H i-MaNGA: H i follow-up for the MaNGA survey Masters, Karen L; Stark, David V; Pace, Zachary J ...
Monthly Notices of the Royal Astronomical Society,
09/2019, Letnik:
488, Številka:
3
Journal Article
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Abstract
We present the H i-MaNGA programme of H i follow-up for the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. MaNGA, which is part of the Fourth phase of the Sloan Digital ...Sky Surveys, is in the process of obtaining integral field unit spectroscopy for a sample of ∼10 000 nearby galaxies. We give an overview of the H i 21cm radio follow-up observing plans and progress and present data for the first 331 galaxies observed in the 2016 observing season at the Robert C. Bryd Green Bank Telescope. We also provide a cross-match of the current MaNGA (DR15) sample with publicly available H i data from the Arecibo Legacy Fast Arecibo L-band Feed Array survey. The addition of H i data to the MaNGA data set will strengthen the survey’s ability to address several of its key science goals that relate to the gas content of galaxies, while also increasing the legacy of this survey for all extragalactic science.
A galaxy's stellar mass is one of its most fundamental properties, but it remains challenging to measure reliably. With the advent of very large optical spectroscopic surveys, efficient methods that ...can make use of low signal-to-noise spectra are needed. With this in mind, we created a new software package for estimating effective stellar mass-to-light ratios that uses a principal component analysis (PCA) basis set to optimize the comparison between observed spectra and a large library of stellar population synthesis models. In Paper I, we showed that with a set of six PCA basis vectors we could faithfully represent most optical spectra from the Mapping Nearby Galaxies at APO (MaNGA) survey, and we tested the accuracy of our M/L estimates using synthetic spectra. Here, we explore sources of systematic error in our mass measurements by comparing our new measurements to data from the literature. We compare our stellar mass surface density estimates to kinematics-derived dynamical mass surface density measurements from the DiskMass Survey and find some tension between the two that could be resolved if the disk scale heights used in the kinematic analysis were overestimated by a factor of ∼1.5. We formulate an aperture-corrected stellar mass catalog for the MaNGA survey, and compare to previous stellar mass estimates based on multiband optical photometry, finding typical discrepancies of 0.1 dex. Using the spatially resolved MaNGA data, we evaluate the impact of estimating total stellar masses from spatially unresolved spectra, and we explore how the biases that result from unresolved spectra depend upon the galaxy's dust extinction and star formation rate. Finally, we describe an SDSS Value-Added Catalog that will include both spatially resolved and total (aperture-corrected) stellar masses for MaNGA galaxies.
Gas interior to the bar of the Milky Way has recently been shown to be the closest example of a low-ionization (nuclear) emission region (LI(N)ER) in the universe. To better understand the nature of ...this gas, a sample of face-on galaxies with integral field spectroscopy is used to study the ionized gas conditions of 240 barred and 250 nonbarred galaxies, focusing on those that are most similar to the Milky Way. Strong optical line emission of N ii λ6584, H , O iii λ5007, and Hβ are used to diagnose the dominant ionization mechanisms of gas across galaxies and the Galaxy via Baldwin-Phillips-Terlevich diagrams. Barred galaxies show a strong suppression of star formation and an increase in composite and LI(N)ER-like spectra in their inner regions when compared with similar nonbarred counterparts. This effect is lessened in galaxies of very low ( ) or very high ( ) total stellar mass. Bar masks from Galaxy Zoo:3D show the bar's nonaxisymmetric effect on the ionized gas and help predict the face-on distribution of ionized gas conditions near the bar of the Milky Way.
