arXiv subjects

Alberto Bolatto

Publications and source records attributed to Alberto Bolatto.

At least 37 records · Page 2Linked to original sources

arXiv2024

The JWST Resolved Stellar Populations Early Release Science Program V. DOLPHOT Stellar Photometry for NIRCam and NIRISS

We present NIRCam and NIRISS modules for DOLPHOT, a widely-used crowded field stellar photometry package. We describe details of the modules including pixel masking, astrometric alignment, star finding, photometry, catalog creation, and artificial star tests (ASTs). We tested these modules using NIRCam and NIRISS images of M92 (a Milky Way globular cluster), Draco II (an ultra-faint dwarf galaxy), and WLM (a star-forming dwarf galaxy). DOLPHOT's photometry is highly precise and the color-magnitude diagrams are deeper and have better definition than anticipated during original program design in 2017. The primary systematic uncertainties in DOLPHOT's photometry arise from mismatches in the model and observed point spread functions (PSFs) and aperture corrections, each contributing $\lesssim0.01$ mag to the photometric error budget. Version 1.2 of WebbPSF models, which include charge diffusion and interpixel capacitance effects, significantly reduced PSF-related uncertainties. We also observed minor ($\lesssim0.05$ mag) chip-to-chip variations in NIRCam's zero points, which will be addressed by the JWST flux calibration program. Globular cluster observations are crucial for photometric calibration. Temporal variations in the photometry are generally $\lesssim0.01$ mag, although rare large misalignment events can introduce errors up to 0.08 mag. We provide recommended DOLPHOT parameters, guidelines for photometric reduction, and advice for improved observing strategies. Our ERS DOLPHOT data products are available on MAST, complemented by comprehensive online documentation and tutorials for using DOLPHOT with JWST imaging data.

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arXiv2023

The JWST Resolved Stellar Populations Early Release Science Program IV: The Star Formation History of the Local Group Galaxy WLM

We present the first star formation history (SFH) and age-metallicity relation (AMR) derived from resolved stellar populations imaged with the JWST NIRCam instrument. The target is the Local Group star-forming galaxy WLM at 970 kpc. The depth of the color-magnitude diagram (CMD) reaches below the oldest main sequence turn-off with a SNR=10 at M_F090W=+4.6 mag; this is the deepest CMD for any galaxy that is not a satellite of the Milky Way. We use Hubble Space Telescope (HST) optical imaging that overlaps with the NIRCam observations to directly evaluate the SFHs derived based on data from the two great observatories. The JWST and HST-based SFHs are in excellent agreement. We use the metallicity distribution function measured from stellar spectra to confirm the trends in the AMRs based on the JWST data. Together, these results confirm the efficacy of recovering a SFH and AMR with the NIRCam F090W-F150W filter combination and provide validation of the sensitivity and accuracy of stellar evolution libraries in the near-infrared relative to the optical for SFH recovery work. From the JWST data, WLM shows an early onset to star formation, followed by an extended pause post-reionization before star formation re-ignites, which is qualitatively similar to what has been observed in the isolated galaxies Leo~A and Aquarius. Quantitatively, 15% of the stellar mass formed in the first Gyr, while only 10% formed over the next ~5 Gyr; the stellar mass then rapidly doubled in ~2.5 Gyr, followed by constant star formation over the last ~5 Gyr.

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arXiv2023

GBT/Argus Observations of Molecular Gas in the Inner Regions of IC 342

We report observations of the ground state transitions of $^{12}$CO, $^{13}$CO C$^{18}$O, HCN, and HCO$^+$ at 88-115 GHz in the inner region of the nearby galaxy IC 342. These data were obtained with the 16-pixel spectroscopic focal plane array Argus on the 100-m Robert C. Byrd Green Bank Telescope (GBT) at 6-9$^{\prime\prime}$ resolution. In the nuclear bar region, the intensity distributions of $^{12}$CO(1-0) and $^{13}$CO(1-0) emission trace moderate densities, and differ from the dense gas distributions sampled in C$^{18}$O(1-0), HCN(1-0), and HCO$^+$(1-0). We observe a constant HCN(1-0)-to-HCO$^+$(1-0) ratio of 1.2$\pm$0.1 across the whole $\sim$1 kpc bar. This indicates that HCN(1-0) and HCO$^+$(1-0) lines have intermediate optical depth, and that the corresponding $n_{\textrm{H}_2}$ of the gas producing the emission is of 10$^{4.5-6}$ cm$^{-3}$. We show that HCO$^+$(1-0) is thermalized and HCN(1-0) is close to thermalization. The very tight correlation between HCN(1-0) and HCO$^+$(1-0) intensities across the 1~kpc bar suggests that this ratio is more sensitive to the relative abundance of the two species than to the gas density. We confirm the angular offset ($\sim$10$^{\prime\prime}$) between the spatial distribution of molecular gas and the star formation sites. Finally, we find a breakdown of the $L_\textrm{IR}$-$L_\textrm{HCN}$ correlation at high spatial resolution due to the effect of incomplete sampling of star-forming regions by HCN emission in IC 342. The scatter of the $L_\textrm{IR}$-$L_\textrm{HCN}$ relation decreases as the spatial scale increases from 10$^{\prime\prime}$~to 30$^{\prime\prime}$ (170-510~pc), and is comparable to the scatter of the global relation at the scale of 340 pc.

