scholarly journals The Cosmic Ultraviolet Baryon Survey (CUBS) – I. Overview and the diverse environments of Lyman limit systems at z < 1

2020 ◽  
Vol 497 (1) ◽  
pp. 498-520
Author(s):  
Hsiao-Wen Chen ◽  
Fakhri S Zahedy ◽  
Erin Boettcher ◽  
Thomas M Cooper ◽  
Sean D Johnson ◽  
...  
Keyword(s):  
Survey Data ◽  
Dwarf Galaxy ◽  
Diverse Range ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Multiple Ionization ◽  
Low Mass ◽  
Redshift Survey ◽  
Integral Field Spectrograph ◽  
Initial Results

ABSTRACT We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS is designed to map diffuse baryonic structures at redshift z ≲ 1 using absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy survey data. CUBS QSOs are selected based on their NUV brightness to avoid biases against the presence of intervening Lyman limit systems (LLSs) at zabs &lt; 1. We report five new LLSs of $\log \, N({\mathrm{ H} \,{\small I}})/{{\rm cm^{-2}}}\gtrsim 17.2$ over a total redshift survey path-length of $\Delta \, z_{\mathrm{ LL}}=9.3$, and a number density of $n(z)=0.43_{-0.18}^{+0.26}$. Considering all absorbers with $\log \, N({{\mathrm{ H} \,{\small I}}})/{{\rm cm^{-2}}}\gt 16.5$ leads to $n(z)=1.08_{-0.25}^{+0.31}$ at zabs &lt; 1. All LLSs exhibit a multicomponent structure and associated metal transitions from multiple ionization states such as C ii, C iii, Mg ii, Si ii, Si iii, and O vi absorption. Differential chemical enrichment levels as well as ionization states are directly observed across individual components in three LLSs. We present deep galaxy survey data obtained using the VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching sensitivities necessary for detecting galaxies fainter than $0.1\, L_*$ at d ≲ 300 physical kpc (pkpc) in all five fields. A diverse range of galaxy properties is seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating gaseous halo/disc, a star-forming galaxy, a massive quiescent galaxy, to a galaxy group. The closest galaxies have projected distances ranging from d = 15 to 72 pkpc and intrinsic luminosities from ${\approx} 0.01\, L_*$ to ${\approx} 3\, L_*$. Our study shows that LLSs originate in a variety of galaxy environments and trace gaseous structures with a broad range of metallicities.

scholarly journals The OTELO survey

2020 ◽  
Vol 636 ◽  
pp. A84 ◽  
Author(s):  
Jakub Nadolny ◽  
Maritza A. Lara-López ◽  
Miguel Cerviño ◽  
Ángel Bongiovanni ◽  
Jordi Cepa ◽  
...  
Keyword(s):  
Emission Line ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Tunable Filter ◽  
Sloan Digital Sky Survey ◽  
Minimization Method ◽  
High Resolution Data ◽  
Star Forming ◽  
Low Mass ◽  
Stellar Masses

Context. A sample of low-mass Hα emission line sources at z ∼ 0.4 was studied in the context of the mass-metallicty relation (MZR) and its possible evolution. We drew our sample from the OSIRIS Tunable Emission Line Object (OTELO) survey, which exploits the red tunable filter of OSIRIS at the Gran Telescopio Canarias to perform a blind narrow-band spectral scan in a selected field of the Extended Groth Strip. We were able to directly measure emission line fluxes and equivalent widths from the analysis of OTELO pseudo-spectra. Aims. This study aims to explore the MZR in the very low-mass regime. Our sample reaches stellar masses (M*) as low as 106.8 M⊙, where 63% of the sample have M* <  109 M⊙. We also explore the relation of the star formation rate (SFR) and specific SFR with M* and gas-phase oxygen abundances, as well as the M*-size relation and the morphological classification. Methods. The M* were estimated using synthetic rest-frame colours. Using an χ2 minimization method, we separated the contribution of [N II]λ6583 to the Hα emission lines. Using the N2 index, we separated active galactic nuclei from star-forming galaxies (SFGs) and estimated the gas metallicity. We studied the morphology of the sampled galaxies qualitatively (visually) and quantitatively (automatically) using high-resolution data from the Hubble Space Telescope-ACS. The physical size of the galaxies was derived from the morphological analysis using GALAPAGOS2/GALFIT, where we fit a single-Sérsic 2D model to each source. Results. We find no evidence for an MZR evolution from comparing our very low-mass sample with local SFGs from the Sloan Digital Sky Survey. Furthermore, the same is true for M*-size and M*-SFR relations, as we deduce from comparison with recent literature. Morphologically, our sample is mostly (63%) populated by late-type galaxies, with 13% of early-type sources. For the first time, we identify one possible candidate outlier in the MZR at z = 0.4. The stellar-mass, metallicity, colour, morphology, and SFR of this source suggest that it is compatible with a transitional dwarf galaxy.

