The James Webb Space Telescope (JWST) has uncovered low-luminosity active galactic nuclei (AGNs) at high redshifts of $zgtrsim 4-7$, powered by accreting black holes (BHs) with masses of $sim 10^{6-8}~M_odot$. These AGN populations are considered crucial for understanding early BH assembly and coevolution with their host galaxies. One remarkable distinction of these JWST-identified AGNs, compared to their low-redshift counterparts, is that at least $sim 20%$ of them present H$alpha$ and/or H$beta$ absorption, which must be associated with extremely dense ($gtrsim 10^9$ cm$^{-3}$) gas along the line of sight. These Balmer absorption features unavoidably imply the presence of a Balmer break caused by the same dense gas. In this Letter, we quantitatively demonstrate that a Balmer-break feature can form in AGN spectra without stellar components, when the accretion disk is heavily embedded in dense neutral gas clumps with densities of $sim 10^{9-11}$ cm$^{-3}$, where hydrogen atoms are collisionally excited to the $n=2$ states and effectively absorb the AGN continuum at the bluer side of the Balmer limit. The non-stellar origin of a Balmer break offers a potential solution to the large stellar masses and densities inferred for little red dots (LRDs) when assuming that their continuum is primarily due to stellar light. Our calculations of hydrogen-level populations indicate that the observed Balmer absorption blueshifted by a few hundreds km s$^{-1}$ suggests the presence of dense outflows at parsec scales in the nucleus. The outflow rate likely exceeds the Eddington accretion rate, driven by powerful radiation from a super-Eddington accretion disk. Other spectral features such as higher equivalent widths of broad H$alpha$ emission and presence of OI lines observed in high-redshift AGNs including LRDs align with the predicted signatures of a dense super-Eddington accretion disk.
{"title":"Extremely Dense Gas around Little Red Dots and High-redshift AGNs: A Non-stellar Origin of the Balmer Break and Absorption Features","authors":"Kohei Inayoshi, Roberto Maiolino","doi":"arxiv-2409.07805","DOIUrl":"https://doi.org/arxiv-2409.07805","url":null,"abstract":"The James Webb Space Telescope (JWST) has uncovered low-luminosity active\u0000galactic nuclei (AGNs) at high redshifts of $zgtrsim 4-7$, powered by\u0000accreting black holes (BHs) with masses of $sim 10^{6-8}~M_odot$. These AGN\u0000populations are considered crucial for understanding early BH assembly and\u0000coevolution with their host galaxies. One remarkable distinction of these\u0000JWST-identified AGNs, compared to their low-redshift counterparts, is that at\u0000least $sim 20%$ of them present H$alpha$ and/or H$beta$ absorption, which\u0000must be associated with extremely dense ($gtrsim 10^9$ cm$^{-3}$) gas along\u0000the line of sight. These Balmer absorption features unavoidably imply the\u0000presence of a Balmer break caused by the same dense gas. In this Letter, we\u0000quantitatively demonstrate that a Balmer-break feature can form in AGN spectra\u0000without stellar components, when the accretion disk is heavily embedded in\u0000dense neutral gas clumps with densities of $sim 10^{9-11}$ cm$^{-3}$, where\u0000hydrogen atoms are collisionally excited to the $n=2$ states and effectively\u0000absorb the AGN continuum at the bluer side of the Balmer limit. The non-stellar\u0000origin of a Balmer break offers a potential solution to the large stellar\u0000masses and densities inferred for little red dots (LRDs) when assuming that\u0000their continuum is primarily due to stellar light. Our calculations of\u0000hydrogen-level populations indicate that the observed Balmer absorption\u0000blueshifted by a few hundreds km s$^{-1}$ suggests the presence of dense\u0000outflows at parsec scales in the nucleus. The outflow rate likely exceeds the\u0000Eddington accretion rate, driven by powerful radiation from a super-Eddington\u0000accretion disk. Other spectral features such as higher equivalent widths of\u0000broad H$alpha$ emission and presence of OI lines observed in high-redshift\u0000AGNs including LRDs align with the predicted signatures of a dense\u0000super-Eddington accretion disk.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195411","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}
Chloë E. Benton, Erica J. Nelson, Tim B. Miller, Rachel Bezanson, Justus Gibson, Abigail I Hartley, Marco Martorano, Sedona H. Price, Katherine A. Suess, Arjen van der Wel, Pieter van Dokkum, John R. Weaver, Katherine E. Whitaker
Hubble Space Telescope imaging shows that most star-forming galaxies at cosmic noon -- the peak of cosmic star formation history -- appear disk-dominated, leaving the origin of the dense cores in their quiescent descendants unclear. With the James Webb Space Telescope's (JWST) high-resolution imaging to 5 {mu}m, we can now map the rest-frame near-infrared emission, a much closer proxy for stellar mass distribution, in these massive galaxies. We selected 70 star-forming galaxies with 10$<$log(M)$<$12 and 1.5$<$z$<$3 in the CEERS survey and compare their morphologies in the rest-frame optical to those in the rest-frame near-IR. While the bulk of these galaxies are disk-dominated in 1.5 {mu}m (rest-frame optical) imaging, they appear more bulge-dominated at 4.4 {mu}m (rest-frame near-infrared). Our analysis reveals that in massive star-forming galaxies at z$sim$2, the radial surface brightness profiles steepen significantly, from a slope of $sim$0.3/dex at 1.5 {mu}m to $sim$1.4/dex at 4.4 {mu}m within radii $<$ 1 kpc. Additionally, we find their total flux contained within the central 1 kpc is approximately 7 times higher in F444W than in F150W. In rest-optical emission, a galaxy's central surface density appears to be the strongest indicator of whether it is quenched or star-forming. Our most significant finding is that at redder wavelengths, the central surface density ratio between quiescent and star-forming galaxies dramatically decreases from $sim$10 to $sim$1. This suggests the high central densities associated with galaxy quenching are already in place during the star-forming phase, imposing new constraints on the transition from star formation to quiescence.