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arXiv2023

The JWST Resolved Stellar Populations Early Release Science Program II. Survey Overview

We present the JWST Resolved Stellar Populations Early Release Science (ERS) science program. We obtained 27.5 hours of NIRCam and NIRISS imaging of three targets in the Local Group (Milky Way globular cluster M92, ultra-faint dwarf galaxy Draco II, star-forming dwarf galaxy WLM), which span factors of $\sim10^5$ in luminosity, $\sim10^4$ in distance, and $\sim10^5$ in surface brightness. We describe the survey strategy, scientific and technical goals, implementation details, present select NIRCam color-magnitude diagrams (CMDs), and validate the NIRCam exposure time calculator (ETC). Our CMDs are among the deepest in existence for each class of target. They touch the theoretical hydrogen burning limit in M92 ($<0.08$ $M_{\odot}$; SNR $\sim5$ at $m_{F090W}\sim28.2$; $M_{F090W}\sim+13.6$), include the lowest-mass stars observed outside the Milky Way in Draco II (0.09 $M_{\odot}$; SNR $=10$ at $m_{F090W}\sim29$; $M_{F090W}\sim+12.1$), and reach $\sim1.5$ magnitudes below the oldest main sequence turnoff in WLM (SNR $=10$ at $m_{F090W}\sim29.5$; $M_{F090W}\sim+4.6$). The PARSEC stellar models provide a good qualitative match to the NIRCam CMDs, though are $\sim0.05$ mag too blue compared to M92 F090W$-$F150W data. The NIRCam ETC (v2.0) matches the SNRs based on photon noise from DOLPHOT stellar photometry in uncrowded fields, but the ETC may not be accurate in more crowded fields, similar to what is known for HST. We release beta versions of DOLPHOT NIRCam and NIRISS modules to the community. Results from this ERS program will establish JWST as the premier instrument for resolved stellar populations studies for decades to come.

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arXiv2022

Stellar Masses of Clumps in Gas-rich, Turbulent Disk Galaxies

In this paper we use HST/WFC3 observations of 6 galaxies from the DYNAMO survey, combined with stellar population modelling of the SED, to determine the stellar masses of DYNAMO clumps. The DYNAMO sample has been shown to have properties similar to $z\approx1.5$ turbulent, clumpy disks. DYNAMO sample clump masses offer a useful comparison for studies of $z>1$ in that the galaxies have the same properties, yet the observational biases are significantly different. Using DYNAMO we can more easily probe rest-frame near-IR wavelengths and also probe finer spatial scales. We find that the stellar mass of DYNAMO clumps is typically $10^{7}-10^8 \mathrm{M}_\odot$. We employ a technique that makes non-parametric corrections in removal of light from nearby clumps, and carries out a locally determined disk subtraction. The process of disk subtraction is the dominant effect, and can alter clump masses at the 0.3~dex level. Using these masses, we investigate the stellar mass function of clumps in DYNAMO galaxies. DYNAMO stellar mass functions follow a declining power law with slope $α\approx -1.4$, which is slightly shallower than, but similar to what is observed in $z>1$ lensed galaxies. We compare DYNAMO clump masses to results of simulations. The masses and galactocentric position of clumps in DYNAMO galaxies are more similar to long-lived clumps in simulations. Similar to recent DYNAMO results on the stellar population gradients, these results are consistent with simulations that do not employ strong "early" radiative feedback prescriptions.