We evaluated acute turbidity effects on a threatened coral species (Orbicella faveolata) under three short-term challenge scenarios using a Port of Miami sediment homogenate to simulate turbid ...conditions during dredging. For these experiments we designed a simple coral challenge test system that kept turbidity stable, without adverse effects to the coral. A 96-h coral challenge experiment demonstrated that low turbidity levels (≥4 NTU) have negative effects on O. faveolata tissue regeneration. A 48-h turbidity exposure (maximum 30 NTU) had no effect on O. faveolata tissue regeneration, showing that short term turbidity exposures may not be detrimental to coral health. In a 13-day test, treated coral fragments (maximum 30 NTU) exhibited significant delays in tissue regeneration, but recovery was observed after approximately one week. The results presented here can be used to inform management decisions for proposed dredging activities proximal to coral reef habitats.
•A simple turbidity dosing system was designed and tested.•Turbidity at 4 NTU impeded coral tissue regeneration after a 96-h exposure.•A 48-h exposure at 30 NTU had no effect on coral wound healing.•A 13-day turbidity exposure (30 NTU) delayed tissue regeneration by 2.4 days.
Abstract
Bars may induce morphological features, such as rings, through their resonances. Previous studies suggested that the presence of “dark gaps,” or regions of a galaxy where the difference ...between the surface brightness along the bar major axis and that along the bar minor axis is maximal, can be attributed to the location of bar corotation. Here, using GALAKOS, a high-resolution
N
-body simulation of a barred galaxy, we test this photometric method’s ability to identify the bar corotation resonance. Contrary to previous work, our results indicate that “dark gaps” are a clear sign of the location of the 4:1 ultraharmonic resonance instead of bar corotation. Measurements of the bar corotation can indirectly be inferred using kinematic information, e.g., by measuring the shape of the rotation curve. We demonstrate our concept on a sample of 578 face-on barred galaxies with both imaging and integral field observations and find that the sample likely consists primarily of fast bars.
Gaseous inflows are necessary suppliers of galaxies' star-forming fuel, but are difficult to characterize at the survey scale. We use integral-field spectroscopic measurements of gas-phase ...metallicity and single-dish radio measurements of total atomic gas mass to estimate the magnitude and frequency of gaseous inflows incident on star-forming galaxies. We reveal a mutual correlation between steep oxygen abundance profiles between 0.25 and 1.5 Re, increased variability of metallicity between 1.25 and 1.75 Re, and elevated H i content at fixed total galaxy stellar mass. Employing a simple but intuitive inflow model, we find that galaxies with total stellar mass less than 1010.1 M have local oxygen abundance profiles consistent with reinvigoration by inflows. Approximately 10%-25% of low-mass galaxies possess signatures of recent accretion, with estimated typical enhancements of approximately 10%-90% in local gas mass surface density. Higher-mass galaxies have limited evidence for such inflows. The large diversity of H i mass implies that inflow-associated gas ought to reside far from the star-forming disk. We therefore propose that a combination of high H i mass, steep metallicity profile between 0.25 and 1.5 Re, and wide metallicity distribution function between 1.25 and 1.75 Re be employed to target possible hosts of inflowing gas for high-resolution radio follow-up.
We present a method of fitting optical spectra of galaxies using a basis set of six vectors obtained from principal-component analysis of a library of synthetic spectra of 40,000 star formation ...histories (SFHs). Using this library, we provide estimates of the resolved effective stellar mass-to-light ratio ( ) for thousands of galaxies from the SDSS-IV/MaNGA integral-field spectroscopic survey. Using a testing framework built on additional synthetic SFHs, we show that the estimates of are reliable (as are their uncertainties) at a variety of signal-to-noise ratios, stellar metallicities, and dust attenuation conditions. Finally, we describe the future release of the resolved stellar mass-to-light ratios as an SDSS-IV/MaNGA Value-Added Catalog and provide a link to the software used to conduct this analysis. (The software can be found at https://github.com/zpace/pcay.)