{"title":"JWST Reveals Bulge-Dominated Star-forming Galaxies at Cosmic Noon","authors":"Chloë E. Benton, Erica J. Nelson, Tim B. Miller, Rachel Bezanson, Justus Gibson, Abigail I Hartley, Marco Martorano, Sedona H. Price, Katherine A. Suess, Arjen van der Wel, Pieter van Dokkum, John R. Weaver, Katherine E. Whitaker","doi":"arxiv-2409.08328","DOIUrl":"https://doi.org/arxiv-2409.08328","url":null,"abstract":"Hubble Space Telescope imaging shows that most star-forming galaxies at\u0000cosmic noon -- the peak of cosmic star formation history -- appear\u0000disk-dominated, leaving the origin of the dense cores in their quiescent\u0000descendants unclear. With the James Webb Space Telescope's (JWST)\u0000high-resolution imaging to 5 {mu}m, we can now map the rest-frame\u0000near-infrared emission, a much closer proxy for stellar mass distribution, in\u0000these massive galaxies. We selected 70 star-forming galaxies with\u000010$<$log(M)$<$12 and 1.5$<$z$<$3 in the CEERS survey and compare their\u0000morphologies in the rest-frame optical to those in the rest-frame near-IR.\u0000While the bulk of these galaxies are disk-dominated in 1.5 {mu}m (rest-frame\u0000optical) imaging, they appear more bulge-dominated at 4.4 {mu}m (rest-frame\u0000near-infrared). Our analysis reveals that in massive star-forming galaxies at\u0000z$sim$2, the radial surface brightness profiles steepen significantly, from a\u0000slope of $sim$0.3/dex at 1.5 {mu}m to $sim$1.4/dex at 4.4 {mu}m within\u0000radii $<$ 1 kpc. Additionally, we find their total flux contained within the\u0000central 1 kpc is approximately 7 times higher in F444W than in F150W. In\u0000rest-optical emission, a galaxy's central surface density appears to be the\u0000strongest indicator of whether it is quenched or star-forming. Our most\u0000significant finding is that at redder wavelengths, the central surface density\u0000ratio between quiescent and star-forming galaxies dramatically decreases from\u0000$sim$10 to $sim$1. This suggests the high central densities associated with\u0000galaxy quenching are already in place during the star-forming phase, imposing\u0000new constraints on the transition from star formation to quiescence.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"98 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267391","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}
Ke WangKavli PKU, Yueluo WangKavli PKU, Fengwei XuKavli PKU
The initial conditions are critical for understanding high-mass star formation, but are not well observed. Built on our previous characterization of a Galaxy-wide sample of 463 candidate high-mass starless clumps (HMSCs), here we investigate the dynamical state of a representative subsample of 44 HMSCs (radii 0.13-1.12 pc) using GBT NH3 (1,1) and (2,2) data from the Radio Ammonia Mid-Plane Survey (RAMPS) pilot data release. By fitting the two NH3 lines simultaneously, we obtain velocity dispersion, gas kinetic temperature, NH3 column density and abundance, Mach number, and virial parameter. Thermodynamic analysis reveals that most HMSCs have Mach number $<$5, inconsistent to what have been considered in theoretical models. All but one (43/44) of the HMSCs are gravitationally bound with virial parameter $alpha_{mathrm{vir}} < 2$. Either these massive clumps are in collapsing or magnetic field strengths of 0.10-2.65 mG (average 0.51 mG) would be needed to support them against collapsing. The estimated B-field strength correlates tightly with density, $B_{rm est}/{rm mG}=0.269,(n_{rm H_2}/10^4,{rm cm^{-3}})^{0.61}$, with a similar power-law index as found in observations, but a factor of 4.6 higher in strength. For the first time, the initial dynamical state of high-mass formation regions has been statistically constrained to be sub-virial, in contradictory to theoretical models in virial equilibrium, and in agreement with the lack of observed massive starless cores. The findings urge future observations to quantify the magnetic field support in the prestellar stage of massive clumps, which are rarely explored so far, towards a full understanding of the physical conditions that initiate massive star formation.