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arXiv2022

The DUVET Survey: Resolved Maps of Star Formation Driven Outflows in a Compact, Starbursting Disk Galaxy

We study star formation driven outflows in a $z\sim0.02$ starbursting disk galaxy, IRAS08339+6517, using spatially resolved measurements from the Keck Cosmic Web Imager (KCWI). We develop a new method incorporating a multi-step process to determine whether an outflow should be fit in each spaxel, and then subsequently decompose the emission line into multiple components. We detect outflows ranging in velocity, $v_{\rm out}$, from $100-600$ km s$^{-1}$ across a range of star formation rate surface densities, $Σ_{\rm SFR}$, from $\sim$0.01-10 M$_\odot$ yr$^{-1}$ kpc$^{-2}$ in resolution elements of a few hundred parsec. Outflows are detected in $\sim100\%$ of all spaxels within the half-light radius, and $\sim70\%$ within $r_{90}$, suggestive of a high covering fraction for this starbursting disk galaxy. Around $2/3$ of the total outflowing mass originates from the star forming ring, which corresponds to $<10\%$ of the total area of the galaxy. We find that the relationship between $v_{\rm out}$ and the $Σ_{\rm SFR}$, as well as between the mass loading factor, $η$, and the $Σ_{\rm SFR}$, are consistent with trends expected from energy-driven feedback models. We study the resolution effects on this relationship and find stronger correlations above a re-binned size-scale of $\sim500$ pc. Conversely, we do not find statistically significant consistency with the prediction from momentum-driven winds.

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arXiv2021

The DUVET Survey: Direct $T_e$-based metallicity mapping of metal-enriched outflows and metal-poor inflows in Mrk 1486

We present electron temperature ($T_e$) maps for the edge-on system Mrk 1486, affording "direct-method" gas-phase metallicity measurements across $5.\!\!^{\prime\prime}8$ (4.1 kpc) along the minor axis and $9.\!\!^{\prime\prime}9$ (6.9 kpc) along the major axis. These maps, enabled by strong detections of the [OIII]$λ$4363 auroral emission line across a large spatial extent of Mrk 1486, reveal a clear negative minor axis $T_e$ gradient in which temperature decreases with increasing distance from the disk plane. We find that the lowest metallicity spaxels lie near the extremes of the major axis, while the highest metallicity spaxels lie at large spatial offsets along the minor axis. This is consistent with a picture in which low metallicity inflows dilute the metallicity at the edges of the major axis of the disk, while star formation drives metal-enriched outflows along the minor axis. We find that the outflow metallicity in Mrk 1486 is 0.20 dex (1.6 times) higher than the average ISM metallicity, and more than 0.80 dex (6.3 times) higher than metal-poor inflowing gas, which we observe to be below 5 % $Z_\odot$. This is the first example of metallicity measurements made simultaneously for inflowing, outflowing, and inner disk ISM gas using consistent $T_e$-based methodology. These measurements provide unique insight into how baryon cycle processes contribute to the assembly of a galaxy like Mrk 1486.

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arXiv2021

An ACA Survey of [CI] $^3P_1-^3P_0$, CO $J=4-3$, and Dust Continuum in Nearby U/LIRG

We present the results of surveying [CI] $^3P_1-^3P_0$, $^{12}$CO $J=4-3$, and 630 $μ$m dust continuum emission for 36 nearby ultra/luminous infrared galaxies (U/LIRGs) using the Band 8 receiver mounted on the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array. We describe the survey, observations, data reduction, and results; the main results are as follows. (i) We confirmed that [CI] $^3P_1-^3P_0$ has a linear relationship with both the $^{12}$CO $J=4-3$and 630 $μ$m continuum. (ii) In NGC 6052 and NGC 7679, $^{12}$CO $J=4-3$ was detected but [CI] $^3P_1-^3P_0$ was not detected with a [CI] $^3P_1-^3P_0$/ $^{12}$CO $J=4-3$ ratio of $\lesssim0.08$. Two possible scenarios of weak [CI] $^3P_1-^3P_0$ emission are C$^0$-poor/CO-rich environments or an environment with an extremely large [CI] $^3P_1-^3P_0$ missing flux. (iii) There is no clear evidence showing that galaxy mergers, AGNs, and dust temperatures control the ratios of [CI] $^3P_1-^3P_0$/ $^{12}$CO $J=4-3$ and $L'_{\rm [CI](1-0)}/L_{\rm 630μm}$. (iv) We compare our nearby U/LIRGs with high-z galaxies, such as galaxies on the star formation main sequence (MS) at z$\sim1$ and submillimeter galaxies (SMGs) at $z=2-4$. We found that the mean value for the [CII] $^3P_1$--$^3P_0$/ $^{12}$CO $J=4-3$ ratio of U/LIRGs is similar to that of SMGs but smaller than that of galaxies on the MS.