scholarly journals Evidence for an accreting massive black hole in He 2–10 from adaptive optics integral field spectroscopy

2020 ◽  
Vol 494 (2) ◽  
pp. 2004-2011 ◽  
Author(s):  
Rogemar A Riffel
Keyword(s):  
Black Hole ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Dwarf Galaxy ◽  
Line Emission ◽  
Massive Black Hole ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integral Field Spectrograph ◽  
Integral Field

ABSTRACT Henize 2–10 is a blue dwarf galaxy with intense star formation and one the most intriguing question about it is whether or not it hosts an accreting massive black hole. We use H and K-band integral field spectra of the inner 130 pc × 130 pc of He 2–10 to investigate the emission and kinematics of the gas at unprecedented spatial resolution. The observations were done using the Gemini Near-Infrared Integral Field Spectrograph (NIFS) operating with the ALTAIR adaptive optics module and the resulting spatial resolutions are 6.5 and 8.6 pc in the K and H bands, respectively. Most of the line emission is due to excitation of the gas by photoionization and shocks produced by the star forming regions. In addition, our data provide evidence of emission of gas excited by an active galactic nucleus located at the position of the radio and X-ray sources, as revealed by the analysis of the emission-line ratios. The emission lines from the ionized gas in the field present two kinematic components: one narrow with a velocity field suggesting a disc rotation and a broad component due to winds from the star forming regions. The molecular gas shows only the narrow component. The stellar velocity dispersion map presents an enhancement of about 7 km s−1 at the position of the black hole, consistent with a mass of $1.5^{+1.3}_{-1.3}\times 10^6$ M⊙.

scholarly journals Properties of barred galaxies in the MaNGA galaxy survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 226-230
Author(s):  
Amelia Fraser-McKelvie ◽  
Michael Merrifield ◽  
Alfonso Aragón-Salamanca ◽  
Karen Masters ◽  
Keyword(s):  
Main Sequence ◽  
High Mass ◽  
Star Forming ◽  
Barred Galaxies ◽  
Wide Range ◽  
The Galaxy ◽  
Hα Emission ◽  
Low Mass ◽  
Formation And Evolution ◽  
Initial Results

AbstractWe present the initial results of a census of 684 barred galaxies in the MaNGA galaxy survey. This large sample contains galaxies with a wide range of physical properties, and we attempt to link bar properties to key observables for the whole galaxy. We find the length of the bar, when normalised for galaxy size, is correlated with the distance of the galaxy from the star formation main sequence, with more passive galaxies hosting larger-scale bars. Ionised gas is observed along the bars of low-mass galaxies only, and these galaxies are generally star-forming and host short bars. Higher-mass galaxies do not contain Hα emission along their bars, however, but are more likely to host rings or Hα at the centre and ends of the bar. Our results suggest that different physical processes are at play in the formation and evolution of bars in low- and high-mass galaxies.

scholarly journals Photometric Structure and Star Formation in Blue Compact Dwarf Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 327-327
Author(s):  
P. Papaderos
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Host Galaxy ◽  
Star Forming ◽  
Formation History ◽  
Low Surface Brightness ◽  
Low Mass