{"title":"Massive Star Formation Starts in Sub-virial Dense Clumps Unless Resisted by Strong Magnetic Fields","authors":"Ke WangKavli PKU, Yueluo WangKavli PKU, Fengwei XuKavli PKU","doi":"arxiv-2409.08035","DOIUrl":"https://doi.org/arxiv-2409.08035","url":null,"abstract":"The initial conditions are critical for understanding high-mass star\u0000formation, but are not well observed. Built on our previous characterization of\u0000a Galaxy-wide sample of 463 candidate high-mass starless clumps (HMSCs), here\u0000we investigate the dynamical state of a representative subsample of 44 HMSCs\u0000(radii 0.13-1.12 pc) using GBT NH3 (1,1) and (2,2) data from the Radio Ammonia\u0000Mid-Plane Survey (RAMPS) pilot data release. By fitting the two NH3 lines\u0000simultaneously, we obtain velocity dispersion, gas kinetic temperature, NH3\u0000column density and abundance, Mach number, and virial parameter. Thermodynamic\u0000analysis reveals that most HMSCs have Mach number $<$5, inconsistent to what\u0000have been considered in theoretical models. All but one (43/44) of the HMSCs\u0000are gravitationally bound with virial parameter $alpha_{mathrm{vir}} < 2$.\u0000Either these massive clumps are in collapsing or magnetic field strengths of\u00000.10-2.65 mG (average 0.51 mG) would be needed to support them against\u0000collapsing. The estimated B-field strength correlates tightly with density,\u0000$B_{rm est}/{rm mG}=0.269,(n_{rm H_2}/10^4,{rm cm^{-3}})^{0.61}$, with a\u0000similar power-law index as found in observations, but a factor of 4.6 higher in\u0000strength. For the first time, the initial dynamical state of high-mass\u0000formation regions has been statistically constrained to be sub-virial, in\u0000contradictory to theoretical models in virial equilibrium, and in agreement\u0000with the lack of observed massive starless cores. The findings urge future\u0000observations to quantify the magnetic field support in the prestellar stage of\u0000massive clumps, which are rarely explored so far, towards a full understanding\u0000of the physical conditions that initiate massive star formation.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"168 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195359","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}
Stellar mass and specific angular momentum are two properties of a galaxy that are directly related to its formation history, and hence morphology. In this work, the tight planar relationship between stellar specific angular momentum (j*), mass (M*) and mean effective surface brightness (mu_eff) that was recently constrained using ALFALFA galaxies is measured more accurately using galaxies from the Simba cosmological simulation. The distribution of 179 Simba galaxies in log(j*)-log(M*)-mu_eff space is shown to be very tightly planar with j* proportional to M*^0.694 and the distribution of perpendicular distances between the galaxies and the plane being approximately Gaussian with rms=0.057 dex. The parameterised distribution is used with existing j* and mu_eff measurements of 3607 ALFALFA galaxies and 84 SPARC galaxies to reliably predict their published stellar masses to within ~0.1 to 0.2 dex over several decades of stellar mass. Thus, this work presents a new method of easily generating accurate galaxy stellar mass estimates for late-type galaxies and provides a new measurement of the fundamental link between galaxy morphology, mass and angular momentum.