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arXiv2021

The EDGE-CALIFA Survey: Central molecular gas depletion in AGN host galaxies -- a smoking gun for quenching?

Feedback from an active galactic nucleus (AGN) is often implicated as a mechanism that leads to the quenching of galactic star formation. However, AGN-driven quenching is challenging to reconcile with observations that AGN hosts tend to harbour equal (or even excess) amounts of gas compared with inactive galaxies of similar stellar mass. In this paper, we investigate whether AGN feedback happens on sub-galactic (kpc) scales, an effect that might be difficult to detect with global gas measurements. Using kpc-scale measurements of molecular gas (Sigma_H2) and stellar mass (Sigma_*) surface densities taken from the EDGE-CALIFA survey, we show that the gas fractions of central AGN regions are typically a factor of ~2 lower than in star-forming regions. Based on four galaxies with the best spaxel statistics, the difference between AGN and star-forming gas fractions is seen even within a given galaxy, indicating that AGN feedback is able to deplete the molecular gas reservoir in the central few kpc.

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arXiv2021

The Case for Thermalization as a Contributor to the [CII] Deficit

The [CII] deficit, which describes the observed decrease in the ratio of [CII] 158 micron emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [CII] detections from across the observable universe. In an attempt to further decode the cause of the [CII] deficit, the [CII] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [CII] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [CII] line in HII regions plays a significant role in the deficit observed in our sample.

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arXiv2021

Overview and status of EXCLAIM, the experiment for cryogenic large-aperture intensity mapping

The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a balloon-borne far-infrared telescope that will survey star formation history over cosmological time scales to improve our understanding of why the star formation rate declined at redshift z < 2, despite continued clustering of dark matter. Specifically,EXCLAIM will map the emission of redshifted carbon monoxide and singly-ionized carbon lines in windows over a redshift range 0 < z < 3.5, following an innovative approach known as intensity mapping. Intensity mapping measures the statistics of brightness fluctuations of cumulative line emissions instead of detecting individual galaxies, thus enabling a blind, complete census of the emitting gas. To detect this emission unambiguously, EXCLAIM will cross-correlate with a spectroscopic galaxy catalog. The EXCLAIM mission uses a cryogenic design to cool the telescope optics to approximately 1.7 K. The telescope features a 90-cm primary mirror to probe spatial scales on the sky from the linear regime up to shot noise-dominated scales. The telescope optical elements couple to six μ-Spec spectrometer modules, operating over a 420-540 GHz frequency band with a spectral resolution of 512 and featuring microwave kinetic inductance detectors. A Radio Frequency System-on-Chip (RFSoC) reads out the detectors in the baseline design. The cryogenic telescope and the sensitive detectors allow EXCLAIM to reach high sensitivity in spectral windows of low emission in the upper atmosphere. Here, an overview of the mission design and development status since the start of the EXCLAIM project in early 2019 is presented.

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arXiv2020

Discovery of a [CI]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052

We report sensitive [\ion{C}{1}]~$^3P_1$--$^3P_0$ and $^{12}$CO~$J$=4--3 observations of the nearby merging galaxy NGC 6052 using the Morita (Atacama Compact) Array of ALMA. We detect $^{12}$CO~$J$=4--3 toward the northern part of NGC 6052, but [\ion{C}{1}]~$^3P_1$--$^3P_0$ is not detected with a [\ion{C}{1}]~$^3P_1$--$^3P_0$ to $^{12}$CO~$J$=4--3 line luminosity ratio of$~\lesssim0.07$. According to models of photodissociation regions, the unusual weakness of [\ion{C}{1}]~$^3P_1$--$^3P_0$ relative to $^{12}$CO~$J$=4--3 can be explained if the interstellar medium has a hydrogen density larger than $10^5\,{\rm cm}^{-3}$, conditions that might arise naturally in the ongoing merging process in NGC 6052. Its [\ion{C}{1}]~$^3P_1$--$^3P_0$ emission is also weaker than expected given the molecular gas mass inferred from previous measurements of $^{12}$CO~$J$=1--0 and $^{12}$CO~$J$=2--1. This suggests that [\ion{C}{1}]~$^3P_1$--$^3P_0$ may not be a reliable tracer of molecular gas mass in this galaxy. NGC 6052 is a unique laboratory to investigate how the merger process impacts the molecular gas distribution.