The star-formation history and chemodynamical evolution of Blue Compact Dwarf (BCD) galaxies are central issues in dwarf galaxy research. In spite of being old in their vast majority, BCDs resemble in many aspects unevolved low-mass galaxies in the early universe. They are gas-rich (Hi mass fraction of typically > 30%) and metal-deficient (7.1 $\la$ 12+log(O/H) $\la$ 8.3) extragalactic systems, undergoing intense star-forming (SF) activity within an underlying low-surface brightness (LSB) host galaxy.

scholarly journals The dwarf galaxy population as revealed by ALFALFA

2018 ◽  
Vol 14 (S344) ◽  
pp. 464-467
Author(s):  
Elizabeth A. K. Adams ◽  
Catherine Ball ◽  
John M. Cannon ◽  
Martha P. Haynes ◽  
Alec Hirschauer ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Optical Counterpart ◽  
Star Forming ◽  
Large Numbers ◽  
Low Surface Brightness ◽  
Low Mass ◽  
Galaxy Population ◽  
Optical Surveys

AbstractThe combination of sensitivity and large sky coverage of the ALFALFA HI survey has enabled the detection of difficult to observe low mass galaxies in large numbers, including dwarf galaxies overlooked in optical surveys. Three different, but connected, studies of dwarf galaxies from the ALFALFA survey are of particular interest: SHIELD (Survey of HI in Extremely Low-mass Dwarfs), candidate gas-rich ultra-faint dwarf galaxies, and the (Almost) Dark population. SHIELD is a systematic multiwavelength study of all dwarf galaxies from ALFALFA with MHI < 107.2M⊙ and clear optical counterparts. Candidate gas-rich ultra-faint dwarf galaxies extend the dwarf galaxy population to even lower masses. These galaxies are identified as isolated HI clouds with no discernible optical counterpart but subsequent observations reveal that some are extremely faint, gas-dominated galaxies. Leo P, discovered first as an HI detection, and then found to be an actively star-forming galaxy, bridges the gap between these candidate galaxies and the SHIELD sample. The (Almost) Dark sample consists of galaxies whose optical counterparts are overlooked in current optical surveys but which are clear detections in ALFALFA. This sample includes field gas-rich ultra-diffuse galaxies. Coma P, with a peak surface brightness of only ∼26.4 mag arcsec−2 in g’, demonstrates the sort of extreme low surface brightness galaxy that can be discovered in an HI survey.

Overview and initial results of the National Center for Health Statistics’ Research and Development Survey1

2020 ◽  
Vol 36 (4) ◽  
pp. 1199-1211
Author(s):  
Jennifer Parker ◽  
Kristen Miller ◽  
Yulei He ◽  
Paul Scanlon ◽  
Bill Cai ◽  
...  
Keyword(s):  
Survey Data ◽  
Evaluation Studies ◽  
Research Area ◽  
Production Cycle ◽  
Response Patterns ◽  
Health Statistics ◽  
Mode Effects ◽  
Research Areas ◽  
Statistical Agencies ◽  
Initial Results

The National Center for Health Statistics is assessing the usefulness of recruited web panels in multiple research areas. One research area examines the use of close-ended probe questions and split-panel experiments for evaluating question-response patterns. Another research area is the development of statistical methodology to leverage the strength of national survey data to evaluate, and possibly improve, health estimates from recruited panels. Recruited web panels, with their lower cost and faster production cycle, in combination with established population health surveys, may be useful for some purposes for statistical agencies. Our initial results indicate that web survey data from a recruited panel can be used for question evaluation studies without affecting other survey content. However, the success of these data to provide estimates that align with those from large national surveys will depend on many factors, including further understanding of design features of the recruited panel (e.g. coverage and mode effects), the statistical methods and covariates used to obtain the original and adjusted weights, and the health outcomes of interest.