{"title":"Using the Simba cosmological simulations to measure the planar relation between stellar specific angular momentum, mass and effective surface brightness","authors":"E. Elson","doi":"arxiv-2409.08076","DOIUrl":"https://doi.org/arxiv-2409.08076","url":null,"abstract":"Stellar mass and specific angular momentum are two properties of a galaxy\u0000that are directly related to its formation history, and hence morphology. In\u0000this work, the tight planar relationship between stellar specific angular\u0000momentum (j*), mass (M*) and mean effective surface brightness (mu_eff) that\u0000was recently constrained using ALFALFA galaxies is measured more accurately\u0000using galaxies from the Simba cosmological simulation. The distribution of 179\u0000Simba galaxies in log(j*)-log(M*)-mu_eff space is shown to be very tightly\u0000planar with j* proportional to M*^0.694 and the distribution of perpendicular\u0000distances between the galaxies and the plane being approximately Gaussian with\u0000rms=0.057 dex. The parameterised distribution is used with existing j* and\u0000mu_eff measurements of 3607 ALFALFA galaxies and 84 SPARC galaxies to reliably\u0000predict their published stellar masses to within ~0.1 to 0.2 dex over several\u0000decades of stellar mass. Thus, this work presents a new method of easily\u0000generating accurate galaxy stellar mass estimates for late-type galaxies and\u0000provides a new measurement of the fundamental link between galaxy morphology,\u0000mass and angular momentum.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195357","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}
C. R. Morgan, M. L. Balogh, A. Boselli, M. Fossati, C. Lawlor-Forsyth, E. Sazonova, P. Amram, M. Boquien, J. Braine, L. Cortese, P. Côté, J. C. Cuillandre, L. Ferrarese, S. Gwyn, G. Hensler, Junais, J. Roediger
We examine the prevalence of truncated star-forming disks in the Virgo cluster down to $M_* simeq 10^7 ~text{M}_{odot}$. This work makes use of deep, high-resolution imaging in the H$alpha$+[NII] narrow-band from the Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) and optical imaging from the Next Generation Virgo Survey (NGVS). To aid in understanding the effects of the cluster environment on star formation in Virgo galaxies, we take a physically-motivated approach to define the edge of the star-forming disk via a drop-off in the radial specific star formation rate profile. Comparing with the expected sizes of normal galactic disks provides a measure of how truncated star-forming disks are in the cluster. We find that truncated star-forming disks are nearly ubiquitous across all regions of the Virgo cluster, including beyond the virial radius (0.974 Mpc). The majority of truncated disks at large clustercentric radii are of galaxies likely on first infall. As the intra-cluster medium density is low in this region, it is difficult to explain this population with solely ram-pressure stripping. A plausible explanation is that these galaxies are undergoing starvation of their gas supply before ram-pressure stripping becomes the dominant quenching mechanism. A simple model of starvation shows that this mechanism can produce moderate disk truncations within 1-2 Gyr. This model is consistent with `slow-then-rapid' or `delayed-then-rapid' quenching, where the early starvation mode drives disk truncations without significant change to the integrated star formation rate, and the later ram-pressure stripping mode rapidly quenches the galaxy. The origin of starvation may be in the group structures that exist around the main Virgo cluster, which indicates the importance of understanding pre-processing of galaxies beyond the cluster virial radius.
{"title":"A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE): XVI. The ubiquity of truncated star-forming disks across the Virgo cluster environment","authors":"C. R. Morgan, M. L. Balogh, A. Boselli, M. Fossati, C. Lawlor-Forsyth, E. Sazonova, P. Amram, M. Boquien, J. Braine, L. Cortese, P. Côté, J. C. Cuillandre, L. Ferrarese, S. Gwyn, G. Hensler, Junais, J. Roediger","doi":"arxiv-2409.08339","DOIUrl":"https://doi.org/arxiv-2409.08339","url":null,"abstract":"We examine the prevalence of truncated star-forming disks in the Virgo\u0000cluster down to $M_* simeq 10^7 ~text{M}_{odot}$. This work makes use of\u0000deep, high-resolution imaging in the H$alpha$+[NII] narrow-band from the Virgo\u0000Environmental Survey Tracing Ionised Gas Emission (VESTIGE) and optical imaging\u0000from the Next Generation Virgo Survey (NGVS). To aid in understanding the\u0000effects of the cluster environment on star formation in Virgo galaxies, we take\u0000a physically-motivated approach to define the edge of the star-forming disk via\u0000a drop-off in the radial specific star formation rate profile. Comparing with\u0000the expected sizes of normal galactic disks provides a measure of how truncated\u0000star-forming disks are in the cluster. We find that truncated star-forming\u0000disks are nearly ubiquitous across all regions of the Virgo cluster, including\u0000beyond the virial radius (0.974 Mpc). The majority of truncated disks at large\u0000clustercentric radii are of galaxies likely on first infall. As the\u0000intra-cluster medium density is low in this region, it is difficult to explain\u0000this population with solely ram-pressure stripping. A plausible explanation is\u0000that these galaxies are undergoing starvation of their gas supply before\u0000ram-pressure stripping becomes the dominant quenching mechanism. A simple model\u0000of starvation shows that this mechanism can produce moderate disk truncations\u0000within 1-2 Gyr. This model is consistent with `slow-then-rapid' or\u0000`delayed-then-rapid' quenching, where the early starvation mode drives disk\u0000truncations without significant change to the integrated star formation rate,\u0000and the later ram-pressure stripping mode rapidly quenches the galaxy. The\u0000origin of starvation may be in the group structures that exist around the main\u0000Virgo cluster, which indicates the importance of understanding pre-processing\u0000of galaxies beyond the cluster virial radius.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267388","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}
João P. V. Benedetti, Rogério Riffel, Tiago Ricci, Rogemar A. Riffel, Miriani Pastoriza, Marina Trevisan, Luis G. Dahmer-Hahn, Daniel Ruschel-Dutra, Alberto Rodríguez-Ardila, Anna Ferré-Mateu, Alexandre Vazdekis, João Steiner
We studied the ionized gas in the inner region ($sim680times470$ pc$^2$) of the galaxy NGC 6868 using Gemini/GMOS integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow ($sigmasim110$ km s$^{-1}$) tracing an ionized gas disc and a broad component ($sigmasim300$ km s$^{-1}$) mainly associated with inflowing/outflowing gas. The derived V-band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from $sim 14000$ K in the central region to $gtrsim20000$ K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching $N_esim4000$ cm$^{-3}$ for the broad component decreasing to $N_esim100$ cm$^{-3}$ towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both AGN and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionisation mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy.