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arXiv2020

Star formation traced by optical and millimeter hydrogen recombination lines and free-free emissions in the dusty merging galaxy NGC 3256 -- MUSE/VLT and ALMA synergy

A galaxy-galaxy merger and the subsequent triggering of starburst activity are fundamental processes linked to the morphological transformation of galaxies and the evolution of star formation across the history of the Universe. Both nuclear and disk-wide starbursts are assumed to occur during the merger process. However, quantifying both nuclear and disk-wide star formation activity is non-trivial because the nuclear starburst is dusty in the most active merging starburst galaxies. This paper presents a new approach to this problem: combining hydrogen recombination lines in optical, millimeter, and free-free emission. Using NGC~3256 as a case study, H$β$, H40$α$, and free-free emissions are investigated using the Multi Unit Spectroscopic Explorer at the Very Large Telescope of the European Southern Observatory (MUSE/VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA). The H$β$ image obtained by MUSE identifies star-forming regions outside the nuclear regions, suggesting a disk-wide starburst. In contrast, the H40$α$ image obtained by ALMA identifies a nuclear starburst where optical lines are undetected due to dust extinction ($A_{\rm V}\sim25$). Combining both MUSE and ALMA observations, we conclude that the total SFR is $49\pm2~M_{\odot}$~yr$^{-1}$ and the contributions from nuclear and disk-wide starbursts are $\sim34~\%$ and $\sim66~\%$, respectively. This suggests the dominance of disk-wide star formation in NGC~3256. In addition, pixel-by-pixel analyses for disk-wide star-forming regions suggest that shock gas tracers (e.g., CH$_3$OH) are enhanced where gas depletion time ($τ_{\rm gas}$=$M_{\rm gas}/SFR$) is long. This possibly means that merger-induced shocks regulate disk-wide star formation activities.

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arXiv2019

The Dark Matter Distributions in Low-Mass Disk Galaxies. II. The Inner Density Profiles

Dark matter-only simulations predict that dark matter halos have steep, cuspy inner density profiles, while observations of dwarf galaxies find a range of inner slopes that are often much shallower. There is debate whether this discrepancy can be explained by baryonic feedback or if it may require modified dark matter models. In Paper 1 of this series, we obtained high-resolution integral field H$α$ observations for 26 dwarf galaxies with $M_*=10^{8.1}-10^{9.7}\textrm{M}_\odot$. We derived rotation curves from our observations, which we use here to construct mass models. We model the total mass distribution as the sum of a generalized Navarro-Frenk-White (NFW) dark matter halo and the stellar and gaseous components. Our analysis of the slope of the dark matter density profile focuses on the inner 300-800 pc, chosen based on the resolution of our data and the region resolved by modern hydrodynamical simulations. The inner slope measured using ionized and molecular gas tracers is consistent, and it is additionally robust to the choice of stellar mass-to-light ratio. We find a range of dark matter profiles, including both cored and cuspy slopes, with an average of $ρ_{\rm DM}\sim r^{-0.74\pm 0.07}$, shallower than the NFW profile, but steeper than those typically observed for lower-mass galaxies with $M_*\sim 10^{7.5}\textrm{M}_\odot$. Simulations that reproduce the observed slopes in those lower-mass galaxies also produce slopes that are too shallow for galaxies in our mass range. We therefore conclude that supernova feedback models do not yet provide a fully satisfactory explanation for the observed trend in dark matter slopes.

