaxy morphology, and with the advent of large galaxy simulations, the need for automated and effective classification methods has become increasingly important. This paper investigates the use of Principal Component Analysis (PCA) as an interpretable dimensionality reduction algorithm for galaxy morphology using the IllustrisTNG cosmological simulation dataset with the aim of developing a generative model for galaxies. We first generate a dataset of 2D images and 3D cubes of galaxies from the IllustrisTNG simulation, focusing on the mass, metallicity, and stellar age distribution of each galaxy. PCA is then applied to this data, transforming it into a lower-dimensional image space, where closeness of data points corresponds to morphological similarity. We find that PCA can effectively capture the key morphological features of galaxies, with a significant proportion of the variance in the data being explained by a small number of components. With our method we achieve a dimensionality reduction by a factor of $sim200$ for 2D images and $sim3650$ for 3D cubes at a reconstruction accuracy below five percent. Our results illustrate the potential of PCA in compressing large cosmological simulations into an interpretable generative model for galaxies that can easily be used in various downstream tasks such as galaxy classification and analysis.
{"title":"MEGS: Morphological Evaluation of Galactic Structure","authors":"Ufuk Çakır, Tobias Buck","doi":"arxiv-2409.10346","DOIUrl":"https://doi.org/arxiv-2409.10346","url":null,"abstract":"Understanding the morphology of galaxies is a critical aspect of astrophysics\u0000research, providing insight into the formation, evolution, and physical\u0000properties of these vast cosmic structures. Various observational and\u0000computational methods have been developed to quantify galaxy morphology, and\u0000with the advent of large galaxy simulations, the need for automated and\u0000effective classification methods has become increasingly important. This paper\u0000investigates the use of Principal Component Analysis (PCA) as an interpretable\u0000dimensionality reduction algorithm for galaxy morphology using the IllustrisTNG\u0000cosmological simulation dataset with the aim of developing a generative model\u0000for galaxies. We first generate a dataset of 2D images and 3D cubes of galaxies\u0000from the IllustrisTNG simulation, focusing on the mass, metallicity, and\u0000stellar age distribution of each galaxy. PCA is then applied to this data,\u0000transforming it into a lower-dimensional image space, where closeness of data\u0000points corresponds to morphological similarity. We find that PCA can\u0000effectively capture the key morphological features of galaxies, with a\u0000significant proportion of the variance in the data being explained by a small\u0000number of components. With our method we achieve a dimensionality reduction by\u0000a factor of $sim200$ for 2D images and $sim3650$ for 3D cubes at a\u0000reconstruction accuracy below five percent. Our results illustrate the\u0000potential of PCA in compressing large cosmological simulations into an\u0000interpretable generative model for galaxies that can easily be used in various\u0000downstream tasks such as galaxy classification and analysis.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present new results from the ASTRID simulation from $z=3$ to $z=0.5$, covering the epoch of cosmic noon. The galaxy stellar mass function, as well as the black hole mass and luminosity functions in ASTRID, exhibit good agreement with recent observational constraints. We study the $M_{rm BH}$-$M_*$ scaling relation and its connections to AGN luminosity, galaxy color, and star formation rate, demonstrating that AGN feedback plays a crucial role in the quenching of massive galaxies ($M_*>10^{10.5} M_{odot}$). Although AGN feedback suppresses star formation through quenching, AGN-host galaxies still exhibit statistically higher levels of star formation compared to inactive ones, due to the positive correlation between AGN activity and star formation, both fueled by a shared gas reservoir. The fraction of quiescent galaxies in ASTRID increases with both galaxy mass and redshift evolution, aligning well with observational trends. We find that different quenching mechanisms can leave distinct morphological imprints on quenched galaxies. Massive, compact quiescent galaxies typically experience shorter quenching timescales, have younger central regions, and host overmassive black holes. This is usually due to a compaction-like quenching mechanism that funnels gas into the galaxy center, leading to starbursts and triggering AGN kinetic feedback. In contrast, quiescent galaxies with more diffuse morphologies generally experience `inside-out' quenching, which is characterized by older central regions compared to the outskirts. These galaxies typically experience longer quenching timescales due to quenching processes operating on a larger halo scale, which gradually deplete the galactic star-forming gas. Data of the astrid simulation down to $z=0.5$ is available at url{https://astrid.psc.edu}.
{"title":"The Astrid Simulation: Evolution of black holes and galaxies to z=0.5 and different evolution pathways for galaxy quenching","authors":"Yueying Ni, Nianyi Chen, Yihao Zhou, Minjung Park, Yanhui Yang, Tiziana DiMatteo, Simeon Bird, Rupert Croft","doi":"arxiv-2409.10666","DOIUrl":"https://doi.org/arxiv-2409.10666","url":null,"abstract":"We present new results from the ASTRID simulation from $z=3$ to $z=0.5$,\u0000covering the epoch of cosmic noon. The galaxy stellar mass function, as well as\u0000the black hole mass and luminosity functions in ASTRID, exhibit good agreement\u0000with recent observational constraints. We study the $M_{rm BH}$-$M_*$ scaling\u0000relation and its connections to AGN luminosity, galaxy color, and star\u0000formation rate, demonstrating that AGN feedback plays a crucial role in the\u0000quenching of massive galaxies ($M_*>10^{10.5} M_{odot}$). Although AGN\u0000feedback suppresses star formation through quenching, AGN-host galaxies still\u0000exhibit statistically higher levels of star formation compared to inactive\u0000ones, due to the positive correlation between AGN activity and star formation,\u0000both fueled by a shared gas reservoir. The fraction of quiescent galaxies in\u0000ASTRID increases with both galaxy mass and redshift evolution, aligning well\u0000with observational trends. We find that different quenching mechanisms can\u0000leave distinct morphological imprints on quenched galaxies. Massive, compact\u0000quiescent galaxies typically experience shorter quenching timescales, have\u0000younger central regions, and host overmassive black holes. This is usually due\u0000to a compaction-like quenching mechanism that funnels gas into the galaxy\u0000center, leading to starbursts and triggering AGN kinetic feedback. In contrast,\u0000quiescent galaxies with more diffuse morphologies generally experience\u0000`inside-out' quenching, which is characterized by older central regions\u0000compared to the outskirts. These galaxies typically experience longer quenching\u0000timescales due to quenching processes operating on a larger halo scale, which\u0000gradually deplete the galactic star-forming gas. Data of the astrid simulation\u0000down to $z=0.5$ is available at url{https://astrid.psc.edu}.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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