我们利用双子座/GMOS 积分场单元观测对 NGC 6868 星系内部区域（$sim680times470$ pc$^2$）的电离气体进行了研究。通道图显示了复杂的运动学和形态学，表明在NGC 6868中有多个过程在起作用。通过发射线拟合，我们在数据中发现了两个无处不在的成分：一个窄成分（$sigmasim110$ km s$^{-1}$）追踪负离子化气体盘，另一个宽成分（$sigmasim300$ km s$^{-1}$）主要与流入/流出气体有关。得出的V波段红度的空间分布与恒星种群合成得出的红度一致，但数值普遍较高。我们首次测量了NGC 6868的电子温度，发现其数值从中心区域的$sim 14000$ K到$gtrsim 20000$ K，温度梯度向外递增。电子密度图显示出一种反比关系，中心值达到 $N_esim4000$ cm$^{-3}$，宽分量值则下降到视场边缘的 $N_esim100$ cm$^{-3}$。利用 BPT 图，我们发现所有的 Spaxels 都与 AGN 和冲击电离一致。然而，当把这些信息与我们的运动学和温度研究结果结合起来，并得到 WHAN 图的进一步支持时，我们认为在 NGC 6868 的中心区域，AGN 是主要的电离机制，而扩展的外围部分则是由热的低质量演化恒星和冲击波共同电离的。根据我们的发现，冲击在这个星系的电离平衡中起着重要作用。
{"title":"Digging deeper into NGC 6868 II: ionized gas and excitation mechanism","authors":"João P. V. Benedetti, Rogério Riffel, Tiago Ricci, Rogemar A. Riffel, Miriani Pastoriza, Marina Trevisan, Luis G. Dahmer-Hahn, Daniel Ruschel-Dutra, Alberto Rodríguez-Ardila, Anna Ferré-Mateu, Alexandre Vazdekis, João Steiner","doi":"arxiv-2409.08047","DOIUrl":"https://doi.org/arxiv-2409.08047","url":null,"abstract":"We studied the ionized gas in the inner region ($sim680times470$ pc$^2$) of\u0000the galaxy NGC 6868 using Gemini/GMOS integral field unit observations. Channel\u0000maps reveal complex kinematics and morphology, indicating multiple processes at\u0000work in NGC 6868. Through emission-line fitting, we identified two ubiquitous\u0000components in our data: a narrow ($sigmasim110$ km s$^{-1}$) tracing an\u0000ionized gas disc and a broad component ($sigmasim300$ km s$^{-1}$) mainly\u0000associated with inflowing/outflowing gas. The derived V-band reddening shows a\u0000spatial distribution consistent with that obtained from stellar population\u0000synthesis, although with generally higher values. For the first time, we\u0000measured the electron temperature in NGC 6868, finding values ranging from\u0000$sim 14000$ K in the central region to $gtrsim20000$ K with an outward\u0000increasing temperature gradient. The electron density map exhibits an inverse\u0000relationship, with central values reaching $N_esim4000$ cm$^{-3}$ for the\u0000broad component decreasing to $N_esim100$ cm$^{-3}$ towards the edges of the\u0000field of view. Using BPT diagrams, we found that all spaxels are consistent\u0000with both AGN and shock ionization. However, when this information is combined\u0000with our kinematic and temperature findings, and further supported by the WHAN\u0000diagram, we argue that an AGN is the dominant ionisation mechanism in the\u0000central region of NGC 6868, while the extended outer component is ionized by a\u0000combination of hot low-mass evolved stars and shocks. According to our\u0000findings, shocks play a significant role in the ionization balance of this\u0000galaxy.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195358","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}
Computational chemistry plays a relevant role in many astrochemical research fields, either by complementing experimental measurements or by deriving parameters difficult to be reproduced by laboratories. While the role of computational spectroscopy in assisting new observations in space is described, the core of the chapter is the investigation of the collisional radiative transfer and the bimolecular reactive processes occurring in the gas-phase conditions of the interstellar medium, using as a guide the contributions presented by the authors at the "Second Italian National Congress on Proto(-planetary) Astrochemistry", held in Trieste in September 2023. In particular, the need for accurate datasets of collisional coefficients to model molecular abundances will be discussed. Then, the role of quantum chemistry in the investigation of interstellar-relevant potential energy surfaces will be described, focusing on accurate thermodynamic quantities for the estimate of rate coefficients.
