A View of the M81 Galaxy Group via the Hα Window

Караченцев, И. Д.; Кайсин, С. С.

doi:10.1086/512127

Cited by 67 publications

(97 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For a detailed analysis of Hα data see (Karachentsev & Kaisin 2007;. The Hα data were processed exactly the same way (foreground subtraction, smoothing to HI map resolution, geometrical alignment) as the FUV data.…”

Section: Estimation Of the Star Formation Ratementioning

confidence: 99%

Cold H i in faint dwarf galaxies

Patra

Chengalur

Караченцев

et al. 2015

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

We present the results of a study of the amount and distribution of cold atomic gas, as well its correlation with recent star formation in a sample of extremely faint dwarf irregular galaxies. Our sample is drawn from the Faint Irregular Galaxy GMRT Survey (FIGGS) and its extension, FIGGS2. We use two different methods to identify cold atomic gas. In the first method, line-of-sight HI spectra were decomposed into multiple Gaussian components and narrow Gaussian components were identified as cold HI . In the second method, the brightness temperature (T B ) is used as a tracer of cold HI . We find that the amount of cold gas identified using the T B method is significantly larger than the amount of gas identified using Gaussian decomposition. We also find that a large fraction of the cold gas identified using the T B method is spatially coincident with regions of recent star formation, although the converse is not true. That is only a small fraction of the regions with recent star formation are also covered by cold gas. For regions where the star formation and the cold gas overlap, we study the relationship between the star formation rate density and the cold HI column density. We find that the star formation rate density has a power law dependence on the HI column density, but that the slope of this power law is significantly flatter than that of the canonical Kennicutt-Schmidt relation.

show abstract

Section: Estimation Of the Star Formation Ratementioning

confidence: 99%

Cold H i in faint dwarf galaxies

Patra

Chengalur

Караченцев

et al. 2015

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The evolution of global star formation can be qualitatively studied in a plane of two dimensionless parameters, p = log(SFR T 0 /L B ) and f = log[M HI /(SFR T 0 )], where L B denotes the total blue luminosity of a galaxy and T 0 = 13.7 Gyr the age of the Universe. The former parameter (p) characterizes the past, and the latter ( f ) the future of the galactic star formation (see Karachentsev & Kaisin 2007 for details). We calculated the values of L B for dwarfs from the absolute B-magnitude given in Mateo (1998) or, if unavailable, from the LEDA database.…”

Section: Sfr Evolutionmentioning

confidence: 99%

Magnetic fields in Local Group dwarf irregulars

Chyży

Weżgowiec

Beck

et al. 2011

A&A

116

150

View full text Add to dashboard Cite

Aims. We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64 GHz. Three galaxies were detected. A higher frequency (4.85 GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Results. Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of <4.2 ± 1.8 μG, three times lower than in the normal spirals. The strongest field among all LG dwarfs of 10 μG (at 2.64 GHz) is observed in the starburst dwarf IC 10. The production of total magnetic fields in dwarf systems appears to be regulated mainly by the star-formation surface density (with the power-law exponent of 0.30 ± 0.04) or by the gas surface density (with the exponent 0.47 ± 0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91 ± 0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8 nG out to a distance of 160-530 kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1 μG within about a 5 kpc distance. Conclusions. Strong magnetic fields (>6 μG) are observed only in dwarfs of extreme characteristics (e.g. NGC 4449, NGC 1569, and the LG dwarf IC 10). They are all starbursts and more evolved objects of statistically much higher metallicity and global star-formation rate than the majority of the LG dwarf population. Typical LG dwarfs are unsuitable objects for the efficient supply of magnetic fields to the intergalactic medium.

show abstract

“…In addition, some of the dSphs appear to have bluer stars that probably belong to a younger main sequence. The dwarfs in our sample are classified as dSphs (Karachentsev et al 2004), with the exception of KDG 61, KDG 64, DDO 71, and HS 117 which are classified as transition-types (dIrr / dSph) as they have detectable HI content (Huchtmeier & Skillman 1998;Boyce et al 2001) or Hα emission (Karachentsev & Kaisin 2007;Karachentsev et al 2006). …”

Section: Color-magnitude Diagramsmentioning

confidence: 99%

“…The M 81 group dSphs that seem to lie in this apparent transition region are KDG 61, KDG 64, DDO 44 and DDO 71. Out of these four objects, three are classified as transition-types, namely, KDG 61, KDG 64 and DDO 71 (Karachentsev & Kaisin 2007;Boyce et al 2001) based on HI detections and Hα emission. Also among the dwarfs that coincide with the LG dSph locus, one dwarf is classified as transition-type, namely HS 117, with HI associated with it (Huchtmeier & Skillman 1998;Karachentsev et al 2006).…”

Section: Luminosity-metallicity Relationmentioning

confidence: 99%

Dwarf spheroidals in the M 81 group – Metallicity distribution functions and population gradients

Lianou

Grebel

Koch³

2010

A&A

View full text Add to dashboard Cite

Aims. We study the dwarf spheroidal galaxies in the nearby M 81 group in order to construct their photometric metallicity distributions and to investigate the potential presence of population gradients. We select all the dwarf spheroidals with available Hubble Space Telescope / Advanced Camera for Surveys archival observations, nine in total. Methods. We interpolate isochrones so as to assign a photometric metallicity to each star within a selection box in the color-magnitude diagram of each dwarf galaxy. We assume that the dwarf spheroidals contain mainly an old stellar population. In order to search for metallicity gradients, we examine the spatial distribution of two stellar populations that we separate according to their metallicities. Results. As a result, we present the photometric metallicity distribution functions, the cumulative histograms and smoothed density maps of the metal-poor and metal-rich stars as well as of the intermediate-age stars. Conclusions. From our photometric data we find that all the dwarf spheroidals show a wide range in metallicities, with mean values that are typical for old and metal-poor systems, with the exception of one dwarf spheroidal, namely IKN. Some of our dwarf spheroidals exhibit characteristics of transition-type dwarfs. Compared to the Local Group transition type dwarfs, the M 81 group ones appear to have mean metallicity values slightly more metal-rich at a given luminosity. All the dwarf spheroidals considered here appear to exhibit either population gradients or spatial variations in the centroids of their metal-poor and metal-rich population. In addition, there are luminous AGB stars detected in all of them with spatial distributions suggesting that they are well mixed with the old stars.

show abstract

A View of the M81 Galaxy Group via the Hα Window

Cited by 67 publications

References 44 publications

Cold H i in faint dwarf galaxies

Cold H i in faint dwarf galaxies

Magnetic fields in Local Group dwarf irregulars

Dwarf spheroidals in the M 81 group – Metallicity distribution functions and population gradients

Contact Info

Product

Resources

About