Throughout their lives, galaxies form stars from their supply of cold gas: the largest of those stars generate heavy elements in their interiors prior to their explosive demise. As the heavy elements ...created in stellar evolution continually build with each generation of star formation, so do the generations of long-lived, low-mass stars. A galaxy's metal content and its total mass in stars together indicate the state of the galaxy's underlying gas reservoir: the reservoir is depleted by star formation and feedback, and is thought to be rejuvenated by inflows of low-metallicity gas from filaments of the cosmic web. However, the buildup of stellar mass is difficult to measure precisely: the observational degeneracies between stars with different ages and metallicities bring about troublesome systematics. In addition, there is little direct evidence for inflows in the local universe, though they are present in simulations and seem to be necessary to maintain gas reservoirs' star-forming vigor. In this dissertation, I develop and refine a method of measuring stellar mass-to-light ratio and other stellar population properties from medium-resolution optical spectroscopy. This method builds on a library of model star-formation histories and their associated synthetic optical spectra, and constructs a low-dimensional spectroscopic basis set capable of maximizing the predictive power of observations. This method is tested and deployed on resolved, integral-field spectroscopic observations from the SDSS-IV/MaNGA survey of nearly 10,000 nearby galaxies. Finally, I produce and release a catalog of resolved stellar mass maps and of aperture-corrected total galaxy stellar masses. I also measure resolved gas-phase metallicities in the MaNGA survey, and relate them to the mass of the galaxy-wide gas reservoir. A mutual correlation is uncovered between a steep radial metallicity profile, a large dispersion in the metallicity profile between 1.25-1.75 galaxy disk effective radii, and a large HI mass fraction relative to galaxies of the same total stellar mass. The first axis of that correlation is consistent with theoretical predictions of the signatures of radial gas flows, so I test a simple, but intuitive model of a gaseous inflow, whereby ambient metallicity is "diluted" by low-metallicity gas introduced from elsewhere. This yields estimates of the possible impact of gaseous inflows on local star-forming gas reservoirs; and indicates a means towards selecting potential inflow hosts for radio follow-up.
The Sloan Digital Sky Surveys (SDSS) have been observing the skies from Apache Point Observatory (APO) since 1998 (using the 2.5m Sloan Foundation Telescope, Gunn et al. 2006) and from Las Campanas ...Observatory (LCO) since 2017 (using the du Pont 2.5m Telescope). Representing the fourth phase of SDSS, SDSS-IV (Blanton et al. 2017) consists of three main surveys; the Extended Baryon Oscillation Spectroscopic Survey (eBOSS; Dawson et al. 2016), Mapping Nearby Galaxies at APO (MaNGA; Bundy et al. 2015), and the APO Galactic Evolution Experiment 2 (APOGEE-2; Majewski et al. 2017). Within eBOSS, SDSS-IV has also conducted two smaller programs: the SPectroscopic IDentification of ERosita Sources (SPIDERS; Clerc et al. 2016; Dwelly et al. 2017) and the Time Domain Spectroscopic Survey (TDSS; Morganson et al. 2015). These programs have investigated a broad range of cosmological scales, including cosmology with large-scale structure in eBOSS, the population of quasars and variable or X-ray-emitting stars with TDSS and SPIDERS; nearby galaxies in MaNGA; and the Milky Way and its stars in APOGEE-2.
Bars may induce morphological features, such as rings, through their resonances. Previous studies suggested that the presence of 'dark-gaps', or regions of a galaxy where the difference between the ...surface brightness along the bar major axis and along the bar minor axis are maximal, can be attributed to the location of bar corotation. Here, using GALAKOS, a high-resolution N-body simulation of a barred galaxy, we test this photometric method's ability to identify the bar corotation resonance. Contrary to previous work, our results indicate that 'dark-gaps' are a clear sign of the location of the 4:1 ultra-harmonic resonance instead of bar corotation. Measurements of the bar corotation can indirectly be inferred using kinematic information, e.g., by measuring the shape of the rotation curve. We demonstrate our concept on a sample of 578 face-on barred galaxies with both imaging and integral field observations and find the sample likely consists primarily of fast bars.
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