{"title":"Ab initio Calculations for Astrochemistry","authors":"Francesca Tonolo, Silvia Alessandrini","doi":"arxiv-2409.07211","DOIUrl":"https://doi.org/arxiv-2409.07211","url":null,"abstract":"Computational chemistry plays a relevant role in many astrochemical research\u0000fields, either by complementing experimental measurements or by deriving\u0000parameters difficult to be reproduced by laboratories. While the role of\u0000computational spectroscopy in assisting new observations in space is described,\u0000the core of the chapter is the investigation of the collisional radiative\u0000transfer and the bimolecular reactive processes occurring in the gas-phase\u0000conditions of the interstellar medium, using as a guide the contributions\u0000presented by the authors at the \"Second Italian National Congress on\u0000Proto(-planetary) Astrochemistry\", held in Trieste in September 2023. In\u0000particular, the need for accurate datasets of collisional coefficients to model\u0000molecular abundances will be discussed. Then, the role of quantum chemistry in\u0000the investigation of interstellar-relevant potential energy surfaces will be\u0000described, focusing on accurate thermodynamic quantities for the estimate of\u0000rate coefficients.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195406","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}
Gan Luo, Thomas G. Bisbas, Marco Padovani, Brandt A. L. Gaches
The cosmic-ray ionization rate ($zeta_2$) is one of the key parameters in star formation, since it regulates the chemical and dynamical evolution of molecular clouds by ionizing molecules and determining the coupling between the magnetic field and gas. However, measurements of $zeta_2$ in dense clouds (e.g., $n_{rm H} geq 10^4$ cm$^{-3}$) are difficult and sensitive to the model assumptions. The aim is to find a convenient analytic approach that can be used in high-mass star-forming regions (HMSFRs), especially for warm gas environments such as hot molecular cores (HMCs). We propose a new analytic approach to calculate $zeta_2$ through HCO$^+$, N$_2$H$^+$, and CO measurements. Our method gives a good approximation, to within $50$%, of $zeta_2$ in dense and warm gas (e.g., $n_{rm H} geq 10^4$ cm$^{-3}$, $T = 50, 100$ K) for $A_{rm V} geq 4$ mag and $t geq 2times10^4$ yr at Solar metallicity. The analytic approach gives better results for higher densities. However, it starts to underestimate the CRIR at low metallicity ($Z = 0.1Z_odot$) and high CRIR ($zeta_2 geq 3times10^{-15}$ s$^{-1}$). By applying our method to the OMC-2 FIR4 envelope and the L1157-B1 shock region, we find $zeta_2$ values of $(1.0pm0.3)times10^{-14}$ s$^{-1}$ and $(2.2pm0.4)times10^{-16}$ s$^{-1}$, consistent with those previously reported. We calculate $zeta_2$ toward a total of 82 samples in HMSFRs, finding that the average value of $zeta_2$ toward all HMC samples ($zeta_2$ = (7.4$pm$5.0)$times$10$^{-16}$ s$^{-1}$) is more than an order of magnitude higher than the theoretical prediction of cosmic-ray attenuation models, favoring the scenario that locally accelerated cosmic rays in embedded protostars should be responsible for the observed high $zeta_2$.