Bidimensional Spectroscopic Mapping and Chemical Abundances of the Star‐forming Dwarf Galaxy I Zw 18

1998 ◽  
Vol 508 (1) ◽  
pp. 248-261 ◽  
Author(s):  
José M. Vílchez ◽  
Jorge Iglesias‐Páramo
Keyword(s):  
Dwarf Galaxy ◽  
Chemical Abundances ◽  
Star Forming

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

1998 ◽  
Vol 11 (1) ◽  
pp. 423-424
Author(s):  
Motohide Tamura ◽  
Yoichi Itoh ◽  
Yumiko Oasa ◽  
Alan Tokunaga ◽  
Koji Sugitani
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
T Tauri Stars ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Star Forming ◽  
Star Forming Regions ◽  
T Tauri ◽  
Low Mass ◽  
Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

scholarly journals Modelling H2 and its effects on star formation using a joint implementation of gadget-3 and KROME

2021 ◽  
Vol 504 (2) ◽  
pp. 2325-2345
Author(s):  
Emanuel Sillero ◽  
Patricia B Tissera ◽  
Diego G Lambas ◽  
Stefano Bovino ◽  
Dominik R Schleicher ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Physical Parameters ◽  
Density Profiles ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Numerical Resolution ◽  
Stellar Radiation ◽  
Wide Range ◽  
The Impact

ABSTRACT We present p-gadget3-k, an updated version of gadget-3, that incorporates the chemistry package krome. p-gadget3-k follows the hydrodynamical and chemical evolution of cosmic structures, incorporating the chemistry and cooling of H2 and metal cooling in non-equilibrium. We performed different runs of the same ICs to assess the impact of various physical parameters and prescriptions, namely gas metallicity, molecular hydrogen formation on dust, star formation recipes including or not H2 dependence, and the effects of numerical resolution. We find that the characteristics of the simulated systems, both globally and at kpc-scales, are in good agreement with several observable properties of molecular gas in star-forming galaxies. The surface density profiles of star formation rate (SFR) and H2 are found to vary with the clumping factor and resolution. In agreement with previous results, the chemical enrichment of the gas component is found to be a key ingredient to model the formation and distribution of H2 as a function of gas density and temperature. A star formation algorithm that takes into account the H2 fraction together with a treatment for the local stellar radiation field improves the agreement with observed H2 abundances over a wide range of gas densities and with the molecular Kennicutt–Schmidt law, implying a more realistic modelling of the star formation process.

scholarly journals The effect of photoionizing feedback on the shaping of hierarchically-forming stellar clusters

2020 ◽  
Vol 499 (1) ◽  
pp. 668-680
Author(s):  
Alejandro González-Samaniego ◽  
Enrique Vazquez-Semadeni
Keyword(s):  
Star Formation ◽  
Early Stage ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Transfer Scheme ◽  
Star Forming ◽  
Secondary Star ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT We use two hydrodynamical simulations (with and without photoionizing feedback) of the self-consistent evolution of molecular clouds (MCs) undergoing global hierarchical collapse (GHC), to study the effect of the feedback on the structural and kinematic properties of the gas and the stellar clusters formed in the clouds. During this early stage, the evolution of the two simulations is very similar (implying that the feedback from low-mass stars does not affect the cloud-scale evolution significantly) and the star-forming region accretes faster than it can convert gas into stars, causing the instantaneous measured star formation efficiency (SFE) to remain low even in the absence of significant feedback. Afterwards, the ionizing feedback first destroys the filamentary supply to star-forming hubs and ultimately removes the gas from it, thus first reducing the star formation (SF) and finally halting it. The ionizing feedback also affects the initial kinematics and spatial distribution of the forming stars because the gas being dispersed continues to form stars, which inherit its motion. In the non-feedback simulation, the groups remain highly compact and do not mix, while in the run with feedback, the gas dispersal causes each group to expand, and the cluster expansion thus consists of the combined expansion of the groups. Most secondary star-forming sites around the main hub are also present in the non-feedback run, implying a primordial rather than triggered nature. We do find one example of a peripheral star-forming site that appears only in the feedback run, thus having a triggered origin. However, this appears to be the exception rather than the rule, although this may be an artefact of our simplified radiative transfer scheme.

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