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arXiv2019

Mapping Spatial Variations of HI Turbulent Properties in the Small and Large Magellanic Cloud

We developed methods for mapping spatial variations of the spatial power spectrum (SPS) and structure function (SF) slopes, with a goal of connecting neutral hydrogen (HI) statistical properties with the turbulent drivers. The new methods were applied on the HI observations of the Small and Large Magellanic Clouds (SMC and LMC). In the case of the SMC, we find highly uniform turbulent properties of HI, with no evidence for local enhancements of turbulence due to stellar feedback. Such properties could be caused by a significant turbulent driving on large-scales. Alternatively, a significant line-of-sight depth of the SMC could be masking out localized regions with a steeper SPS slope caused by stellar feedback. In contrast to the SMC, the LMC HI shows a large diversity in terms of its turbulent properties. Across most of the LMC, the small-scale SPS slope is steeper than the large-scale slope due to the presence of the HI disk. On small spatial scales, we find several areas of localized steepening of the SPS slope around major HII regions, with the 30 Doradus region being the most prominent. This is in agreement with predictions from numerical simulations which suggest steepening of the SPS slope due to stellar feedback eroding and destroying interstellar clouds. We also find localized steepening of the large-scale SPS slope in the outskirts of the LMC. This is likely caused by the flaring of the HI disk, or alternatively ram-pressure stripping of the LMC disk due to the interactions with the surrounding halo gas.

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arXiv2019

A Search for Intrinsic HI 21 cm and OH 18 cm Absorption Toward Compact Radio Sources

We present the results of a large search for intrinsic HI 21 cm and OH 18 cm absorption in 145 compact radio sources in the redshift range 0.02< z <3.8 with the Green Bank Telescope. We re-detect HI 21 cm absorption toward six known absorption systems but detect no new HI or OH absorption in 102 interference-free sources. 79 sources have not previously been observed for HI 21 cm absorption. We recover a mean optical depth limit of $τ_{3σ}<0.023$ for all the non-detections in the survey. Our results do not support the high intrinsic absorption rates found by previous studies in compact radio sources at low redshift. Our results do, however, support the hypothesis proposed by Curran et al. (2008) that high ultraviolet (UV) luminosity active galactic nuclei (AGN) do not show intrinsic HI 21 cm absorption, confirming a threshold of $L_{\rm UV} = 10^{23}$ W Hz$^{-1}$, above which our intrinsic absorption fraction is zero (54 sources). The exact nature of the UV luminosity effect on HI absorption systems remains ambiguous. We additionally find no statistical correlation between the 1.4 GHz radio luminosity or the source size and the 21~cm absorption detection rate. We attribute the lack of intrinsic absorption in our survey to the UV luminosity effect caused by an optical selection bias and a decreased column density sensitivity with increasing redshift due to lower radio continuum flux densities, high radio frequency interference, and higher telescope system temperatures at low frequencies.

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arXiv2019

An ATCA Survey of HI Absorption in the Magellanic Clouds I: HI Gas Temperature Measurements in the Small Magellanic Cloud

We present the first results from the Small Magellanic Cloud portion of a new Australia Telescope Compact Array (ATCA) HI absorption survey of both of the Magellanic Clouds, comprising over 800 hours of observations. Our new HI absorption line data allow us to measure the temperature and fraction of cold neutral gas in a low metallicity environment. We observed 22 separate fields, targeting a total of 55 continuum sources against 37 of which we detected HI absorption; from this we measure a column density weighted mean average spin temperature of $ =150$ K. Splitting the spectra into individual absorption line features, we estimate the temperatures of different gas components and find an average cold gas temperature of $\sim{30}$ K for this sample, lower than the average of $\sim{40}$ K in the Milky Way. The HI appears to be evenly distributed throughout the SMC and we detect absorption in $67\%$ of the lines of sight in our sample, including some outside the main body of the galaxy ($N_{\text{HI}}>2\times{10^{21}}$ cm$^{-2}$). The optical depth and temperature of the cold neutral atomic gas shows no strong trend with location spatially or in velocity. Despite the low metallicity environment, we find an average cold gas fraction of $\sim{20\%}$, not dissimilar from that of the Milky Way.

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arXiv2019

The EDGE-CALIFA Survey: Exploring the Star Formation Law through Variable Selection

We present a multilinear analysis to determine the significant predictors of star formation in galaxies using the combined EDGE-CALIFA sample of galaxies. We analyze 1845 kpc-scale lines of sight across 39 galaxies with molecular line emission measurements from EDGE combined with optical IFU data drawn from CALIFA. We use the Least Absolute Shrinkage and Selection Operator (LASSO) to identify significant factors in predicting star formation rates. We find that the local star formation rate surface density is increased by higher molecular gas surface densities and stellar surface densities. In contrast, we see lower star formation rates in systems with older stellar populations, higher gas- and stellar-phase metallicities and larger galaxy masses. We also find a significant increase in star formation rate with galactocentric radius normalized by the disk scale length, which suggests additional parameters regulating star formation rate not explored in this study.

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