{"title":"A new analytic approach to infer the cosmic-ray ionization rate in hot molecular cores from HCO$^+$, N$_2$H$^+$, and CO observations","authors":"Gan Luo, Thomas G. Bisbas, Marco Padovani, Brandt A. L. Gaches","doi":"arxiv-2409.07181","DOIUrl":"https://doi.org/arxiv-2409.07181","url":null,"abstract":"The cosmic-ray ionization rate ($zeta_2$) is one of the key parameters in\u0000star formation, since it regulates the chemical and dynamical evolution of\u0000molecular clouds by ionizing molecules and determining the coupling between the\u0000magnetic field and gas. However, measurements of $zeta_2$ in dense clouds\u0000(e.g., $n_{rm H} geq 10^4$ cm$^{-3}$) are difficult and sensitive to the\u0000model assumptions. The aim is to find a convenient analytic approach that can\u0000be used in high-mass star-forming regions (HMSFRs), especially for warm gas\u0000environments such as hot molecular cores (HMCs). We propose a new analytic\u0000approach to calculate $zeta_2$ through HCO$^+$, N$_2$H$^+$, and CO\u0000measurements. Our method gives a good approximation, to within $50$%, of\u0000$zeta_2$ in dense and warm gas (e.g., $n_{rm H} geq 10^4$ cm$^{-3}$, $T =\u000050, 100$ K) for $A_{rm V} geq 4$ mag and $t geq 2times10^4$ yr at Solar\u0000metallicity. The analytic approach gives better results for higher densities.\u0000However, it starts to underestimate the CRIR at low metallicity ($Z =\u00000.1Z_odot$) and high CRIR ($zeta_2 geq 3times10^{-15}$ s$^{-1}$). By\u0000applying our method to the OMC-2 FIR4 envelope and the L1157-B1 shock region,\u0000we find $zeta_2$ values of $(1.0pm0.3)times10^{-14}$ s$^{-1}$ and\u0000$(2.2pm0.4)times10^{-16}$ s$^{-1}$, consistent with those previously\u0000reported. We calculate $zeta_2$ toward a total of 82 samples in HMSFRs,\u0000finding that the average value of $zeta_2$ toward all HMC samples ($zeta_2$ =\u0000(7.4$pm$5.0)$times$10$^{-16}$ s$^{-1}$) is more than an order of magnitude\u0000higher than the theoretical prediction of cosmic-ray attenuation models,\u0000favoring the scenario that locally accelerated cosmic rays in embedded\u0000protostars should be responsible for the observed high $zeta_2$.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195376","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 introduce genesis-metallicity, a gas-phase metallicity measurement python software employing the direct and strong-line methods depending on the available oxygen lines. The non-parametric strong-line estimator is calibrated based on a kernel density estimate in the 4-dimensional space of O2 = [O II]$lambdalambda 3727,29$/H$beta$; O3 = [O III]$lambda 5007$/H$beta$; H$beta$ equivalent width EW(H$beta$); and gas-phase metallicity $12 + log$(O/H). We use a calibration sample of 1551 galaxies at $0 < z < 10$, with direct-method metallicity measurements compiled from the JWST/NIRSpec and ground-based observations. In particular, we report 145 new NIRSpec direct-method metallicity measurements at $z > 1$. We show that the O2, O3, and EW(H$beta$) measurements are sufficient for a gas-phase metallicity estimate that is more accurate than 0.09 dex. Our calibration is universal, meaning that its accuracy does not depend on the target redshift. Furthermore, the direct-method module employs a non-parametric $t_e$(O II) electron temperature estimator based on a kernel density estimate in the 5-dimensional space of O2, O3, EW(H$beta$), $t_e$(O II), and $t_e$(O III). This $t_e$(O II) estimator is calibrated based on 1001 spectra with [O III]$lambda 4363$ and [O II]$lambdalambda 7320,30$ detections, notably reporting 30 new NIRSpec detections of the [O II]$lambdalambda 7320,30$ doublet. We make genesis-metallicity and its calibration data publicly available and commit to keeping both up-to-date in light of the incoming data.
{"title":"Genesis-Metallicity: Universal Non-Parametric Gas-Phase Metallicity Estimation","authors":"Danial Langeroodi, Jens Hjorth","doi":"arxiv-2409.07455","DOIUrl":"https://doi.org/arxiv-2409.07455","url":null,"abstract":"We introduce genesis-metallicity, a gas-phase metallicity measurement python\u0000software employing the direct and strong-line methods depending on the\u0000available oxygen lines. The non-parametric strong-line estimator is calibrated\u0000based on a kernel density estimate in the 4-dimensional space of O2 = [O\u0000II]$lambdalambda 3727,29$/H$beta$; O3 = [O III]$lambda 5007$/H$beta$;\u0000H$beta$ equivalent width EW(H$beta$); and gas-phase metallicity $12 +\u0000log$(O/H). We use a calibration sample of 1551 galaxies at $0 < z < 10$, with\u0000direct-method metallicity measurements compiled from the JWST/NIRSpec and\u0000ground-based observations. In particular, we report 145 new NIRSpec\u0000direct-method metallicity measurements at $z > 1$. We show that the O2, O3, and\u0000EW(H$beta$) measurements are sufficient for a gas-phase metallicity estimate\u0000that is more accurate than 0.09 dex. Our calibration is universal, meaning that\u0000its accuracy does not depend on the target redshift. Furthermore, the\u0000direct-method module employs a non-parametric $t_e$(O II) electron temperature\u0000estimator based on a kernel density estimate in the 5-dimensional space of O2,\u0000O3, EW(H$beta$), $t_e$(O II), and $t_e$(O III). This $t_e$(O II) estimator is\u0000calibrated based on 1001 spectra with [O III]$lambda 4363$ and [O\u0000II]$lambdalambda 7320,30$ detections, notably reporting 30 new NIRSpec\u0000detections of the [O II]$lambdalambda 7320,30$ doublet. We make\u0000genesis-metallicity and its calibration data publicly available and commit to\u0000keeping both up-to-date in light of the incoming data.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"168 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195369","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}
Francesca Pinna, Robert J. J. Grand, Marie Martig, Francesca Fragkoudi
We assessed the ability to recover chemical bimodalities in integral-field spectroscopy (IFS) observations of edge-on galaxies, using 24 Milky Way-mass galaxies from the AURIGA zoom-in cosmological simulations. We first analyzed the distribution of single stellar particles in the [Mg/Fe] - [Fe/H] plane. Then we produced mock IFS [Mg/Fe] and [Fe/H] maps of galaxies seen edge on, and considered integrated stellar-population properties (projected and spatially binned). We investigated how the distribution of stars in the [Mg/Fe] - [Fe/H] plane is affected by edge-on projection and spatial binning. Bimodality is preserved while distributions change their shapes. Naturally, broad distributions of individual star particles are narrowed into smaller [Mg/Fe] and [Fe/H] ranges for spatial bins. We observe continuous distributions, bimodal in most cases. The overlap in [Fe/H] is small, and different [Mg/Fe] components show up as peaks instead of sequences (even when the latter are present for individual particles). The larger the spatial bins, the narrower the [Mg/Fe] - [Fe/H] distribution. This narrowing helps amplify the density of different [Mg/Fe] peaks, often leading to a clearer bimodality in mock IFS observations than for original star particles. We have also assessed the correspondence of chemical bimodalities with the distinction between geometric thick and thin disks. Their individual particles have different distributions but mostly overlap in [Mg/Fe] and [Fe/H]. However, integrated properties of geometric thick and thin disks in mock maps do mostly segregate into different regions of the [Mg/Fe] - [Fe/H] plane. In bimodal distributions, they correspond to the two distinct peaks. Our results show that this approach can be used for bimodality studies in future IFS observations of edge-on external galaxies.
{"title":"Recovering chemical bimodalities in observed edge-on stellar disks: insights from AURIGA simulations","authors":"Francesca Pinna, Robert J. J. Grand, Marie Martig, Francesca Fragkoudi","doi":"arxiv-2409.07533","DOIUrl":"https://doi.org/arxiv-2409.07533","url":null,"abstract":"We assessed the ability to recover chemical bimodalities in integral-field\u0000spectroscopy (IFS) observations of edge-on galaxies, using 24 Milky Way-mass\u0000galaxies from the AURIGA zoom-in cosmological simulations. We first analyzed\u0000the distribution of single stellar particles in the [Mg/Fe] - [Fe/H] plane.\u0000Then we produced mock IFS [Mg/Fe] and [Fe/H] maps of galaxies seen edge on, and\u0000considered integrated stellar-population properties (projected and spatially\u0000binned). We investigated how the distribution of stars in the [Mg/Fe] - [Fe/H]\u0000plane is affected by edge-on projection and spatial binning. Bimodality is\u0000preserved while distributions change their shapes. Naturally, broad\u0000distributions of individual star particles are narrowed into smaller [Mg/Fe]\u0000and [Fe/H] ranges for spatial bins. We observe continuous distributions,\u0000bimodal in most cases. The overlap in [Fe/H] is small, and different [Mg/Fe]\u0000components show up as peaks instead of sequences (even when the latter are\u0000present for individual particles). The larger the spatial bins, the narrower\u0000the [Mg/Fe] - [Fe/H] distribution. This narrowing helps amplify the density of\u0000different [Mg/Fe] peaks, often leading to a clearer bimodality in mock IFS\u0000observations than for original star particles. We have also assessed the\u0000correspondence of chemical bimodalities with the distinction between geometric\u0000thick and thin disks. Their individual particles have different distributions\u0000but mostly overlap in [Mg/Fe] and [Fe/H]. However, integrated properties of\u0000geometric thick and thin disks in mock maps do mostly segregate into different\u0000regions of the [Mg/Fe] - [Fe/H] plane. In bimodal distributions, they\u0000correspond to the two distinct peaks. Our results show that this approach can\u0000be used for bimodality studies in future IFS observations of edge-on external\u0000galaxies.","PeriodicalId":501187,"journal":{"name":"arXiv - PHYS - Astrophysics of Galaxies","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195379","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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